[Federal Register Volume 89, Number 73 (Monday, April 15, 2024)]
[Proposed Rules]
[Pages 26704-26754]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-07646]



[[Page 26703]]

Vol. 89

Monday,

No. 73

April 15, 2024

Part V





Department of Transportation





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National Highway Traffic Safety Administration





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49 CFR Part 571





Federal Motor Vehicle Safety Standards; FMVSS No. 305a Electric-Powered 
Vehicles: Electric Powertrain Integrity Global Technical Regulation No. 
20, Incorporation by Reference; Proposed Rule

  Federal Register / Vol. 89 , No. 73 / Monday, April 15, 2024 / 
Proposed Rules  

[[Page 26704]]


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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. NHTSA-2024-0012]
RIN 2127-AM43


Federal Motor Vehicle Safety Standards; FMVSS No. 305a Electric-
Powered Vehicles: Electric Powertrain Integrity Global Technical 
Regulation No. 20, Incorporation by Reference

AGENCY: National Highway Traffic Safety Administration (NHTSA), 
Department of Transportation (DOT).

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: Consistent with a Global Technical Regulation on electric 
vehicle safety, NHTSA proposes to establish Federal Motor Vehicle 
Safety Standard (FMVSS) No. 305a to replace FMVSS No. 305, ``Electric-
powered vehicles: Electrolyte spillage and electrical shock 
protection.'' Among other improvements, FMVSS No. 305a would apply to 
light and heavy vehicles and would have performance and risk mitigation 
requirements for the propulsion battery. Relating to a National 
Transportation Safety Board recommendation, FMVSS No. 305a would also 
require manufacturers to submit standardized emergency response 
information for inclusion on NHTSA's website that would assist first 
and second responders handling electric vehicles.

DATES: Comments should be submitted no later than June 14, 2024.
    Proposed compliance date: We propose that the compliance date for 
the proposed requirements be two years after the date of publication of 
the final rule in the Federal Register. Small-volume manufacturers, 
final-stage manufacturers, and alterers would be provided an additional 
year to comply with the rule beyond the date identified above. We 
propose to permit optional early compliance with the rule. After FMVSS 
No. 305a is finalized, NHTSA intends to sunset FMVSS No. 305.

ADDRESSES: You may submit comments identified by the docket number in 
the heading of this document or by any of the following methods:
     Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments on 
the electronic docket site by clicking on ``Help'' or ``FAQ.''
     Mail: Docket Management Facility. M-30, U.S. Department of 
Transportation, 1200 New Jersey Avenue SE, West Building, Ground Floor, 
Room W12-140, Washington, DC 20590.
     Hand Delivery: U.S. Department of Transportation, 1200 New 
Jersey Avenue SE, West Building, Ground Floor, Room W12-140, 
Washington, DC 20590 between 9 a.m. and 5 p.m. Eastern Time, Monday 
through Friday, except Federal Holidays.
     Fax: 202-493-2251.
    Instructions: All submissions must include the agency name and 
docket number. Note that all comments received will be posted without 
change to http://www.regulations.gov, including any personal 
information provided. Please see the Privacy Act discussion below. We 
will consider all comments received before the close of business on the 
comment closing date indicated above. To the extent possible, we will 
also consider comments filed after the closing date.
    Docket: For access to the docket to read background documents or 
comments received, go to www.regulations.gov at any time or to 1200 New 
Jersey Avenue SE, West Building Ground Floor, Room W12-140, Washington, 
DC 20590, between 9 a.m. and 5 p.m., Monday through Friday, except 
Federal Holidays. Telephone: 202-366-9826.
    Confidential Business Information: If you claim that any of the 
information in your comment (including any additional documents or 
attachments) constitutes confidential business information within the 
meaning of 5 U.S.C. 552(b)(4) or is protected from disclosure pursuant 
to 18 U.S.C. 1905, please see the detailed instructions given under the 
Public Participation heading of the SUPPLEMENTARY INFORMATION section 
of this document.
    Privacy Act: In accordance with 5 U.S.C. 553(c), DOT solicits 
comments from the public to better inform its decision-making process. 
DOT posts these comments, without edit, including any personal 
information the commenter provides, to www.regulations.gov, as 
described in the system of records notice (DOT/ALL-14 FDMS), which can 
be reviewed at www.transportation.gov/privacy. In order to facilitate 
comment tracking and response, we encourage commenters to provide their 
name, or the name of their organization; however, submission of names 
is completely optional. Whether or not commenters identify themselves, 
all timely comments will be fully considered.

FOR FURTHER INFORMATION CONTACT: For technical issues, you may contact 
Ms. Lina Valivullah, Office of Crashworthiness Standards; Telephone: 
202-366-8786; Email: [email protected]; Facsimile: (202) 493-
2739. For legal issues, you may contact Ms. K. Helena Sung, Office of 
Chief Counsel; Telephone: 202-366-2992; Email: [email protected]; 
Facsimile: (202) 366-3820. The mailing address of these officials is: 
National Highway Traffic Safety Administration, 1200 New Jersey Avenue 
SE, Washington, DC 20590.

SUPPLEMENTARY INFORMATION: 

Table of Contents

I. Executive Summary
II. Background
    a. Overview of FMVSS No. 305
    b. Overview of GTR No. 20
    1. The GTR Process
    2. GTR No. 20
III. Proposals Based on GTR No. 20
    a. Expanding Applicability of FMVSS No. 305a to Heavy Vehicles
    1. Heavy School Buses
    2. Heavy Vehicles Other Than School Buses
    i. Request for Comment; Mechanical Integrity Test
    ii. Request for Comment; Mechanical Shock Test
    b. General Specifications Relating To Crash Testing
    1. Low Energy Option for Capacitors
    2. Assessing Fire or Explosion in Vehicle Post-Crash Test
    3. Assessing Post-Crash Voltage Measurements
    4. Electrolyte Spillage Versus Leakage
    c. REESS Requirements Applicable to All Vehicles
    1. Vehicle Controls for Safe REESS Operation
    i. Overcharge Protection
    ii. Over-Discharge Protection
    iii. Overcurrent Protection
    iv. Over-Temperature Protection
    v. External Short-Circuit Protection
    vi. Low-Temperature Protection
    2. Mitigating Risk of Thermal Propagation Due to Internal Short 
Within a Single Cell in the REESS
    i. Safety Need
    ii. GTR No. 20 Phase 1 Requirements
    iii. NHTSA Proposal
    3. Warning Requirements for REESS Operations
    i. Thermal Event Warning
    ii. Warning in the Event of Operational Failure of REESS Vehicle 
Controls
    4. Protection Against Water Exposure
    i. NHTSA Proposal
    A. Vehicle Washing Test
    B. Driving Through Standing Water Test
    ii. NHTSA's Consideration of Submersions
    5. Miscellaneous GTR No. 20 Provisions Not Proposed
    i. REESS Vibration Requirements
    ii. REESS Thermal Shock and Cycling
    iii. REESS Fire Resistance
    iv. Low State-of-Charge (SOC) Telltale
IV. Request for Comment on Applying FMVSS No. 305a to Low-Speed 
Vehicles
V. Emergency Response Information To Assist First and Second 
Responders

[[Page 26705]]

VI. Request for Comment on Placing the Emergency Response 
Information and Documentation Requirements in a Regulation Rather 
Than in FMVSS No. 305a
VII. Proposed Compliance Dates
VIII. Rulemaking Analyses and Notices
IX. Public Participation
X. Appendices to the Preamble
Appendix A. Table Comparing GTR No. 20, FMVSS No. 305, and FMVSS No. 
305a
Appendix B. Request for Comment on Phase 2 GTR No. 20 Approaches 
Under Consideration by the IWG

I. Executive Summary

    NHTSA is issuing this NPRM to achieve two goals. First, NHTSA 
proposes to establish FMVSS No. 305a, ``Electric-powered Vehicles: 
Electric Powertrain Integrity,'' to upgrade and replace existing FMVSS 
No. 305. Proposed FMVSS No. 305a would have all the requirements of 
FMVSS No. 305, but the proposed standard would expand its applicability 
to vehicles with a gross vehicle weight rating (GVWR) greater than 
4,536 kilograms (kg) (10,000 pounds (lb)) and add requirements and test 
procedures covering new aspects of electric vehicle safety, such as the 
performance and risk mitigation requirements for the propulsion 
battery, referred to as the Rechargeable Electrical Energy Storage 
System (REESS). NHTSA is also proposing requirements to ensure first 
and second responders have access to vehicle-specific information about 
extinguishing REESS fires and mitigating safety risks associated with 
stranded energy \1\ when responding to emergencies. The restructured 
and upgraded FMVSS No. 305a will facilitate future updates to the 
standard as battery technologies and charging systems continue to 
evolve. After FMVSS No. 305a is finalized, NHTSA intends to sunset 
FMVSS No. 305.
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    \1\ Stranded energy is the energy remaining inside the REESS 
after a crash or other incident.
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    The second goal is to further NHTSA's effort to harmonize the 
Federal Motor Vehicle Safety Standards under the Economic Commission 
for Europe 1998 Global Agreement (``1998 Agreement''). The efforts of 
the U.S. and other contracting parties to the 1998 Agreement culminated 
in the establishment of Global Technical Regulation (GTR) No. 20, 
``Electric Vehicle Safety.'' \2\ FMVSS No. 305 already incorporates a 
substantial portion of GTR No. 20's requirements due to a previous 
NHTSA rulemaking. In 2017, NHTSA amended FMVSS No. 305 to include 
electrical safety requirements from GTR No. 13, ``Hydrogen and fuel 
cell vehicles,'' pertaining to electric vehicle performance during 
normal vehicle operation and post-crash.\3\ Because GTR No. 13's 
provisions for electric vehicles were later incorporated into what 
would become GTR No. 20, the 2017 final rule that adopted GTR No. 13's 
provisions adopted what later became many of the requirements of GTR 
No. 20. That 2017 rulemaking, however, did not expand the applicability 
of FMVSS No. 305 to include heavy vehicles nor did it include 
requirements for the REESS. This NPRM proposes these and other GTR No. 
20 requirements.
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    \2\ GTR No. 20, https://unece.org/fileadmin/DAM/trans/main/wp29/wp29wgs/wp29gen/wp29registry/ECE-TRANS-180a20e.pdf.
    \3\ GTR No. 13 only applied to light vehicles. Normal vehicle 
operations include operating modes and conditions that can 
reasonably be encountered during typical operation of the vehicle, 
such as driving, parking, standing in traffic with vehicle in drive 
mode, and charging. Final rule, 82 FR 44950, September 27, 2017.
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High Level Summary of the Proposal

    FMVSS No. 305 currently only applies to passenger cars and to 
multipurpose passenger vehicles, trucks, and buses with a GVWR of 4,536 
kg (10,000 lb) or less (``light vehicles''). Consistent with GTR No. 
20, proposed FMVSS No. 305a expands the current applicability of FMVSS 
No. 305 to vehicles with a GVWR greater than 4,536 kg (10,000 lb) 
(``heavy vehicles''). Under proposed FMVSS No. 305a:
     Light vehicles would be subject to requirements carried 
over from FMVSS No. 305 that ensure the safety of the electrical system 
during normal vehicle operations and after a crash (post-crash).\4\ 
They would also be subject to new requirements for the REESS.
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    \4\ Current FMVSS No. 305 light vehicle post-crash test 
requirements (front, side, and rear crashes) are aligned with FMVSS 
No. 301's light vehicle post-crash test requirements.
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     Heavy vehicles would be subject to the requirements for 
electrical system safety during normal vehicle operations and to 
requirements for the REESS. However, except for heavy school buses, 
they would not be subject to post-crash requirements. This proposed 
exclusion of heavy vehicles, other than school buses, from crash tests, 
aligns with similar exclusions in FMVSS No. 301, ``Fuel system 
integrity,'' for conventional fuel vehicles and FMVSS No. 303, ``Fuel 
system integrity of compressed natural gas vehicles,'' for compressed 
natural gas vehicles.
     Heavy school buses (GVWRs greater than 4,536 kg (10,000 
lb)) \5\ would be subject to the requirements for electrical system 
safety during normal vehicle operations and to the requirements for the 
REESS, and would have to meet post-crash test requirements to ensure 
the vehicles protect against unreasonable risk of electric shock and 
risk of fire after a crash. The post-crash tests are the same tests 
described in FMVSS No. 301 for heavy school buses (impacted at any 
point and at any angle by a moving contoured barrier).
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    \5\ In the school bus safety area, stakeholders, including 
NHTSA, commonly refer to buses with a GVWR over 4,536 kg (10,000 lb) 
as ``large'' school buses.
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    The post-crash requirements of proposed FMVSS No. 305a for light 
vehicles and heavy school buses include electric shock protection 
(there are four compliance options--low voltage, electrical isolation, 
protective barrier, and low energy for capacitors \6\); REESS 
retention; electrolyte leakage; and fire safety. The requirements for 
REESS retention and electrolyte leakage are already in FMVSS No. 305, 
but this NPRM proposes to enhance some provisions consistent with GTR 
No. 20. For example, current FMVSS No. 305 does not specify that there 
must be no fire or explosion after a crash test. Electric vehicles may 
catch fire long after a collision or other occurrence resulting in a 
fault condition. To account for the potential delayed response, NHTSA 
is proposing to prohibit fire or explosion for a one-hour post-test 
period.
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    \6\ FMVSS No. 305 already includes the first three compliance 
options for electrical shock protection but not the low energy 
option that is available for capacitors in GTR No. 20. This NPRM 
would complete the alignment by proposing the low energy option for 
capacitors in FMVSS No. 305a. NHTSA had considered this option years 
ago and had decided against it. As explained in detail in sections 
below, NHTSA has changed its view on the matter after further 
considering data and analysis from the GTR.
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    A substantial portion of this NPRM focuses on safety provisions for 
the propulsion battery, the REESS. For what would be the first time in 
an FMVSS, proposed FMVSS No. 305a includes comprehensive performance 
requirements and risk mitigation strategies for the REESS. These REESS 
requirements would apply to all vehicles, regardless of GVWR. A REESS 
provides electric energy for propulsion and may include necessary 
ancillary systems for physical support, thermal management, electronic 
controls, and casings. The proposed requirements set a level of 
protection of the REESS against external fault inputs, ensure the REESS 
operations are within the manufacturer-specified functional range, and 
increase the likelihood of safe operation of the REESS and other 
electrical systems of the vehicle during

[[Page 26706]]

and after water exposure during normal vehicle operations.\7\
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    \7\ ``Normal vehicle operation'' means situations such as 
driving through a pool of standing water or exposing the vehicle to 
an automated car wash. This NPRM does not propose requirements to 
address vehicle fires due to vehicle submersions in floods and storm 
surges, as GTR No. 20 does not have specific requirements to address 
this area. NHTSA is researching this latter area.
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    Proposed FMVSS No. 305a addresses some aspects of REESS safety 
through documentation measures, consistent with GTR No. 20. 
``Documentation measures'' means a list of information provided by 
manufacturers, at NHTSA's request, that demonstrate that they 
considered, assessed, and mitigated identified risks for safe operation 
of the vehicle. These proposed documentation requirements would 
address: (a) safety risk mitigation associated with charging and 
discharging during low temperature; (b) the safety risks from thermal 
propagation in the event of single-cell thermal runaway \8\ (SCTR) due 
to an internal short-circuit of a single cell; and (c) providing a 
warning if there is a malfunction of vehicle controls that manage REESS 
safe operation. The GTR takes a documentation approach on these aspects 
of safety because of the rapidly evolving electric vehicle technologies 
and the variety of available REESS and electric vehicle designs. The 
Informal Working Group experts that drafted the GTR determined there 
currently are no objective test procedures to evaluate safety risk 
mitigation designs or the operations of warnings of a malfunction of 
vehicle controls in a manner that is not design restrictive.
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    \8\ Thermal runaway means an uncontrolled increase of cell 
temperature caused by exothermic reactions inside the cell.
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    NHTSA tentatively agrees with this approach given the current state 
of knowledge. Thus, until test procedures and performance criteria can 
be developed for all vehicle powertrain architectures, proposed FMVSS 
No. 305a would require manufacturers to submit documentation to NHTSA, 
at NHTSA's request, that identify all known safety hazards, describe 
their risk mitigation strategies for the safety hazards, and, if 
applicable, describe how they provide a warning to address a safety 
hazard.\9\ The purpose of the documentation approach is two-fold. Given 
the variation of battery design and design specific risk mitigation 
systems, the documentation requirement would be a means of assuring 
that each manufacturer has identified safety risks and safety risk 
mitigation strategies. The requirement provides a means for NHTSA to 
learn of the risks associated with the REESS, understand how the 
manufacturer is addressing the risks, and oversee those safety hazards. 
This approach is battery technology neutral, not design restrictive, 
and is intended to evolve over time as battery technologies continue to 
rapidly evolve. It is an interim measure intended to assure that 
manufacturers will identify and address the safety risks of the REESS 
until such time objective performance standards can be developed that 
can be applied to all applicable REESS designs. NHTSA would also 
acquire information from the submissions to learn about the safety of 
the REESS and potentially develop the future performance standards for 
FMVSS No. 305a. The proposed documentation requirements are based on 
the approach of GTR No. 20, but NHTSA proposes to focus the GTR's 
documentation requirements to enable the agency to obtain more targeted 
information from manufacturers.\10\
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    \9\ Section 30166 of the Vehicle Safety Act authorizes the 
Secretary of Transportation (NHTSA by delegation) the ability to 
request and inspect manufacturer records that are necessary to 
enforce the prescribed regulations.
    \10\ Given the proposed documentation specifications are more 
akin to disclosure requirements that could be issued under general 
NHTSA regulation rather than pursuant to an FMVSS with specified 
test procedures, the agency also requests comment on whether the 
proposed documentation requirements would be better placed in a 
general agency regulation than in the proposed FMVSS No. 305a.
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    As part of NHTSA's battery initiative \11\ and in response to a 
2020 NTSB recommendation,\12\ this NPRM proposes to include in FMVSS 
No. 305a a requirement that vehicle manufacturers submit to NHTSA 
emergency response guides (ERGs) and rescue sheets for each vehicle 
make, model, and model year. The purpose of the requirement is to 
provide information to first \13\ and second \14\ responders regarding 
the safe handling of the vehicle in emergencies and for towing and 
storing operations. The uploaded ERGs and rescue sheets would be 
publicly available on NHTSA's website for easy searchable access. ERGs 
and rescue sheets communicate vehicle-specific information related to 
fire, submersion, and towing, as well as the location of components in 
the vehicle that may expose the vehicle occupants or rescue personnel 
to risks, the nature of a specific function or danger, and devices or 
measures which inhibit a dangerous state.
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    \11\ https://www.nhtsa.gov/battery-safety-initiative.
    \12\ ``Safety risks to emergency responders from lithium-ion 
battery fires in electric vehicles,'' Safety Report NTSB/SR-20/01, 
PB2020-101011, National Transportation Safety Board, https://www.ntsb.gov/safety/safety-studies/Documents/SR2001.pdf.
    \13\ ``First responder'' means a person with specialized 
training such as a law enforcement officer, paramedic, emergency 
medical technician, and/or firefighter, who is typically one of the 
first to arrive and provide assistance at the scene of an emergency.
    \14\ ``Second responder'' means a worker who supports first 
responders by cleaning up a site, towing vehicles, and/or returning 
services after an event requiring first responders.
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    NHTSA would require standardized formatting of the information. The 
ERG and rescue sheet requirements would meet the layout and format 
specified in ISO-17840, ``Road vehicles--Information for first and 
second responders,'' which standardize color-coded sections in a 
specific order to help first and second responders quickly identify 
pertinent vehicle-specific rescue information. The standardized 
information would be available and understandable to first and second 
responders so they can easily refer to vehicle-specific rescue 
information en route to or at the scene of a crash or fire event and 
respond to the emergency quickly and safely.
    NHTSA believes there are no notable costs associated with this 
NPRM. This proposal closely mirrors the electrical safety provisions of 
GTR No. 20, which have been voluntarily implemented by manufacturers in 
this country. The agency believes that the proposed safety standards 
are widely implemented by manufacturers of light and heavy electric 
vehicles and heavy electric school buses. Manufacturers are also 
already providing emergency response information to the National Fire 
Protection Association (NFPA); under proposed FMVSS No. 305a they would 
just have to standardize the format and submit the information to 
NHTSA.\15\
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    \15\ Similar to the issue discussed above regarding having the 
proposed documentation requirements in a general regulation rather 
than in FMVSS No. 305a, the agency also requests comment on whether 
the proposed ERG and rescue sheet requirements would be better 
placed in a general agency regulation than in proposed FMVSS No. 
305a.
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    Lastly, current FMVSS No. 305 does not apply to vehicles that 
travel under 40 km/h (25 mph), such as low-speed vehicles.\16\ Given 
there are low-speed vehicles that are also electric-powered vehicles, 
NHTSA requests comments on the possibility of applying aspects of FMVSS 
No. 305a to low-speed vehicles to ensure a level of protection against 
shock and fire, particularly during normal vehicle operation, and to 
assure the safe operation of the REESS.
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    \16\ ``Low-speed vehicle'' is defined in 49 CFR 571.3. See also 
FMVSS No. 500, ``Low speed vehicles,'' 49 CFR 500.
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II. Background

a. Overview of FMVSS No. 305

    The purpose of FMVSS No. 305, ``Electric-powered vehicles: 
electrolyte

[[Page 26707]]

spillage and electrical shock protection,'' is to reduce deaths and 
injuries from electrical shock. The standard applies only to light 
vehicles (vehicles with a GVWR less than or equal to 4,536 (kg) (10,000 
(lb)). The standard's requirements reduce the risk of harmful electric 
shock: (a) during normal vehicle operation; \17\ and (b) in post-crash 
situations (to protect vehicle occupants, and rescue workers and others 
who may come in contact with the vehicle after a crash). The standard's 
requirements for the former protect against direct and indirect contact 
of high voltage sources during everyday operation of the vehicles. The 
focus of this ``in-use'' testing (unlike ``post-crash'' testing, 
discussed below) deals with performance criteria that would be assessed 
without first exposing the vehicle to a crash test.
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    \17\ Normal vehicle operation includes operating modes and 
conditions that can reasonably be encountered during typical 
operation of the vehicle, such as driving, parking, and standing in 
traffic, as well as charging using chargers that are compatible with 
the specific charging ports installed on the vehicle. It does not 
include conditions where the vehicle is damaged, either by a crash 
or road debris, subjected to fire or water submersion, or in a state 
where service and/or maintenance is needed or being performed.
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    Normal Vehicle Operations. FMVSS No. 305 requires vehicles to 
provide the following measures to protect against electric shock during 
normal vehicle operations. Vehicles must prevent direct contact of high 
voltage sources (those operating with voltage greater than 30 VAC or 60 
VDC) \18\; prevent indirect contact of high voltage sources; 
electrically isolate high voltage sources from the electric chassis 
(500 ohms/volt or higher for alternating current (AC) and 100 ohms/volt 
or higher for direct current (DC) sources); mitigate risk of driver 
error (indicate to the driver when the vehicle is in possible active 
driving mode at startup and when the driver is leaving the vehicle, and 
prevent vehicle movement by its own propulsion system when the vehicle 
charging system is connected to the external electric power supply).
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    \18\ VAC--volts of alternating current; VDC--volts of direct 
current.
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    Post-Crash Protections. For post-crash protections, FMVSS No. 305 
requires vehicles to meet the following provisions during and after the 
crash tests specified in the standard. FMVSS No. 305 limits electrolyte 
spillage from propulsion batteries and requires the REESS to remain 
attached to the vehicle and not enter the passenger compartment. The 
standard requires that during and after a crash test, high voltage 
sources in a vehicle must be either electrically isolated from the 
vehicle's chassis; of a voltage below specified levels considered safe 
from electric shock hazards; or prevented from direct or indirect 
contact by occupants or emergency services personnel by use of physical 
barriers. The standard specifies that the post-crash requirements must 
be met after crash tests involving: a frontal impact up to and 
including 48 kilometer per hour (km/h) (30 mile per hour (mph)) into a 
fixed collision barrier; an impact of a moving barrier at 80 km/h (50 
mph) into the rear of the vehicle; an impact of a moving barrier at 53 
km/h (33 mph) into the side of the vehicle; and under static rollover 
conditions after each such impact.
    FMVSS No. 305 already has many of GTR No. 20's requirements for 
light vehicles, including requirements for electrical safety during 
normal vehicle operation; post-crash electrolyte spillage; post-crash 
REESS retention; and most of the GTR's post-crash electrical safety 
options for high voltage sources.

b. Overview of GTR No. 20

1. The GTR Process
    The United States is a contracting party to the ``1998 Agreement'' 
(the Agreement concerning the Establishing of Global Technical 
Regulations for Wheeled Vehicles, Equipment and Parts which can be 
fitted and/or be used on Wheeled Vehicles). This agreement entered into 
force in 2000 and is administered by the UN Economic Commission for 
Europe's (UN ECE's) World Forum for the Harmonization of Vehicle 
Regulations (WP.29). The purpose of this agreement is to establish 
Global Technical Regulations (GTRs).
    In March 2012, UNECE WP.29 formally adopted the proposal to 
establish GTR No. 20 at its one-hundred-and-fifty-eighth session. NHTSA 
chaired the development of GTR No. 20 and voted in favor of 
establishing GTR No. 20.
    As a Contracting Party Member to the 1998 Global Agreement who 
voted in favor of GTR No. 20, NHTSA is obligated to initiate the 
process used in the U.S. to adopt the GTR as an agency regulation. By 
issuing this NPRM, NHTSA is initiating the process to consider adoption 
of GTR No. 20. As noted above, under the terms of the 1998 Agreement, 
NHTSA is not obligated to adopt the GTR after initiating this process. 
In deciding whether to adopt a GTR as an FMVSS, NHTSA follows the 
requirements for NHTSA rulemaking, including the Administrative 
Procedure Act, the National Traffic and Motor Vehicle Safety Act 
(Vehicle Safety Act), Presidential Executive Orders, and DOT and NHTSA 
policies, procedures, and regulations. Among other things, FMVSSs 
issued under the Vehicle Safety Act ``shall be practicable, meet the 
need for motor vehicle safety, and be stated in objective terms.'' \19\
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    \19\ 49 U.S.C. 30111.
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2. GTR No. 20
    GTR No. 20 establishes performance-orientated requirements that 
reduce potential safety risks of electric vehicles (EVs) while in use 
and after a crash event. The GTR includes provisions that address 
electrical shock associated with high voltage circuits of EVs and 
potential hazards associated with lithium-ion batteries and/or other 
REESS. One of the principles for developing GTR No. 20 was to address 
unique safety risks posed by electric vehicles and their components to 
ensure a safety level equivalent to conventional vehicles with internal 
combustion engines.
    The requirements in GTR No. 20 were developed in Phase 1 of the 
GTR. GTR No. 20 was developed in phases due to the differing stages at 
which technologies have been developed and evaluated. The informal 
working group (IWG) that developed the GTR determined that Phase 1 
would address issues relating to the safe operation of the rechargeable 
electrical energy storage system (REESS), and for mitigating risks of 
fire and other safety risks associated with the REESS. In Phase 2, 
which is on-going, the IWG is addressing issues involving long-term 
research and verification.\20\ This NPRM pertains to the adoption of 
the GTR as developed in Phase 1.
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    \20\ In Appendix B to this preamble, NHTSA requests comments on 
some issues under development in Phase 2.
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    GTR No. 20 applies to all electric-powered vehicles regardless of 
GVWR, in contrast to FMVSS No. 305, which only applies to light 
vehicles. FMVSS No. 305 currently includes the majority of GTR No. 20's 
requirements and applies these to light vehicles. GTR No. 20 also has 
safety requirements for the REESS beyond those in FMVSS No. 305. These 
additional requirements in GTR No. 20 for the REESS include:

     Safe operation of REESS under the following exposures 
during normal vehicle operations:

    [cir] REESS protection under external fault conditions and extreme 
operating temperatures:

--External short circuit
--Overcharge
--Over-discharge

[[Page 26708]]

--Overcurrent
--High operating temperature
--Low operating temperature

[cir] Management of REESS emitted gases
[cir] Water exposure during vehicle washing and driving through 10-
centimeter (cm) deep water on roadway.
[cir] Thermal shock and cycling (-40 [deg]C to 60 [deg]C) * \21\
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    \21\ The asterisk notes that this NPRM is not proposing to adopt 
the GTR No. 20 requirement.
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[cir] Resistance to short duration external gasoline pool fire *
[cir] Vibration environment during normal vehicle operations *

 Warning systems for REESS safe operation in case of:

[cir] Low energy content in REESS * \22\
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    \22\ This NPRM does not propose to require a warning for low 
energy in REESS. There is no such warning requirement for 
conventional fuel vehicles in the event of low-fuel, yet all 
conventional fuel vehicles have a low fuel indicator because it is a 
consumer convenience feature. The agency expects that, similarly, a 
low energy in REESS indicator will be voluntarily provided in all 
electric-powered vehicles.
---------------------------------------------------------------------------

[cir] REESS control operational failure
[cir] Thermal runaway propagation due to single cell short circuit in 
REESS
[cir] Thermal event in REESS
 Installation (location) of REESS on the vehicle \23\
---------------------------------------------------------------------------

    \23\ This requirement is intended for countries with type 
approval systems where a generic REESS can be approved separate from 
the vehicle. A vehicle with a pre-approved REESS that complies with 
the REESS installation requirement would not have to undergo post-
crash safety assessment for approval. This installation requirement 
would not apply in the U.S. with a self-certification system.

    This NPRM proposes to complete the alignment of FMVSS No. 305 with 
GTR No. 20 by extending the standard's electrical safety requirements 
to heavy vehicles. This NPRM also proposes to adopt the above 
requirements for the REESS to light and heavy vehicles, except as noted 
by an asterisk, because requirements for thermal shock and cycling, 
resistance to short duration external pool fire, and vibration 
environment are already included under United States Hazardous 
Materials Regulations (HMR), 49 CFR parts 171 to 180, in accordance 
with the international lithium battery transportation requirements of 
UN 38.3, ``Transport of dangerous goods: Manual of tests and 
criteria.'' To avoid redundancy, NHTSA is not proposing adding these 
requirements into FMVSS No. 305a. NHTSA explains the bases for the 
proposals and, for provisions not proposed, the reasons the agency has 
not proposed them in this NPRM.
    GTR No. 20 includes post-crash requirements but does not specify 
the crash tests for post-crash evaluation. Instead, the GTR allows 
contracting parties to apply the crash tests in their regulations. 
Further, the GTR allows contracting parties to permit regulated 
entities to comply with post-crash requirements without conducting 
vehicle crash tests. In place of crash tests, a contracting party may 
specify tests for ``mechanical integrity'' and ``mechanical shock'' of 
the REESS. The mechanical integrity test uses a quasi-static load of 
100 kN on the REESS to evaluate the safety performance of the REESS 
under contact loads that may occur during vehicle crash. The mechanical 
shock test accelerates the REESS on a sled system to evaluate the 
safety performance of the REESS and the integrity of the REESS mounting 
structures to the vehicle under inertial loads that may occur. NHTSA 
discusses its assessment of the component level mechanical integrity 
and mechanical shock test procedures and requests comment on these 
issues later in this NPRM.

III. Proposals Based on GTR No. 20

a. Expanding Applicability of FMVSS No. 305a to Heavy Vehicles

    NHTSA proposes to harmonize the application of FMVSS No. 305a with 
GTR No. 20. Currently, FMVSS No. 305 applies to electric-powered 
vehicles with a GVWR less than or equal to 4,536 kg (10,000 lb); it 
does not apply to electric vehicles with a GVWR greater than 4,536 kg 
(10,000 lb). GTR No. 20 applies to both light and heavy electric 
vehicles. NHTSA proposes to apply FMVSS No. 305a to both light and 
heavy electric vehicles. The fundamentals for protecting against an 
electrical shock for light vehicles are the same as for heavy vehicles. 
A failure of a high voltage system may cause injurious electric shock 
to the human body.
    Specifically, NHTSA proposes to apply FMVSS No. 305a to all 
passenger cars, multipurpose passenger vehicles, trucks, and buses, 
regardless of their GVWR, that use electrical propulsion components 
with working voltages greater than or equal to 60 VDC or 30 VAC, and 
whose speed attainable over a distance of 1.6 kilometers (km) (1 mile) 
on a paved level surface is more than 40 km/h (25 miles per hour 
(mph)).\24\ The NPRM proposes to carry over the current requirements 
for light vehicles in FMVSS No. 305 to FMVSS No. 305a, except some 
provisions as enhanced by this NPRM if adopted by a final rule. To sum, 
light vehicles would have to meet the requirements for normal vehicle 
operations and the requirements proposed in this NPRM for the REESS. 
Further, they would have to meet requirements for post-crash 
protections following a crash test. Under proposed FMVSS No. 305a, 
heavy school buses would have to meet the requirements for normal 
vehicle operations and for the REESS, and, following a specific crash 
test, requirements for post-crash protections. The agency is not 
adopting the provision in GTR No. 20 that conducts mechanical integrity 
and mechanical shock tests (component-level) for light vehicles and for 
heavy school buses. NHTSA believes that post-crash safety is better 
evaluated at a system level in a crash test than in component-level 
tests. Currently there are crash tests for light vehicles and school 
buses, thus, NHTSA proposes to conduct post-crash safety after the 
specified crash tests.
---------------------------------------------------------------------------

    \24\ Current FMVSS No. 305 does not apply to these vehicles that 
travel under 40 km/h (25 mph).
---------------------------------------------------------------------------

    Heavy vehicles other than heavy school buses would be subject to 
the requirements for normal vehicle operations described above and the 
requirements for the REESS. They would not be subject to crash testing 
requirements because the agency does not know of a crash test that 
would be appropriate for the vehicles at this time. However, while 
NHTSA does not have a sufficient basis to proceed currently with 
dynamic or quasi-static requirements for heavy vehicles other than 
school buses, this NPRM requests comment on this issue. NHTSA is 
interested in the merits of component-level tests that are 
representative of impact loads in heavy vehicle crashes and the 
appropriateness of applying the tests to different weight classes of 
heavy vehicles. Even in the absence of post-crash testing requirements, 
NHTSA tentatively concludes that meeting requirements for normal 
vehicle operations and for the REESS, as a starting point, will enhance 
the safety of these heavy electric vehicles.
1. Heavy School Buses
    NHTSA proposes to distinguish heavy school buses from other types 
of heavy vehicles and subject them to crash testing because the school 
vehicles will be carrying children. This NPRM proposes to assess the 
post-crash safety of heavy school buses (school buses with a GVWR 
greater than 4,536 kg (10,000 lb)) in a dynamic moving contoured 
barrier test. This proposal would be consistent with current school bus 
safety standards. FMVSS No. 301, ``Fuel system integrity,'' and FMVSS 
No. 303, ``Fuel system integrity of compressed natural gas vehicles,'' 
require heavy school buses using

[[Page 26709]]

conventional fuel or compressed natural gas for propulsion, 
respectively, to maintain fuel system integrity in a crash test where a 
moving contoured barrier traveling at any speed up to 48 km/h (30 mph) 
impacts the school bus at any point and angle. These standards set this 
high level of safety for heavy school buses even though FMVSS Nos. 301 
and 303 do not apply to other types of heavy vehicles.
    NHTSA recognizes that FMVSS No. 305 currently does not apply to nor 
has a crash test requirement for heavy school buses. When FMVSS No. 305 
was first promulgated in September 2000, NHTSA decided not to apply 
proposed FMVSS No. 305 to heavy school buses. NHTSA made this decision 
after agreeing with commenters that applying the standard to the 
vehicles at that time could have substantial effect, in terms of cost 
and weight, on heavy school buses and potentially restrict further 
development.\25\ The prevailing technology at that time was a series of 
conventional lead-acid batteries as the energy source for propulsion. 
Since the 1990s and early 2000s, battery technology and electric 
powertrains have evolved to include nickel metal hydride and lithium-
ion batteries for electric vehicles. The weight and cost concerns 
raised for electric school buses in 2000 are no longer obstacles with 
current lithium-ion battery technologies because of their high energy 
density and their widespread use. Several school bus manufacturers are 
currently manufacturing and offering for sale heavy school buses with 
high voltage electric propulsion systems. Given the development of the 
technology and practicability of designing and producing heavy electric 
school buses, NHTSA tentatively concludes it is appropriate to adopt 
requirements to ensure post-crash safety of heavy electric school buses 
and maintain the current high level of safety of heavy school buses.
---------------------------------------------------------------------------

    \25\ Final rule, 65 FR 57980, September 27, 2000.
---------------------------------------------------------------------------

    NHTSA is proposing to include in FMVSS No. 305a a requirement that 
heavy school buses with high voltage electric propulsion systems meet 
the requirements for normal vehicle operations (assessed prior to a 
crash test) and the proposed post-crash electrical safety requirements 
when impacted by the moving contoured barrier specified in FMVSS No. 
301. The crash test requirement would align FMVSS No. 305a's 
requirements for heavy school buses with those of FMVSS Nos. 301 and 
303. Due to the number of electric school bus manufacturers and sales 
since 2000, NHTSA tentatively concludes that meeting the proposed 
standard would have no substantial effect on cost and weight due to 
widespread use of lithium-ion battery and conformance to the proposed 
post-crash safety requirements.\26\
---------------------------------------------------------------------------

    \26\ Currently, all major school bus manufacturers (Blue Bird, 
IC Bus, Thomas Built) are offering large and small electric school 
buses (see AFDC-electric school bus) and many school districts have 
introduced electric powered school buses in their fleets. As of June 
2023, there are 2,277 electric school buses that are either on 
order, delivered or operating in the U.S. In total, there are now 
5,982 committed electric school buses in the U.S. https://
www.wri.org/insights/where-electric-school-buses-
us#:~:text=As%20of%20June%202023%2C%20there,more%20buses%20since%20Ju
ne%202022.
---------------------------------------------------------------------------

2. Heavy Vehicles Other Than School Buses
    There are currently no heavy vehicle crash tests in FMVSS. Heavy 
vehicles are typically made to order with different configurations \27\ 
based on the operational needs of the purchaser and are produced in low 
volume. Conducting crash tests of various design configurations from a 
small volume of representative vehicles would be cost prohibitive. 
There could also be practicability constraints for conducting crash 
tests on higher weight classes of heavy vehicles.
---------------------------------------------------------------------------

    \27\ These differences include the number of fuel containers and 
battery packs and the location and attachment of fuel lines and fuel 
containers.
---------------------------------------------------------------------------

    In this NPRM, NHTSA has proposed requirements to ensure post-crash 
safety using full vehicle crash tests for light vehicles and heavy 
school buses. Such full vehicle crash tests evaluate post-crash safety 
at a system level, so NHTSA is not considering component-level tests of 
the REESS for those vehicles. However, since there are no full vehicle 
crash tests currently in FMVSSs for heavy vehicles (other than heavy 
school buses), NHTSA seeks comment on considerations for component-
level tests (other than the mechanical integrity and mechanical shock 
tests in GTR No. 20) that are representative of impact loads in heavy 
vehicle crashes and that can be applied to different weight classes of 
heavy vehicles.
i. Request for Comment; Mechanical Integrity Test
    There are currently no crash tests specified in the FMVSSs \28\ for 
evaluating the integrity of the fuel system or propulsion system of 
heavy vehicles other than heavy school buses. GTR No. 20 provides an 
option for evaluating post-crash safety of light vehicles by way of a 
mechanical integrity test (crush test) of the REESS as an item of 
vehicle equipment, instead of a full vehicle crash test as in FMVSS No. 
305. The loads in the mechanical integrity requirements in the GTR No. 
20 were derived from REESS contact loads measured in light passenger 
vehicle crash tests per UN Regulations ECE R. No. 12, ``Uniform 
provisions concerning the approval of vehicles with regard to the 
protection of the driver against the steering mechanism in the event of 
impact,'' ECE R.94, ``Uniform provisions concerning the approval of 
vehicles with regard to the protection of the occupants in the event of 
a frontal collision,'' and ECE R.95, ``Uniform provisions concerning 
the approval of vehicles with regard to the protection of occupants in 
the event of a lateral collision,'' using electric and hybrid-electric 
vehicles available on the market.
---------------------------------------------------------------------------

    \28\ FMVSS No. 301, ``Fuel system integrity,'' and FMVSS No. 
303, ``Fuel system integrity of compressed natural gas vehicles,'' 
only applies to light vehicles and to heavy school buses.
---------------------------------------------------------------------------

    In the mechanical integrity test, a quasi-static load is applied to 
the charged REESS \29\ along with any subsystem components (including 
crush protection systems specified by the manufacturer) along the 
longitudinal axis of the vehicle (along the direction of vehicle 
travel) or the lateral axis (perpendicular to the longitudinal axis). A 
peak load of 100 kN is applied within 3 minutes and maintained for at 
least 100 milliseconds. During the integrity test, the REESS is 
required to have no evidence of electrolyte leakage, fire, or 
explosion. The REESS is required to have electric isolation of at least 
100 ohms/volt or provide protection level IPXXB against direct contact 
of high voltage sources.\30\
---------------------------------------------------------------------------

    \29\ The REESS is charged to 95 percent state-of-charge for 
REESS designed to be externally charged and charged to no less than 
90 percent of state-of-charge for REESS designed to be charged only 
by an energy source on the vehicle.
    \30\ IPXXB and IPXXD ``protection levels'' refer to the ability 
of the physical barriers to prevent entrance of a probe into the 
enclosure, to ensure no direct contact with high voltage sources. 
``IPXXB'' is a probe representing a small human finger. ``IPXXD'' is 
a slender wire probe. Protection degrees IPXXD and IPXXB are 
International Electrotechnical Commission specifications for 
protection from direct contact of high voltage sources.
---------------------------------------------------------------------------

    Because there are no full vehicle crash tests currently in FMVSSs 
for heavy vehicles (other than heavy school buses), NHTSA seeks comment 
on a mechanical integrity test for REESS on heavy vehicles to evaluate 
post-crash safety at a component-level. As noted above, the current 
quasi-static loads of the integrity test specified in GTR No. 20 are 
specific to light vehicles. NHTSA seeks comment on the parameters for a

[[Page 26710]]

possible quasi-static crush test for the REESS on heavy vehicles.\31\ 
The agency requests feedback on the merits of the integrity test in 
assessing post-crash safety for heavy vehicle REESS. NHTSA seeks 
comment on the practicability of such a test and on the specifics of 
subsystem components that should be included with the REESS while 
conducting the crush test. NHTSA requests that commenters provide data 
to substantiate their assertions.
---------------------------------------------------------------------------

    \31\ NHTSA's research evaluated the crush resistance of REESS 
using a displacement-based loading method. See Ford Safety 
Performance of Rechargeable Energy Storage Systems, Appendix A, DOT 
HS 812 756, July 2019. https://rosap.ntl.bts.gov/view/dot/41840.
---------------------------------------------------------------------------

ii. Request for Comment; Mechanical Shock Test
    NHTSA seeks comment to inform our research on a mechanical shock 
test for REESS on heavy vehicles to evaluate post-crash safety at a 
component level. The aim of the mechanical shock requirement in GTR No. 
20 is to verify the safety performance of the REESS under inertial 
loads which may occur during an impact. The requirement evaluates 
specifically the performance of the REESS mountings and fixtures to the 
vehicle.
    The mechanical shock test is conducted with the REESS along with 
any subsystem components installed on a sled system using the mounting 
structures that are used for installing the REESS to the vehicle. The 
REESS is decelerated or accelerated with an acceleration profile within 
the acceleration corridor in Figure 1 and in accordance with 
acceleration magnitudes in Table 1 through Table 3 for different 
vehicle GVWRs. The test concludes with an observation period of one 
hour at the ambient temperature conditions of the test environment.
[GRAPHIC] [TIFF OMITTED] TP15AP24.044

Figure 1--Generic Description of Test Pulses--Mechanical Shock Test

   Table 1--Mechanical Shock Test--Acceleration Values for Vehicles With a GVWR Less Than or Equal to 3,500 kg
                                                   (7,716 lbs)
----------------------------------------------------------------------------------------------------------------
                                                                                         Acceleration (g)
                              Point                                  Time (ms)   -------------------------------
                                                                                   Longitudinal     Transverse
----------------------------------------------------------------------------------------------------------------
A...............................................................              20               0               0
B...............................................................              50              20               8
C...............................................................              65              20               8
D...............................................................             100               0               0
E...............................................................               0              10             4.5
F...............................................................              50              28              15
G...............................................................              80              28              15
H...............................................................             120               0               0
----------------------------------------------------------------------------------------------------------------


 Table 2--Mechanical Shock Test--Acceleration Values for Vehicles With a GVWR Greater Than 3,500 kg (7,716 lbs)
                                and Less Than or Equal to 12,000 kg (26,455 lbs)
----------------------------------------------------------------------------------------------------------------
                                                                                         Acceleration (g)
                              Point                                  Time (ms)   -------------------------------
                                                                                   Longitudinal     Transverse
----------------------------------------------------------------------------------------------------------------
A...............................................................              20               0               0
B...............................................................              50              10               5
C...............................................................              65              10               5
D...............................................................             100               0               0

[[Page 26711]]

 
E...............................................................               0               5             2.5
F...............................................................              50              17              10
G...............................................................              80              17              10
H...............................................................             120               0               0
----------------------------------------------------------------------------------------------------------------


Table 3--Mechanical Shock Test--Acceleration Values for Vehicles With a GVWR Greater Than 12,000 kg (26,455 lbs)
----------------------------------------------------------------------------------------------------------------
                                                                                         Acceleration (g)
                              Point                                  Time (ms)   -------------------------------
                                                                                   Longitudinal     Transverse
----------------------------------------------------------------------------------------------------------------
A...............................................................              20               0               0
B...............................................................              50             6.6               5
C...............................................................              65             6.6               5
D...............................................................             100               0               0
E...............................................................               0               4             2.5
F...............................................................              50              12              10
G...............................................................              80              12              10
H...............................................................             120               0               0
----------------------------------------------------------------------------------------------------------------

    During the mechanical shock test, the REESS is required to have no 
evidence of electrolyte leakage, fire, or explosion. The REESS is 
required to have electric isolation of at least 100 ohms/volt or have 
protection degree IPXXB.
    Since there are no full vehicle crash tests currently in FMVSSs for 
heavy vehicles (other than heavy school buses) to evaluate post-crash 
safety at a system level, NHTSA seeks comment to inform possible future 
research on a mechanical shock test for REESS on heavy vehicles to 
evaluate post-crash safety at a component level. Among other matters, 
NHTSA requests comment on the following apparent limitations of the GTR 
test. The mechanical shock test in GTR No. 20 aims primarily at 
evaluating the safety performance of the REESS mounting fixture, which 
does not appear to address a safety need presently observed in the 
field.\32\ Furthermore, the accelerations captured in the GTR No. 20 
for the mechanical shock requirement may be too low, according to a 
technical study performed by the Transportation Research 
Laboratory.\33\ The aim of the technical study was to review the 
appropriateness of the crash pulses used in current European 
regulations. This study determined that the crash pulse requirements in 
a number of the EU regulations (including R67, R100, and R110) are not 
representative of current vehicles. (These are among the reasons NHTSA 
is not proposing the mechanical shock test in GTR No. 20 for heavy 
vehicles in this NPRM.)
---------------------------------------------------------------------------

    \32\ Under the Vehicle Safety Act, the FMVSSs must, among other 
things, be practicable, meet the need for motor vehicle safety, and 
be stated in objective terms. (49 U.S.C. 30111(a).)
    \33\ European Commission, Directorate-General for Internal 
Market, Industry, Entrepreneurship and SMEs, Edwards, M., Hylands, 
N., Grubor, D., et al., Technical study to review the 
appropriateness of crash pulses used in current EU legislation: 
final report, Section 4.4, Publications Office, 2021, https://data.europa.eu/doi/10.2873/58935.
---------------------------------------------------------------------------

    NHTSA seeks comment on the relevance of the mechanical shock test 
for heavy vehicles. NHTSA seeks comment on how the mechanical shock 
test would be performed on heavy vehicle REESSs, the appropriate 
accelerations levels that would be representative of acceleration 
levels observed in the field or in crash tests, and appropriate 
requirements which the REESS would need to meet in a mechanical shock 
test.
    NHTSA seeks comment on the best approach or test method for 
evaluating post-crash safety for electric vehicles with a GVWR greater 
than 4,536 kg (10,000 lb). Specifically, NHTSA seeks comment and 
recommendations on other applicable safety tests and corresponding 
objective performance criteria to evaluate the propulsion system crash 
safety performance of vehicles with a GVWR greater than 4,536 kg 
(10,000 lb). NHTSA seeks comment on whether the moving contoured 
barrier crash test proposed for heavy school buses in the above section 
in this preamble can or should be applied to all heavy vehicles.

b. General Specifications Relating To Crash Testing

    This NPRM proposes several general provisions from GTR No. 20 that 
would apply to various testing and performance requirements. NHTSA 
highlights the following proposals below. These provisions pertain to 
light vehicles and heavy school buses subject to the crash testing 
requirements of proposed FMVSS No. 305a.
1. Low Energy Option for Capacitors
    Currently, FMVSS No. 305 S5.3 requires that vehicles meet one of 
the following three criteria post-crash: electrical isolation; absence 
of high voltage; or physical barrier protection. This NPRM proposes a 
low energy option for capacitors in the electric powertrain in FMVSS 
No. 305a.
    Capacitors store electrical energy and may be connected directly to 
the chassis in some electric power trains. In fuel cell electric 
vehicles (FCEVs), the high-voltage systems may contain capacitors that 
are connected to high voltage buses and are not electrically isolated. 
Such capacitors may be high voltage sources post-crash (because a 
charged capacitor may not discharge quickly) and may not be able to 
comply with post-crash electrical safety requirements using the direct 
and indirect contact protection option or the electrical isolation. 
However, capacitors may not pose a safety hazard when contacted, even 
though they may be high voltage sources post-crash, because they are 
low energy high voltage sources.

[[Page 26712]]

    NHTSA has previously considered this issue. In a 2007 NPRM 
responding to petitions for rulemaking from what were then the Alliance 
of Automobile Manufacturers (Alliance) and the Association of 
International Automobile Manufacturers (AIAM),\34\ NHTSA sought 
comments regarding a request of the petitioners to include 0.2 Joule 
(J) as an appropriate low energy threshold for electrical safety 
compliance post-crash for high voltage sources.\35\ The petitioners 
believed that the low energy option was non-harmful, and argued in 
their subsequent comments to the NPRM \36\ that the option is necessary 
due to the presence of x- and y-capacitors in the powertrain of fuel 
cell vehicles. After evaluating the comments, NHTSA ultimately 
disagreed with the petitioners and decided against a low energy option 
for post-crash electrical safety because the agency was not convinced 
that a low energy option was needed and had concerns about the possible 
disparity between the level of safety provided by 0.2 J of energy and 
the electrical isolation requirement.\37\ At that time a safety need 
for a low energy option was not yet clear and the agency expressed 
concerns regarding the practicality of measuring the residual energy in 
a crash test environment.
---------------------------------------------------------------------------

    \34\ In January 2020, the two industry associations merged to 
form the Alliance for Automotive Innovation (generally referred to 
as the Auto Innovators).
    \35\ 72 FR 57260, October 9, 2007.
    \36\ NHTSA-2007-28517-0004.
    \37\ Final rule, 75 FR 33515, 33519; June 14, 2010.
---------------------------------------------------------------------------

    NHTSA is reconsidering this issue in this NPRM. GTR No. 20 contains 
a detailed analysis of the 0.2 Joules energy limit for the low energy 
post-crash electrical safety compliance option. While the 2007 NPRM 
considered a low energy post-crash electrical safety compliance option 
for any high voltage source in the powertrain, GTR No. 20 only provides 
this option to capacitors in the powertrain.
    NHTSA conducted an analysis using human body resistance charts, 
long and short duration capacitance discharge pulse profiles, and the 
graphs of physiological effects of AC and DC body current by duration 
of exposure from two International Electrotechnical Commission (IEC) 
technical publications,\38\ to determine safe energy levels for the 
human body. NHTSA has submitted a technical memorandum to the docket 
for this NPRM that provides details and results of the agency's 
analysis.
---------------------------------------------------------------------------

    \38\ IEC 60479-1 and 60479-2 Effects of Current on Human Beings 
and Livestock--Part 1: General Aspects, Part 2: Special Aspects, 
2005-07, Reference Nos. CEI/IEC/TS 60479-1:2018 and CEI/IEC/TS 
60479-2:2019. https://webstore.iec.ch/publication/62980; https://webstore.iec.ch/publication/63392 (last accessed September 26, 
2023).
---------------------------------------------------------------------------

    Based on the analysis results, NHTSA tentatively concludes that a 
post-crash electrical safety compliance option for capacitors based on 
an electrical energy of 0.2 Joules or less provides adequate safety 
from electrical shock and long-term harmful effects on the human body. 
Providing this post-crash compliance option would allow for practicable 
powertrain designs for battery electric and fuel cell vehicles without 
any reduction in safety. Automotive high-voltage systems typically 
utilize a number of capacitors connected to high voltage buses, and it 
is not always practical to discharge every capacitor post-crash. NHTSA 
tentatively believes that by providing this compliance option for a 
safe energy limit, vehicle manufacturers would have the flexibility to 
design products that assure safety. NHTSA seeks comments on the 
parameters (human body resistance, discharge profiles) used in the 
analysis and the analysis method.
2. Assessing Fire or Explosion in Vehicle Post-Crash Test
    After a real-world crash, passengers within the vehicle need time 
to safely egress from the vehicle or be rescued by first responders. 
During this time, passengers should not be exposed to hazards such as 
fire or explosion of the REESS, which may hinder their egress or 
rescue.
    GTR No. 20 requires that for a period of one hour after a crash 
test, there shall be no evidence of fire or explosion of the REESS. 
However, such a requirement is not currently in FMVSS No. 305. In 
accordance with GTR No. 20, NHTSA proposes to include in FMVSS No. 305a 
a requirement that there be no evidence of fire or explosion for the 
duration of one hour after the crash test for heavy school buses, and 
for the duration of one hour after each crash test and subsequent 
quasi-static rollover test for light vehicles. The assessment of fire 
or explosion would be verified by inspection without removal of the 
REESS or any parts of the vehicle.
3. Assessing Post-Crash Voltage Measurements
    This NPRM proposes to clear up a source of ambiguity in FMVSS No. 
305. FMVSS No. 305 requires that the post-crash voltage measurements be 
made at least 5 seconds after the vehicle comes to rest. However, at 
times it is not entirely clear when the vehicle comes to rest because 
there is always some vibration and slight vehicle motion post-crash. 
For consistency with the GTR No. 20 test procedure, NHTSA proposes that 
the voltage measurements in FMVSS No. 305a would be made between 10 
seconds and 60 seconds after the impact. The agency tentatively 
believes that 10 seconds after impact is sufficient time for voltage 
measurement and 60 seconds after impact is early enough that any high 
voltage arcing would be detected. NHTSA seeks comment on this approach.
4. Electrolyte Spillage Versus Leakage
    Currently, FMVSS No. 305 S5.1 addresses ``electrolyte spillage from 
propulsion batteries.'' The standard specifies that following a crash 
test, not more than 5.0 liters of electrolyte from propulsion batteries 
shall spill outside the passenger compartment, and that no visible 
trace of electrolyte shall spill into the passenger compartment. NHTSA 
proposes to use terms related to ``leakage'' instead of spillage. When 
the electrolyte spillage \39\ requirement was originally adopted in 
2000, EV propulsion batteries were envisioned to be a series of lead-
acid batteries. Lead-acid batteries at the time had large quantities of 
liquid electrolyte that could spill out of the battery if the battery 
structure were compromised in a crash. At that time, it was appropriate 
to eliminate the term ``leakage'' due to its synonymity to 
``spillage,'' to avoid questions of whether different meanings were 
intended by the different words.
---------------------------------------------------------------------------

    \39\ Per Section B, ``S5.1 Electrolyte Spillage from Propulsion 
Batteries,'' NHTSA stated in 65 FR 57980 that ``leakage'' is 
synonymous for ``spillage.'' Both words indicate the escape of 
electrolyte from the battery.
---------------------------------------------------------------------------

    Current EV propulsion batteries, however, are lithium-ion 
batteries. The cells of lithium-ion batteries have small quantity of 
electrolyte that could leak out of the battery casing rather than 
spill. Thus, NHTSA proposes to use the term ``electrolyte leakage,'' 
which is more relevant than ``electrolyte spillage'' for these 
batteries.
    NHTSA seeks comment on the inclusion of a post-crash electrolyte 
leakage requirement in FMVSS No. 305a and the necessity and relevance 
of such a requirement for current EVs. Specifically, NHTSA seeks 
comment on whether this requirement is still relevant given today's 
propulsion battery technologies and if it is still necessary based on 
the safety incidents observed in the field or in crash tests. NHTSA 
seeks comment on whether a 5-liter maximum amount of electrolyte 
permitted to be leaked is still relevant and requests commenters to 
provide data based on safety incidents observed in the field or in 
crash tests to

[[Page 26713]]

substantiate their assertions.\40\ NHTSA seeks comment on and 
recommendations regarding electrolyte leakage detection methods and how 
these detection methods can discern between the presence of electrolyte 
and the presence of other liquids such as coolant.
---------------------------------------------------------------------------

    \40\ GTR No. 20 requires that the electrolyte leaking from the 
REESS during and after the crash test is no more than 7 percent by 
volume of the REESS electrolyte. However, there is no practical way 
of measuring the quantity by volume of the electrolyte in the REESS.
---------------------------------------------------------------------------

c. REESS Requirements Applicable to All Vehicles

    This section of the NPRM addresses REESS safety performance 
requirements during normal vehicle operation. The REESS requirements 
would apply to all vehicles subject to FMVSS No. 305a.
Introduction
    Currently, FMVSS No. 305 does not have any requirements for the 
safe operation of the REESS and for mitigating risks of fire and other 
safety risks associated with it. This NPRM's proposed requirements 
would protect the REESS against external fault inputs, ensure the REESS 
operations are within the manufacturer-specified functional range, 
provide protection from thermal propagation in the event of single-cell 
thermal runaway (SCTR) due to an internal short-circuit, provide a 
warning if there is a thermal event within the REESS or a malfunction 
of vehicle controls that manage REESS safe operation, and ensure safe 
REESS operation during and after water exposure.
    While REESS is a general term to represent any rechargeable 
electrical energy storage system, currently all electric powered 
vehicles use REESS with lithium-ion chemistry. Therefore, the current 
safety hazards associated with REESS identified in literature and in 
the field are those specific to lithium-ion chemistry REESS. However, 
the proposed requirements in this NPRM will apply regardless of REESS 
chemistry.
    REESSs are designed and manufactured to operate safely within a 
range of operating parameters, including temperature ranges, charge 
levels, and current levels. If the REESS is subjected to fault 
conditions outside these operating ranges such as overcharge, over-
discharge, overcurrent, over-temperature, external short-circuit, or 
low temperature, these conditions can result in damage to the cells. 
Cell damage increases the risk of hazardous conditions such as 
electrolyte leakage, reduced electrical isolation, and fire in the 
REESS (thermal runaway). Manufacturers include controls in electric 
vehicles to manage REESS operation to ensure they stay within the 
specified safe operating range, thereby mitigating damage to the REESS. 
The system that monitors and controls the REESS is referred to as the 
battery management system (BMS). NHTSA proposes requirements to assure 
that the BMS has controls that protect the REESS against these faults 
by, e.g., stopping the vehicle from charging to prevent overcharge.
Performance Criteria For Normal Vehicle Operations--General
    The performance criteria specified in GTR No. 20 for each of the 
vehicle control performance tests specify no evidence of electrolyte 
leakage, rupture (applicable to high voltage REESSs only), venting 
(applicable to REESSs other than open-type traction batteries \41\), 
fire, or explosion. For high voltage REESSs, the electrical isolation 
is required to be greater than or equal to 100 ohms per volt, for a DC 
high voltage source. This NPRM proposes the same performance criteria 
to protect the REESS against external faults, such as a fault in an 
external charger that could result in the charger supplying greater 
current than requested by the vehicle and/or charging the REESS beyond 
full state of charge.\42\
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    \41\ Open-type traction batteries are a type of battery which 
are filled with liquid and generate hydrogen gas that is released 
into the atmosphere.
    \42\ The control pilot pin of the charger communicates with the 
vehicle during charging. Based on the state of charge (SOC), the 
vehicle requests a certain level of current and the vehicle charger 
provides that level. Other external faults could arise when 
attempting to drive the vehicle beyond the lowest safe operating SOC 
of the REESS (over-discharge of the REESS), driving fast up a steep 
hill for a long period of time that could cause the REESS to heat 
beyond its highest safe operating temperature, and charging a REESS 
at very cold temperatures that could cause lithium plating.
---------------------------------------------------------------------------

    Under proposed FMVSS No. 305a, the evidence of electrolyte leakage, 
venting,\43\ or rupture is verified by visual inspection without 
disassembly of any part of the vehicle. Visible smoke during and after 
the test, and/or the presence of soot and/or electrolyte residue in 
post-test visual inspection are indicators of venting and electrolyte 
leakage. The overcharge, over-discharge, overcurrent, over-temperature, 
and external short-circuit test procedures specify that the agency 
would perform a standard cycle after completing exposure to each of the 
external faults, provided that the vehicle permits charging and 
discharging at that time. A standard cycle, as specified in GTR No. 20 
and proposed FMVSS No. 305a, consists of a standard discharge and 
followed by a standard charge. If the vehicle is operable after 
exposure to the external fault, running the standard cycle after 
exposure to the external fault condition--while observing the vehicle 
for one hour for evidence of electrolyte leakage, rupture, venting, 
fire, or explosion, followed by voltage measurements for determining 
electrical isolation--would ensure that continuing operating the 
vehicle would not result in safety hazards.
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    \43\ NHTSA elaborates on the proposed venting requirement at the 
end of this section.
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    The vehicle might not permit charging and discharging after 
detecting a dangerous condition; NHTSA considers this a safety feature 
and that such a test outcome would not amount to an apparent 
noncompliance. The inability to perform a standard cycle after exposure 
to the external fault does not terminate the test. If the vehicle does 
not permit charging and discharging after exposure to an external 
fault, then the standard cycle is simply not performed and the test 
proceeds. Specifically, the test ends with the vehicle observed for one 
hour for evidence of electrolyte leakage, rupture, venting, fire, or 
explosion, followed by voltage measurements for determining electrical 
isolation.
    The standard cycle would be conducted with the breakout harness 
connected to the manufacturer-specified location(s) on the traction 
side of the REESS \44\ on the vehicle's electric power train. The REESS 
is charged and discharged using a high voltage battery tester/cycler 
(with appropriate power and voltage ranges) which is connected to the 
vehicle through the breakout harness, as shown in Figure 2 below (for 
illustration purposes only).
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    \44\ The manufacturer is required by proposed FMVSS No. 305a to 
specify the location for connecting the breakout harness and may 
also provide appropriate breakout harnesses for testing the vehicle. 
If the manufacturer does not provide a breakout harness, NHTSA would 
use a generic breakout harness to connect to the traction side of 
the REESS.

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[[Page 26714]]

[GRAPHIC] [TIFF OMITTED] TP15AP24.045

Figure 2--Connection of the Breakout Harness & Laboratory Test 
Equipment to the Vehicle

    NHTSA proposes that the discharge and charge rates for the standard 
cycle would be provided by the vehicle manufacturer. NHTSA proposes 
that, if the discharge rate is not specified by the manufacturer, NHTSA 
would use a discharge rate (C-Rate) of 1C current. A ``nC Rate'' is the 
magnitude of constant current that would charge or discharge the REESS 
in 1/n hour between 0 percent state of charge (SOC) and 100 percent 
SOC. Discharge would continue until automatically terminated by vehicle 
controls at the manufacturer-specified minimum operating SOC of the 
REESS. After discharge, the standard cycle would include a 15-minute 
rest period before the charging procedure commences. If a charge 
procedure is not specified, then a charge rate (i.e., C-Rate) of \1/3\C 
current would be used. Charging is continued until automatically 
terminated by vehicle controls at the manufacturer-specified maximum 
operating SOC of the REESS.
REESS Venting
    Venting is the release of excessive internal pressure from a cell 
or REESS in a manner intended by design to preclude rupture or 
explosion. Venting during normal vehicle use may be associated with (a) 
combustion and/or decomposition of electrolyte, or (b) vaporization of 
the electrolyte. In case of condition (a), the emissions from the cells 
may increase the risk to vehicle occupants if they are exposed to such 
substances. In case of condition (b), the amount of the gases released 
is considered less likely to pose a safety risk to the occupants. 
Venting in the case of condition (a) may result in the release of gases 
and particulates from the REESS, thereby potentially exposing vehicle 
occupants to the emissions (gases and particulate matter).\45\ Hazards 
associated with toxicity, corrosiveness, and flammability of the gases 
emitted from the REESS and associated human health exposure limits vary 
considerably. As noted above, NHTSA proposes to include a provision in 
FMVSS No. 305a to limit the safety risks to vehicle occupants due to 
venting during normal vehicle operations. The provision is based on GTR 
No. 20 requirements described below.
---------------------------------------------------------------------------

    \45\ Gases generated in and vented from lithium-ion (Li-ion) 
batteries typically include carbon dioxide (CO2), carbon 
monoxide (CO), hydrogen (H2), oxygen (O2), 
light C1-C5 hydrocarbons, e.g., methane and 
ethane, and fluorine-containing compounds such as hydrogen fluoride 
(HF) and fluoro-organics, e.g., ethyl-fluoride.
---------------------------------------------------------------------------

    GTR No. 20 specifies that under normal vehicle operation, the 
vehicle occupants are not exposed to any hazardous environment caused 
by venting from the REESS. To avoid human harm that may occur due to 
potential toxic or corrosive emissions, GTR No. 20 specifies that there 
be no venting from the REESS for the following normal vehicle 
operations tests: vibration, thermal shock and cycling, external short 
circuit protection, overcharge protection, over-discharge protection, 
over-temperature protection and overcurrent protection. GTR No. 20 
includes a no-fire requirement in these tests which addresses the issue 
of vented gas flammability. During the development of GTR No. 20, a 
robust and repeatable method to verify the occurrence of

[[Page 26715]]

venting and the potential exposure of vehicle occupants to various 
gases from the venting was sought, but no suitable method was found. 
Visual inspection was found to be the best approach at this time for 
verifying the occurrence of venting for assessing the influence of 
vented gases on vehicle occupants. Therefore, GTR No. 20 specifies that 
evidence of venting in these tests is verified by visual inspection 
(evidence of soot, electrolyte residues) without disassembling any part 
of the REESS.
    NHTSA proposes to use a similar approach in FMVSS No. 305a to 
evaluate the safety risks to vehicle occupants resulting from venting 
from the REESS. The agency acknowledges that research is needed to 
develop a repeatable, reproducible, and practical method to verify the 
occurrence of various vented gases and the potential exposure and harm 
to vehicle occupants. However, NHTSA tentatively concludes that in the 
absence of such a method, the requirement that there must be no fire, 
electrolyte leakage or venting during the tests evaluating vehicle 
controls for safe REESS operation (external short-circuit protection, 
overcharge protection, over-discharge protection, over-temperature, and 
overcurrent protection) would reduce some safety risks to vehicle 
occupants due to venting from the REESS. The evidence of venting in 
these tests would be verified by visual inspection (evidence of soot, 
electrolyte residues) without disassembling any part of the REESS.
    NHTSA also requests comment in an Appendix to this preamble on the 
IWG's continuing work on venting in Phase 2 of the GTR.
1. Vehicle Controls for Safe REESS Operation
    This NPRM proposes the following performance requirements and 
associated test procedures for vehicles to ensure they have controls 
managing safe REESS operations. There are some minor differences 
between the GTR No. 20 test procedures and those proposed in this NPRM 
that are based on the lessons learned from NHTSA's test program. Those 
differences pertain to the ease of conducting the test.\46\
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    \46\ For example, the state of charge of the REESS at the 
beginning of the test differed in some instances from that in GTR 
No. 20 to enable completing the test more readily.
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    NHTSA funded research to validate a collection of test procedures 
that assess safety hazards to electric vehicles while being charged or 
when the REESS exceeds its recommended operational 
limits.47 48 The research independently evaluated, refined, 
and validated vehicle-level test procedures that could be robustly 
applied to a wide range of vehicle technologies and battery 
configurations. Based on the results of NHTSA's research, the agency 
proposes to conduct full vehicle-level tests using a breakout harness 
connected to a battery tester/cycler \49\ to evaluate vehicle controls 
for safe REESS operation, rather than conducting the tests on the REESS 
as a separate component. NHTSA is proposing vehicle-level testing 
because evaluating REESS safe operation at the vehicle level would 
evaluate the entire vehicle system and the associated vehicle controls, 
whereas conducting the tests at the equipment level would not evaluate 
all the relevant vehicle controls or any interaction or interference 
between vehicle controls.
---------------------------------------------------------------------------

    \47\ DC Charging Safety Evaluation Procedure Development, 
Validation, And Assessment, and Preliminary AC Charging Evaluation 
Procedure--DOT HS 812 754 and DOT HS 812 778--July 2019. https://rosap.ntl.bts.gov/view/dot/41933.
    \48\ System-Level RESS Safety and Protection Test Procedure 
Development, Validation, and Assessment--Final Report--DOT HS 812 
782 October 2019 https://rosap.ntl.bts.gov/view/dot/42551.
    \49\ A battery tester/cycler is equipment that can be used for 
charging and discharging REESS and for conducting specialized tests 
on the REESS. An example of a battery tester with hybrid and battery 
electric vehicles is the NHR 9300 battery test system (NHR 9300).
---------------------------------------------------------------------------

    NHTSA evaluated the GTR No. 20 test procedures for feasibility, 
practicability, and objectivity by conducting the test procedures on a 
2019 Chevy Bolt, 2020 Tesla Model 3, and 2020 Nissan Leaf S 
Plus.50 51 52 NHTSA's test program demonstrated the ease of 
conducting tests at a vehicle level using breakout harnesses connected 
to a battery cycler/tester for the external inputs to the REESS without 
having to remove the REESS from the vehicle to conduct component level 
tests. The proposed test procedures for overcharge, over-discharge, 
overcurrent, over-temperature, and external short-circuit tests are 
non-destructive tests intended to evaluate vehicle controls to protect 
the REESS and can be conducted in serial order on the same vehicle.
---------------------------------------------------------------------------

    \50\ NHTSA Test Report on the 2020 Tesla Model 3 Standard Range 
4-Door Sedan can be accessed here: https://downloads.regulations.gov/NHTSA-2021-0029-0003/attachment_2.pdf.
    \51\ NHTSA Test Report on the 2020 Nissan Leaf S Plus (62kWh 
Battery) 5-Door Hatchback can be accessed here: https://downloads.regulations.gov/NHTSA-2021-0029-0002/attachment_2.pdf.
    \52\ NHTSA Test Report on the 2019 Chevy Bolt can be accessed 
here: https://downloads.regulations.gov/NHTSA-2021-0029-0001/attachment_2.pdf.
---------------------------------------------------------------------------

i. Overcharge Protection
    A battery pack experiences an overcharge when a charger forces its 
state of charge (SOC) level to rise above 100 percent. Overcharge of a 
REESS can occur because of a failure of the charging system, such as a 
fault in an external charger, a fault in the vehicle's regenerative 
braking system, a sensor failure, or a voltage reference drift.\53\ 
Overcharge can lead to swelling of an electrochemical cell, lithium 
plating, stability degradation, or over-heating, and ultimately can 
lead to thermal runaway.\54\ Severe events such as fire or explosion 
may occur. Therefore, vehicle controls to ensure the REESS does not get 
overcharged are important for long-term safe operation of the REESS.
---------------------------------------------------------------------------

    \53\ Voltage can drift based on temperature. Higher temperature 
can result in lower voltage.
    \54\ Thermal runaway of a lithium-ion cell in a REESS occurs 
when the thermal stability limit of the cell chemistry is exceeded, 
and the cell releases its energy via an exothermic reaction at an 
uncontrolled rate such that the heat generated is faster than that 
dissipated.
---------------------------------------------------------------------------

    Vehicle level controls or the BMS typically prevent charging when 
the manufacturer-specified maximum operating SOC of the REESS is 
achieved. GTR No. 20 includes a test to evaluate the performance of 
vehicle controls to prevent overcharge of the REESS. NHTSA tentatively 
concludes that GTR No. 20's overcharge test is practical and feasible 
based on the agency's own testing.\55\ NHTSA proposes to include the 
overcharge protection requirement and test procedure in FMVSS No. 305a.
---------------------------------------------------------------------------

    \55\ See Test reports in docket no. NHTSA-2021-0029, available 
at www.regulations.gov. Detailed test procedures are provided in the 
test reports of the 2021 Chevrolet Bolt (NHTSA-2021-0029-0001), 2020 
Nissan Leaf (NHTSA-2021-0029-0002), and the 2020 Tesla Model 3 
(NHTSA-2021-0029-0003).
---------------------------------------------------------------------------

    The proposed overcharge test would be performed on a complete 
vehicle as follows. The test is conducted with the REESS initially set 
at 90 to 95 percent SOC \56\ and at ambient temperatures between 10 
[deg]C and 30 [deg]C. The breakout harness is attached on the traction 
side of the REESS at the vehicle manufacturer's recommended location(s) 
and attachment point(s), and the battery tester/cycler is connected to 
the breakout harnesses to supply the charge current. Temperature probes 
are connected to the REESS case to monitor changes in the REESS 
temperature. Temperature measurements may also be

[[Page 26716]]

obtained through communication with the REESS control module.\57\
---------------------------------------------------------------------------

    \56\ Ranges in temperature and SOC are provided for this and 
other test procedures for practicability and ease of conducting the 
tests. In the overcharge test, the REESS is initially set at a high 
SOC (90 to 95 percent) to enable fully charging the REESS in a 
shorter period of time.
    \57\ Commercial diagnostic tools or tools supplied by the 
manufacturer may be used to read the Temperature measurements within 
the REESS from the vehicle's Controller Area Network (CAN bus).
---------------------------------------------------------------------------

    The vehicle is turned on and the REESS is charged using the battery 
tester/cycler in accordance with the manufacturer's recommended maximum 
charge current \58\ until one of the following has occurred:
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    \58\ If the manufacturer does not provide an appropriate charge 
current, then a charge rate (i.e., C-Rate) of C/3 current would be 
used.
---------------------------------------------------------------------------

    (a) the REESS overcharge protection control terminates the charge 
current;
    (b) the REESS temperature is 10 [deg]C above its maximum operating 
temperature specified by the manufacturer; \59\ or,
---------------------------------------------------------------------------

    \59\ The manufacturer would specify the procedure for monitoring 
the temperature of the REESS during testing. This could be measured 
by attaching thermocouples to the casing of the REESS or obtained 
from the CAN bus using appropriate tools.
---------------------------------------------------------------------------

    (c) 12 hours have passed since the start of charging the vehicle.
    After the overcharge condition is terminated, a standard cycle is 
performed if possible. The test concludes with a 1-hour observation 
period in which the vehicle is observed for any evidence of electrolyte 
leakage, rupture, venting, fire, or explosion. At the conclusion of the 
post-test observation period, the electrical isolation is determined in 
the same manner as currently in FMVSS No. 305 S7.6 using a voltmeter to 
measure voltages.
ii. Over-Discharge Protection
    Over-discharging a REESS, which means discharging it below its 
lowest state of charge specified by the manufacturer, can lead to 
undesirable aging, electrolyte leakage, swelling, solid electrolyte 
interphase (SEI) decomposition, internal short-circuit, and damaged 
cell stability and safety on subsequent recharges. Even though the 
initial over-discharge response of lithium-ion cells generally appears 
benign, it can cause damage to cell electrodes that can compromise cell 
stability and safety on subsequent recharge. Subsequent charging of an 
over-discharged REESS may lead to fire or explosion.
    Vehicle controls or the BMS typically prevent over-discharging when 
the manufacturer specified minimum operating SOC of the REESS is 
achieved. GTR No. 20 includes a test to evaluate the performance of 
vehicle controls to prevent over-discharge of the REESS. NHTSA 
tentatively concludes that GTR No. 20's over-discharge test is 
practical and feasible based on the agency's own testing.\60\ NHTSA 
proposes to include the over-discharge protection requirement and test 
procedure in FMVSS No. 305a.
---------------------------------------------------------------------------

    \60\ See Test reports in Docket No. NHTSA-2021-0029, available 
at www.regulations.gov. Detailed test procedures are provided in the 
test reports of the 2021 Chevrolet Bolt (NHTSA-2021-0029-0001), 2020 
Nissan Leaf (NHTSA-2021-0029-0002), and the 2020 Tesla Model 3 
(NHTSA-2021-0029-0003).
---------------------------------------------------------------------------

    The over-discharge test is performed at ambient temperatures 
between 10 [deg]C and 30 [deg]C on a complete vehicle. The SOC of the 
REESS at the beginning of the test is set at 10 to 15 percent.\61\ For 
a vehicle with on-board energy conversion systems (e.g., internal 
combustion engine, fuel cell, etc.), the fuel supply is set to the 
minimum level \62\ where active driving mode is permitted. Similar to 
the overcharge test, the breakout harness is attached on the traction 
side of the REESS at the vehicle manufacturer's recommended location(s) 
and attachment point(s), and the battery tester/cycler is connected to 
the breakout harness to discharge the REESS.\63\ Temperature probes are 
connected to the REESS case to monitor changes in the REESS 
temperature. Temperature measurements may also be obtained through 
communication with the REESS control module.
---------------------------------------------------------------------------

    \61\ Ranges in temperature and SOC are provided for this and 
other test procedures for practicability and ease of conducting the 
tests. In this case, the test is initiated with the REESS at a low 
SOC (10 to 15 percent) to enable discharging the REESS in a shorter 
period of time.
    \62\ Minimum level of fuel supply needed would be provided by 
the manufacturer.
    \63\ A discharge resistor may also be used for this purpose.
---------------------------------------------------------------------------

    The vehicle is turned on and the REESS is discharged using the 
battery tester/cycler in accordance with the manufacturer's recommended 
discharging rate \64\ under normal operating conditions until one of 
the following has occurred:
---------------------------------------------------------------------------

    \64\ If the manufacturer does not specify a discharge rate, a 
power load of 1kW is used.
---------------------------------------------------------------------------

    (a) vehicle controls terminate the discharge current,
    (b) the temperature gradient of the REESS is less than 4 [deg]C 
\65\ through two hours, or
---------------------------------------------------------------------------

    \65\ Temperature variation of 4 [deg]C indicates stable 
operation of the REESS. As noted earlier, the manufacturer specifies 
the procedure for monitoring the temperature of the REESS during 
testing. This could be measured by attaching thermocouples to the 
casing of the REESS or obtained from the CAN bus using appropriate 
tools.
---------------------------------------------------------------------------

    (c) if the vehicle is discharged to 25 percent of its nominal 
voltage level.
    At the conclusion of the discharge termination, one standard charge 
is performed, followed by one standard discharge. The test concludes 
with a 1-hour observation period in which the vehicle is observed for 
any evidence of electrolyte leakage, rupture, venting, fire, or 
explosion. At the conclusion of the observation period, the electrical 
isolation is determined in a similar manner as that in current FMVSS 
No. 305 S7.6 using a voltmeter to measure voltages.
iii. Overcurrent Protection
    As noted earlier, the vehicle and the charging system communicate 
the level of current needed to charge the REESS. If there is a problem 
in the communication or if the charging system malfunctions, higher 
current may be provided though not requested by the vehicle. During 
direct current (DC) fast-charging, failure of the external charge 
equipment could cause over-current conditions in which the REESS 
receives higher current than it was designed to manage at a given state 
of charge of the REESS. Overcurrent conditions could result in heating 
of the REESS, electrochemical damage to the cells, and a risk of 
thermal runaway.
    GTR No. 20 includes a test to evaluate the performance of vehicle 
controls to protect the REESS from overcurrent conditions. NHTSA 
tentatively concludes that GTR No. 20's overcurrent test is practical 
and feasible based on the agency's own testing.\66\ NHTSA proposes to 
include the overcurrent protection requirement in FMVSS No. 305a. In 
accordance with GTR No. 20, NHTSA proposes to apply the overcurrent 
test to vehicles that have capability of charging by DC external 
electricity supply. The test is unnecessary for vehicles that only 
charge by alternating current (AC) supply because AC charging is slower 
and the inverters for AC charging manage any overcurrent. Also, 
overcurrent issues have not been observed in AC charging.
---------------------------------------------------------------------------

    \66\ See Test reports in docket no. NHTSA-2021-0029, available 
at www.regulations.gov. Detailed test procedures are provided in the 
test reports of the 2021 Chevrolet Bolt (NHTSA-2021-0029-0001), 2020 
Nissan Leaf (NHTSA-2021-0029-0002), and the 2020 Tesla Model 3 
(NHTSA-2021-0029-0003).
---------------------------------------------------------------------------

    The overcurrent test is performed with a complete vehicle. To avoid 
the overcharge protection terminating the over-current condition, the 
SOC of the REESS is set between 40 to 50 percent. The test is conducted 
at ambient temperatures between 10 [deg]C and 30 [deg]C. The breakout 
harness is attached on the traction side of the REESS at the vehicle 
manufacturer's recommended location(s) and attachment point(s), and the 
battery tester/cycler is connected to the breakout harnesses to supply 
the charge current. Temperature probes are connected to the REESS case 
to monitor changes in the REESS temperature.

[[Page 26717]]

Temperature measurements may also be obtained through communication 
with the REESS control module. The vehicle manufacturer specifies the 
highest normal charge current and the over-current level that is 
applied. The battery tester/cycler is programmed to supply an over-
current during charging at the level specified by the manufacturer.
    The vehicle is turned on and the REESS is charged using the battery 
tester/cycler in accordance with manufacturer's recommended charging 
procedure with the highest normal charge current specified by the 
manufacturer.\67\ After charging is initiated, an over-current 
specified by the manufacturer \68\ is supplied above that requested by 
the vehicle. The charge current is increased over the course of 5 
seconds from the highest normal charge current to the over-current 
level. The charge current and the overcurrent supply is continued until 
one of the following has occurred: (a) vehicle over-current protection 
controls terminate the charging, or (b) the temperature gradient of the 
REESS is less than or equal to 4 [deg]C for a two-hour period.
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    \67\ The manufacturer supplied information define the constant 
current level and/or constant voltage level combination to charge 
the REESS. If a charge procedure is not specified, then a charge 
rate (i.e., C-Rate) of C/3 current is used.
    \68\ If the vehicle manufacturer does not supply an appropriate 
over-current level, the battery test/cycler will be programmed to 
initially apply a 10 Ampere over-current. If charging is not 
terminated, the over-current level of 20 amps will be applied. 
Subsequently, the over-current supply is increased in steps of 10 
amperes.
---------------------------------------------------------------------------

    If possible, a standard cycle is performed using the connected 
breakout harness and battery cycler. The test concludes with an 
observation period of one hour in which the vehicle is observed for 
electrolyte leakage, rupture, venting, fire, or explosion. At the 
conclusion of the observation period, the electrical isolation is 
determined in a similar manner as that in current FMVSS No. 305 S7.6, 
using a voltmeter to measure voltages.
iv. Over-Temperature Protection
    While the impacts of over-temperature operation vary by chemistry, 
most battery chemistries can be negatively affected if operation by the 
driver is attempted at high temperatures (per the limits of a specific 
chemistry) or if aggressive operation is attempted at high temperatures 
(high-rate charging or discharging). A temperature imbalance or 
continued operation at elevated temperatures may even lead to thermal 
runaway of cells if appropriate countermeasures, such as de-rating,\69\ 
are not taken.
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    \69\ De-rating is the reduction of a battery's available power 
and is typically due to a state that indicates an undesirable 
condition such as rapidly increasing cell temperature, elevated 
temperatures, or very cold cell temperatures. By temporarily 
reducing a battery's ability to provide and/or absorb power, de-
rating allows the battery to cool down (or at least stop increasing 
in temperature) in situations with elevated temperatures and reduces 
operation when the battery is so cold that certain usage levels 
could cause damage.
---------------------------------------------------------------------------

    Vehicle controls such as thermal management systems or the BMS 
continuously monitor temperature conditions to prevent REESS operation 
at elevated temperatures above the upper temperature boundary for safe 
REESS operations. GTR No. 20 includes a test to evaluate the 
performance of vehicle controls to prevent REESS temperatures exceeding 
the upper temperature boundary for safe REESS operations. NHTSA 
tentatively concludes that GTR No. 20's over-temperature test is 
practical and feasible based on the agency's own testing.\70\ NHTSA 
proposes to include the over-temperature protection requirement and 
test procedure in FMVSS No. 305a, which aligns with GTR No. 20.
---------------------------------------------------------------------------

    \70\ See Test reports in Docket No. NHTSA-2021-0029, available 
at www.regulations.gov. Detailed test procedures are provided in the 
test reports of the 2021 Chevrolet Bolt (NHTSA-2021-0029-0001), 2020 
Nissan Leaf (NHTSA-2021-0029-0002), and the 2020 Tesla Model 3 
(NHTSA-2021-0029-0003).
---------------------------------------------------------------------------

    In the proposed FMVSS No. 305a, the over-temperature test is 
performed on a chassis dynamometer \71\ with a complete vehicle. The 
SOC of the REESS at the beginning of the test is set between 90 to 95 
percent. The test is conducted at ambient temperatures between 10 
[deg]C and 30 [deg]C. For vehicles with on-board energy conversion 
systems (e.g., internal combustion engine, fuel cell, etc.), the fuel 
system must have sufficient supply to allow operation of the energy 
conversion system for about one hour of driving. The cooling system for 
the REESS is disabled (or significantly reduced for a REESS that will 
not operate with the cooling system disabled) per manufacturer-supplied 
information.\72\ For REESSs that will not operate if the cooling system 
is disabled, the maximum amount of coolant is removed to minimize the 
cooling system's operation for the test.
---------------------------------------------------------------------------

    \71\ A chassis dynamometer is a mechanical device that uses one 
or more fixed roller assemblies to simulate different road 
conditions within a controlled environment and is used for a wide 
variety of vehicle testing.
    \72\ Methods for disabling the cooling system may include 
crimping the liquid cooling hose or in the case of a refrigerant 
cooled package, removing the refrigerant fluid. For REESS cooled by 
cabin air, block the cabin air intakes used to provide cooling air 
flow to the REESS.
---------------------------------------------------------------------------

    Temperature probes are connected to the REESS case to monitor 
changes in the REESS temperature. Temperature measurements may also be 
obtained through communication with the REESS control module.
    GTR No. 20 specifies that the vehicle be soaked for at least 6 
hours in a thermally controlled chamber at 45 [deg]C. However, NHTSA's 
testing \73\ demonstrated that the presoaking of the vehicle at 
elevated temperatures does not raise the temperature of the REESS as 
significantly as by driving the vehicle under high acceleration and 
deceleration drive modes. Therefore, to reduce the test time and test 
burden, the agency does not believe it needs to specify presoaking of 
the vehicle.
---------------------------------------------------------------------------

    \73\ System-Level RESS Safety and Protection Test Procedure 
Development, Validation, and Assessment-Final Report. DOT HS 812 782 
October 2019. https://rosap.ntl.bts.gov/view/dot/42551.
---------------------------------------------------------------------------

    The vehicle is installed on the chassis dynamometer and is placed 
into driving mode. The vehicle is driven on the dynamometer using the 
vehicle manufacturer-recommended appropriate drive profile for 
discharge and charge of the REESS that would raise the temperature of 
the REESS (with cooling system disabled or reduced function) above its 
safe operating temperature within one hour. If the vehicle manufacturer 
does not supply an appropriate drive profile, NHTSA will drive the 
vehicle over back-to-back aggressive acceleration (near 100% pedal 
application) and decelerations (near or above regenerative braking 
limits) such as the one shown in Figure 3 below, where the vehicle is 
accelerated to 80 mph and then decelerated to 15 mph within 40 seconds.

[[Page 26718]]

[GRAPHIC] [TIFF OMITTED] TP15AP24.046

Figure 3--Drive Profile on Dynamometer To Quickly Raise the Temperature 
of the REESS. (For Illustration Purposes Only)

    Vehicle battery designs and controls mitigate overheating of the 
REESS in different ways: (1) Terminate discharge/charge operations when 
the REESS temperature reaches its operating bounds; (2) Derate (reduce 
acceleration/speed of the vehicle) to prevent the REESS reaching its 
maximum operating temperature; (3) REESS cell chemistries are stable at 
higher REESS temperature. In order to accommodate different approaches 
to address hazards associated with overheating of REESS, GTR No. 20 
provides three different options for terminating the discharge/charge 
cycles:
    (a) the vehicle terminates the charge-discharge cycle,
    (b) the REESS temperature gradient is less than or equal to 4 
[deg]C for a two-hour period, or
    (c) 3 hours have elapsed from the time of starting the discharge-
charge cycles on the chassis dynamometer.
    In accordance with GTR No. 20, the agency proposes to use the same 
three options listed above to terminate the discharge/charge cycle.
    At the conclusion of the over-temperature evaluation, a standard 
cycle is performed if possible. The test concludes with a 1-hour 
observation period in which the vehicle is observed for electrolyte 
leakage, rupture, venting, fire, or explosion. At the conclusion of the 
observation period, the electrical isolation is determined in a similar 
manner as that in FMVSS No. 305 S7.6, using a voltmeter to measure 
voltages.
v. External Short-Circuit Protection
    The purpose of the external short-circuit protection test is to 
verify the performance of the vehicle controls (protection measure) 
against a short-circuit occurring externally to the REESS. During an 
external short-circuit event, large amounts of instantaneous current 
can be readily drawn generating copious amounts of heat. Associated 
safety risks include over-heating, gas venting, or arcing that can 
occur under fault conditions which can potentially lead to fire or 
explosion.
    Vehicle controls or the BMS typically protect the REESS from an 
external short-circuit. GTR No. 20 includes a test to evaluate the 
performance of vehicle controls to protect the REESS from an external 
hard short-circuit (shorting resistance less than 5 milliohms). NHTSA 
tentatively concludes that GTR No. 20's external short-circuit test is 
practical and feasible based on the agency's own testing.\74\ NHTSA 
proposes to include the GTR No. 20 external short-circuit protection 
requirement and test procedure in FMVSS No. 305a.
---------------------------------------------------------------------------

    \74\ See Test reports in Docket No. NHTSA-2021-0029, available 
at www.regulations.gov. Detailed test procedures are provided in the 
test reports of the 2021 Chevrolet Bolt (NHTSA-2021-0029-0001), 2020 
Nissan Leaf (NHTSA-2021-0029-0002), and the 2020 Tesla Model 3 
(NHTSA-2021-0029-0003).
---------------------------------------------------------------------------

    The external short-circuit test is performed on a complete vehicle. 
The SOC of the REESS at the beginning of the test is set at 90 to 95 
percent SOC. The test is conducted at ambient temperatures between 10 
[deg]C and 30 [deg]C. The breakout harness is installed on the vehicle 
at the manufacturer specified location(s).\75\ Temperature probes are 
connected to the REESS case to monitor changes in the REESS 
temperature. Temperature measurements may also be obtained through 
communication with the REESS control module. The short circuit 
contactor (with the contactors in open position) is connected to the 
breakout harnesses. The total resistance of the equipment to create the 
external short circuit (short circuit contactor and breakout harnesses) 
is verified to be between 2 to 5 milliohms.\76\ To begin the short-
circuit evaluation, the short-circuit contactors are closed. The short-
circuit condition is continued until (1) current is no longer present 
or (2) one hour after the temperature probe on the REESS has stabilized 
with a temperature change of less than 4 [deg]C for a two-hour period.
---------------------------------------------------------------------------

    \75\ If the manufacturer does not provide information on the 
location to connect the breakout harness for the external short 
circuit test, the breakout harnesses may be connected on either side 
of the positive and negative terminals of the pack.
    \76\ GTR No. 20 specifies the external short circuit resistance 
not exceeding 5 milliohms. The agency is specifying a range from 2 
to 5 milliohms for ease of conducting the tests and to ensure 
objectivity of the test.
---------------------------------------------------------------------------

    If possible, a standard cycle is performed after termination of the 
short-circuit. Fuses that opened during the short-circuit are not 
replaced, and the standard cycle procedure is not performed if it is 
not possible to charge and discharge the vehicle.
    The vehicle is observed for one hour for electrolyte leakage, 
rupture, venting, fire, or explosion. The external short-circuit test 
concludes with an electrical isolation determination in a similar 
manner as that in current FMVSS No. 305a S7.6 using a voltmeter to 
measure voltages.
vi. Low-Temperature Protection
    Uncontrolled repeated operation at low temperatures, especially 
charging

[[Page 26719]]

for lithium-ion battery chemistries, may result in lithium plating or 
cell damage that could eventually lead to reduced performance or 
degraded life during subsequent operation. While single time operation 
of REESS in very cold temperatures would not lead to a severe event, 
some REESS designs use special chemical reactions which can damage the 
REESS if it is charged at high rates in very cold temperatures. A 
subsequent high rate of charging of such a damaged REESS may lead to 
fire or explosion. Therefore, the rate of charging may need to be 
terminated or limited in very cold temperatures.
    Currently, no practical test procedure is available to evaluate the 
performance of vehicle controls in low temperature conditions because 
the effects of repeated charging at very low temperatures occur over a 
very long period of time. Therefore, GTR No. 20 requires manufacturers 
to provide documentation that includes a system diagram, a written 
explanation on the lower boundary temperature for safe REESS operation, 
the method of detecting REESS temperature, and the action taken when 
the REESS temperature is at or below the lower boundary for safe REESS 
operation.
    NHTSA proposes to include documentation requirements based on GTR 
No. 20 into FMVSS No. 305a. NHTSA proposes that the manufacturer 
provide documentation, upon NHTSA's request, to demonstrate how the 
vehicle monitors and appropriately controls REESS operations at low 
temperatures at or below the lower temperature boundary for safe REESS 
operation. The proposed requirements would indicate how manufacturers 
identify, verify, and ensure vehicles have low-temperature protections 
in place. Specifically, the proposal requires the manufacturer-supplied 
documentation for a specific vehicle make, model, and model year would 
include the following:
    (1) A description of the lower temperature boundary for safe REESS 
operation in all vehicle operating modes.
    (2) A description and explanation of C-rates at the lower 
temperature boundary for safe REESS operation.
    (3) A description of the method used to detect REESS temperature.
    (4) A system diagram with key components and subsystems involved in 
maintaining safe REESS charging and discharging operation for 
temperatures at or below the lower temperature boundary for safe REESS 
operation.
    (5) A description of how the vehicle controls, ancillary equipment, 
and design features were validated and verified for maintaining safe 
REESS operations at or below the lower temperature boundary for safe 
REESS operation.
    (6) A description of the final review/audit process of the 
manufacturer, and the accompanying results of the manufacturer's final 
assessment of risk management, and risk mitigation strategies.
    NHTSA intends these documentation measures to demonstrate that the 
manufacturer has considered, assessed, and mitigated identified risks 
for safe operation of the vehicle. NHTSA tentatively agrees with GTR 
No. 20 that there is a safety need for low temperature protections for 
the REESS. Without protections, uncontrolled repeated operation at low 
temperatures poses an unreasonable risk of fire or explosion. In the 
absence of information enabling NHTSA to propose a practical test 
procedure to evaluate the performance of vehicle controls in low 
temperature conditions, the agency is proposing to require 
manufacturers to submit documentation to NHTSA about pertinent low 
temperature safety hazards, describe their risk mitigation strategies 
for the safety hazards, and how they assessed the effectiveness of 
their mitigation strategies.
    NHTSA would review the documentation to understand the safety 
hazards associated with the particular REESS in the vehicle, see 
whether the manufacturer conducted an assessment of the risks, and 
understand the measures the manufacturer undertook to mitigate those 
known risks. This approach is intended to evolve over time as battery 
technologies continue to rapidly evolve. It is an interim measure 
intended to assure that manufacturers will identify and address the low 
temperature safety risks of the REESS. In section VI., NHTSA requests 
comments on whether the proposed document requirement would be better 
placed in a general agency regulation than in proposed FMVSS No. 305a.
2. Mitigating Risk of Thermal Propagation Due to Internal Short Within 
a Single Cell in the REESS
i. Safety Need
    The potential for thermal runaway is a characteristic of the 
lithium-ion cells currently used in REESSs for electric vehicle 
propulsion. Thermal runaway of a lithium-ion cell in a REESS occurs 
when the thermal stability limit of the cell chemistry is exceeded, and 
the cell releases its energy via an exothermic reaction at an 
uncontrolled rate such that heat is generated faster than it is 
dissipated. The thermal runaway in a single cell may propagate to the 
surrounding cells through conductive, convective, and radiative heat 
transfer modes, causing reactions which create smoke, fire or, in very 
rare circumstances, explosion. Lithium-ion cells have flammable 
electrolyte that upon decomposition provides oxygen to the fire caused 
by the thermal runaway, which increases the likelihood of its 
propagation to other cells and even outside the REESS. The self-
oxygenating fires involving the cells in a REESS are therefore 
difficult to extinguish. The smoke, fire, toxic gas emissions, and 
explosion resulting from the thermal runaway can cause hazardous 
conditions for vehicle occupants and those near the vehicle.
    One root-cause of single-cell thermal runaway (SCTR) and 
propagation due to an internal short-circuit relates to problems within 
the cells. While this NPRM contains many performance tests for the safe 
operation of the REESS, none of these tests would mitigate or prevent 
thermal runaway due to an internal short-circuit within a cell of the 
REESS and subsequent fire propagation. The mechanism of an internal 
short circuit in a cell is complex and requires further study. 
Currently, the risk of a spontaneous internal short circuit is heavily 
dependent on battery design, such as use of non-flammable electrolytes, 
ionic liquids, heat resistant and puncture-proof separators, and anode 
and cathode materials. However, as discussed below, a performance test 
that would establish a minimum standard of performance for the 
materials is not available now.
    GTR No. 20 addresses the hazards associated with SCTR due to an 
internal short circuit through a documentation approach that requires 
manufacturers to provide (to the testing authority) information on risk 
mitigation strategies used in vehicle design to counteract the safety 
risk. GTR No. 20 also requires a warning system to allow vehicle 
occupants sufficient time to egress the vehicle before hazardous 
conditions are present in the passenger compartment due to SCTR within 
the REESS. GTR No. 20 requires documentation of the warning system, and 
requires operation of the warning system only when the vehicle 
propulsion system is turned on.
    NHTSA tentatively generally agrees that a documentation approach on 
risk mitigation strategies currently has merit, given there is no 
suitable performance test to validate mitigation or prevention of SCTR 
within a REESS. NHTSA is proposing a documentation approach based on 
GTR No. 20 but has focused the GTR's requirements to better address 
this safety need pending development of an objective performance test 
that can

[[Page 26720]]

be applied to all REESSs in vehicles. In section VI., NHTSA requests 
comments on whether the proposed document requirement would be better 
placed in a general agency regulation than in proposed FMVSS No. 305a.
    NHTSA is not proposing to require a warning system, or 
documentation of the warning system, as specified in GTR No. 20. As 
explained fully later in this section, NHTSA believes such a 
requirement would not mitigate the safety hazards observed in the 
field.
ii. GTR No. 20 Phase 1 Requirements
    GTR No. 20 recognizes that, in general, REESS cells are 
manufactured with manufacturing controls to mitigate safety problems. 
Based on current manufacturing control processes, the probability of 
manufacturing problems within a cell is generally considered to be less 
than one in a million.\77\ Since the likelihood of two cells in a REESS 
going into spontaneous single-cell thermal runaway (SCTR) 
simultaneously is significantly lower,\78\ the focus of GTR No. 20 is 
to mitigate the hazards associated with SCTR due to an internal short-
circuit within a single cell.
---------------------------------------------------------------------------

    \77\ A REESS consists of a number of cells (n) in the range of 
100 to 500. Therefore, the probability of a single-cell thermal 
runaway and propagation event due to an internal short-circuit is 
estimated to be the product of the number of cells times one in a 
million (n x 10-6). https://batteryuniversity.com/
article/bu-304a-safety-concerns-with-li-
ion#:~:text=Lithium%2Dion%20batteries%20have%20a,than%20those%20in%20
consumer%20products.
    \78\ The probability of two cells simultaneously undergoing 
single-cell thermal runaway and propagation due to an internal 
short-circuit is equal to the product of the probability of a 
single-cell thermal runaway (n\2\ x 10-12).
---------------------------------------------------------------------------

    GTR No. 20 addresses the SCTR safety hazard through a documentation 
approach that requires manufacturers to provide (to the testing 
authority on request) information on risk mitigation strategies used in 
vehicle design to counteract the safety risk, and documentation on a 
warning system that warns occupants to egress the vehicle. The 
documentation requirements for risk mitigation strategies are only 
generally described, however. This is because during the development of 
GTR No. 20, there was no significant evidence of electric vehicle fires 
due to SCTR and propagation due to an internal short-circuit. At that 
time, the thought was that vehicle occupants would be exposed to 
hazardous conditions if the SCTR propagates outside of the REESS to 
other parts of the vehicle. Therefore, GTR No. 20 focuses primarily on 
the warning and less on mitigating the risk of the SCTR within the 
cell. The GTR requires that a warning be provided to the driver 5 
minutes before hazardous conditions are present in the passenger 
compartment due to SCTR and subsequent fire propagation. Five minutes 
was considered sufficient time for vehicle occupants to egress the 
vehicle before exposure to hazardous conditions. Under the GTR, 
manufacturers would satisfy the requirement for a warning by providing 
documentation that the vehicle provides the required warning.
    GTR No. 20 uses a documentation approach for both the risk 
mitigation strategies and the warning because an objective test 
procedure is not available. Existing methods of initiating thermal 
runaway simulating an internal short-circuit within a single cell in a 
REESS are intrusive and dependent on the type of cell chemistry and 
cell type.\79\ Additionally, different methods of initiation could 
result in different results.\80\ NHTSA funded research to evaluate 
different thermal runaway propagation test methods by examining various 
existing methods of initiating thermal runaway, including heating 
element method, rapid heater method, nail penetration, and laser 
method, on batteries with a variety of chemistries, formats, and 
configurations.\81\ The research indicated that the thermal runaway 
initiation methods may influence the test results and the most 
appropriate initiation method for a battery may depend on battery 
chemistries, formats, and configurations.
---------------------------------------------------------------------------

    \79\ One common method of initiating a thermal runaway is to 
heat a cell externally using a heating element. This would require 
disassembly of the casing of the REESS, adhering a heating element 
to the surface of a cell, and adding thermocouples to verify the 
heating element only provides heat to a single cell and not to 
adjacent cells. The amount of heat applied to initiate a thermal 
runaway depends on the cell chemistry (more volatile chemistries 
requiring less heat input), and the cell design/type (thick wall 
cells needing more heat input). The disassembly of the REESS, the 
addition of a heating element, and the heat input is intrusive to 
the REESS.
    \80\ Another method of initiating a thermal runaway in a cell is 
to penetrate a nail into a cell in the REESS. The orientation of the 
nail penetration depends on the cell design and in some instances, 
nail penetration may not cause a thermal runaway. While this method 
may not require the REESS casing to be opened, the penetrating nail 
compromises the casing and the cell structure. Additionally, the 
depth of nail penetration may result in differences in heat release 
that may not be similar in repeat tests and in tests using a heating 
element.
    \81\ Lamb, J., Torres-Castro, L., Stanley J., Grosso, C, Gray, 
L., ``Evaluation of Multi-Cell Failure Propagation,'' Sandia Report 
SAND2020-2802, March 2020. https://www.osti.gov/servlets/purl/1605985.
---------------------------------------------------------------------------

    The repeatability and reproducibility of a potential performance 
test using existing methods of thermal runaway initiation, and whether 
such a test could be conducted on all applicable vehicles, are unknown. 
Due to the rapid development of electric vehicle propulsion technology, 
it was unclear during development of the GTR if any existing 
performance test could apply to future vehicle designs without 
restricting further enhancement of electric vehicle propulsion systems. 
Therefore, instead of specifying a performance test for thermal runaway 
and propagation due to an internal short-circuit in a single cell of a 
REESS, GTR No. 20 requires manufacturers to submit documentation. Such 
documentation must show risk mitigation strategies in their vehicle 
designs for reducing hazards to vehicle occupants associated with 
thermal runaway due to an internal short-circuit in a single cell in 
the REESS. The documentation must also detail how the vehicle's warning 
system activates a warning at least 5 minutes before hazardous 
conditions arise in the passenger compartment.
    Specifically, GTR No. 20 specifies the following documentation 
requirements:
     A description of the warning system.
     Parameters (such as voltage, temperature, or current) that 
trigger the warning indicator (telltale).
     A risk reduction analysis using appropriate industry 
standard methodology (for example, IEC 61508,\82\ MIL-STD 882E,\83\ 
ISO-26262,\84\ fault analysis as in SAE J2929,\85\ or similar), which 
documents the risk to vehicle occupants caused by a single-cell thermal 
runaway triggered by an internal short-circuit leading to thermal 
propagation and the expected risk reduction resulting from 
implementation of the identified risk mitigation functions or 
characteristics.
---------------------------------------------------------------------------

    \82\ IEC-61508:2010, ``Functional Safety of Electrical/
Electronic/Programmable Electronic Safety-related Systems''. https://webstore.iec.ch/searchform&q=IEC%2061508.
    \83\ MIL-STD-882E:2012, ``System Safety''. https://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=36027.
    \84\ ISO-26262 series:2018, ``Road vehicles--Functional 
Safety''. https://www.iso.org/search.html?q=ISO-26262&hPP=10&idx=all_en&p=0&hFR%5Bcategory%5D%5B0%5D=standard.
    \85\ SAE J2929:2013, ``Safety Standard for Electric and Hybrid 
Vehicle Propulsion Battery Systems Utilizing Lithium-based 
Rechargeable Cells''. https://www.sae.org/standards/content/j2929_201302/.
---------------------------------------------------------------------------

     A system diagram of all relevant physical systems and 
components which contribute to the protection of vehicle occupants from 
hazardous effects caused by thermal propagation triggered by a single-
cell thermal runaway event due to an internal short-circuit.

[[Page 26721]]

     A diagram showing the functional operation of the relevant 
systems and components and identifying all relevant risk mitigation 
functions or characteristics.
     For each identified risk mitigation function or 
characteristic:
    [cir] A description of its operation strategy,
    [cir] Identification of the physical system(s) or component(s) 
which implements the function,
    [cir] One or more of the following engineering documents relevant 
to the manufacturers design which demonstrates the effectiveness of the 
risk mitigation function:
    [ssquf] Tests performed including procedure used and conditions and 
resulting data,
    [ssquf] Analysis or validated simulation methodology and resulting 
data.
iii. NHTSA Proposal
    NHTSA tentatively agrees with GTR No. 20's rationale for the 
documentation requirements for risk mitigation of thermal propagation 
events resulting from SCTR due to an internal short-circuit within a 
cell in the REESS. NHTSA tentatively concludes that due to the rapidly 
evolving REESS technology and control systems to manage the performance 
condition and safety of the REESS, a performance test to validate 
mitigation of thermal propagation resulting from SCTR within the REESS 
is not currently feasible. A performance test for a warning, when the 
vehicle propulsion system is turned on, that provides sufficient time 
for vehicle occupants to egress the vehicle before hazardous conditions 
arise in the passenger compartment after a thermal runaway is initiated 
in a cell of the REESS would be unduly design restrictive, not 
applicable to all vehicle/REESS types, and not relevant to real world 
incidents.\86\
---------------------------------------------------------------------------

    \86\ In most real-world incidents resulting in fire due to 
thermal runaway of a single cell in the REESS, the vehicle was 
parked, with propulsion system turned off, and with no occupants in 
the vehicle. In some cases, the vehicles were parked in garages of 
homes. Therefore, a requirement for a warning to vehicle occupants 
in the vehicle with propulsion system turned on would not have 
helped prevent the fire or mitigated hazards to people in homes or 
in the vicinity of the burning parked vehicle.
---------------------------------------------------------------------------

    This NPRM proposes a documentation requirement for FMVSS No. 305a 
to require manufacturers to provide to NHTSA, upon NHTSA's request, 
information about their efforts to identify and address potential 
safety problems with SCTR and propagation due to an internal short-
circuit. The information would be provided by a manufacturer in 
accordance with NHTSA's specified structure in four parts. NHTSA's 
proposed documentation component structure is based on elements from 
the GTR No. 20, ISO-6469-1: Amendment 1 2022-11,\87\ and ISO-26262.\88\ 
The documentation submitted by the manufacturer is required to include 
all known risks to vehicle occupants and bystanders, risk assessment, 
risk management, and risk mitigation strategies in three vehicle 
operational modes (i.e., external charging mode,\89\ active driving 
possible mode,\90\ and parking mode \91\). NHTSA's proposal goes beyond 
GTR No. 20's active driving possible mode to ensure manufacturers 
consider all risks known to it in three vehicle operational modes. The 
assessment and validation of these strategies may involve a combination 
of physical testing and simulations at the component level and/or full 
vehicle level. The reporting requirements would apply to REESSs of all 
types (including REESS with non-flammable electrolyte).
---------------------------------------------------------------------------

    \87\ ISO 6469-1:Third Edition 2019-04 Amendment 1 2022-11, 
``Electrically propelled road vehicles--Safety specifications--Part 
1: Rechargeable energy storage system (RESS),'' specifies safety 
requirements for REESS, including test methodology for initiating 
thermal runaway in a cell for the purpose of conducting a thermal 
runaway propagation test and a format for reporting on risk 
mitigation strategies of thermal propagation resulting from a 
thermal runaway in a single cell of an REESS due to an internal 
short within the cell.
    \88\ ISO 26262: 2018, ``Road vehicles--Functional safety,'' 
provides a comprehensive collection of standards to manage and 
implement road vehicle functional safety from concept phase to 
production and operation. The standard provides guidelines for 
overall risk management, individual component development, 
production, operation, and service.
    \89\ External charging mode is the vehicle operational mode in 
which the charge connector is connected to the vehicle charge inlet 
for the purpose of charging the REESS.
    \90\ Active driving possible mode is the vehicle mode when 
application of pressure to the accelerator pedal (or activation of 
an equivalent control) or release of the brake system causes the 
electric powertrain to move the vehicle.
    \91\ Parking mode is the vehicle mode in which the vehicle power 
is turned off, the vehicle propulsion system and ancillary equipment 
such as the radio are not operational, and the vehicle is 
stationary.
---------------------------------------------------------------------------

    The objective of the documentation is for vehicle manufacturers to 
identify the risks of single-cell thermal runaway and propagation for 
their REESS type, identify strategies to mitigate those risks, and 
demonstrate how those strategies work. The documentation would 
accomplish the following goals:
     It would identify all risks known to the manufacturer 
related to single-cell thermal runaway and propagation due to an 
internal short-circuit;
     It would discuss whether and how each identified risk is 
managed and/or mitigated by at least one risk mitigation strategy;
     It would explain the reasons the manufacturer believes 
each risk mitigation strategy is effective (measures taken to verify 
and/or validate them, including any final review/audit results); and,
     It would identify, describe, and provide any review/audit 
process and results that accompany the final assessment of risk 
management and risk mitigation strategies.
    Proposed provisions to achieve the above goals are discussed in 
detail below.
    The documentation requirement proposed by NHTSA is divided into 
four sections with more detailed requirements than GTR No. 20. Under 
the agency's requirements, in Part I, System Analysis, the vehicle 
manufacturer would provide information describing which conditions 
specific to the vehicle could lead to a SCTR event caused by an 
internal short-circuit. The conditions identified serve as the inputs 
to identify the functions and failure modes for the risk identification 
in Part II.
    Part I would require the following documentation:
     A system diagram and a description of all relevant 
physical systems and components of the REESS, including information 
about the cell type and electrical configuration, cell chemistry, 
electrical capacity, voltage, current limits during charging and 
discharging, thermal limits of the components that are critical for 
thermal propagation safety;
     A system diagram, operational description of sensors, 
components, functional units relevant to single-cell thermal runaway 
due to internal short-circuit and thermal propagation, and the 
interrelationship between the identified sensors, components, and 
functional units;
     A description of conditions under which a single-cell 
thermal runaway and propagation event due to an internal short-circuit 
could occur;
     A description of how the identified conditions are 
allocated to each identified component, functional unit, and subsystem;
     A description of the process used to review the identified 
conditions and their allocation to the identified sensors, components, 
and functional units, for completeness and validity; and
     A description of any system for warning or notification 
prior to the occurrence of thermal runaway in a cell, including a 
description of the detection technology and mitigation strategies, if 
any.
    Part II, Safety Risk Assessment and Mitigation Process, provides a 
description of all identified safety risks and strategies to mitigate 
and manage

[[Page 26722]]

these risks. Part II distinguishes between primary and secondary risk 
mitigation strategies. Primary risk mitigation strategies mitigate the 
risk of SCTR due to an internal short-circuit and the occurrence of 
thermal propagation that may result from SCTR. Primary risk mitigation 
strategies include manufacturing quality control to mitigate defects in 
cells of REESS, REESS design features such as heat sinks, cell spacing, 
coolant, advanced battery management system with prognostics and 
diagnostics systems \92\ to manage the health of the cells of an REESS 
and detect a possible thermal runaway condition before it occurs. In 
contrast, secondary risk mitigation strategies may not reduce the risk 
of thermal runaway or thermal propagation but reduce the hazards 
associated with thermal propagation. Secondary risk mitigation 
strategies include warning systems to vehicle occupants/bystanders and/
or notification to emergency personnel in the event of thermal 
propagation (e.g., automatic notification to 911 operators). NHTSA 
anticipates that secondary risk mitigation strategies would be employed 
as an addition to primary risk mitigation strategies in the overall 
safety strategy.
---------------------------------------------------------------------------

    \92\ Prognostic technologies predict the health of a system or a 
component of a system in the future and diagnostic technologies 
determine a specific problem with a system or component of a system.
---------------------------------------------------------------------------

    Part II would require the following documentation:
     A description of safety risks and safety risk mitigation 
strategies, and how these were identified (e.g., Failure Mode and 
Effects Analysis (FMEA), or Failure Modes, Effects, and Criticality 
Analysis (FMECA)); \93\
---------------------------------------------------------------------------

    \93\ FMEA and FMECA are established methodologies to identify 
failure modes and postulate the effects of those failures on the 
system. Refer to https://www.dau.edu/acquipedia-article/failure-modes-effects-analysis-fmea-and-failure-modes-effects-criticality.
---------------------------------------------------------------------------

     A description of how each risk mitigation manages/
mitigates the identified safety risks.
    In Part III, Verification and Validation of Effective Risk 
Mitigation Strategies, the manufacturer provides information showing 
how they verify the effectiveness of the identified mitigation 
strategies in Part II to mitigate the identified safety risks. The 
vehicle level assessment examines how the entire vehicle monitors and 
mitigates safety risks. The vehicle level assessment is the culmination 
of the verification/validation results of each individual risk 
mitigation strategy.
    Part III would require the following documentation:
     A summary of the process used to verify each identified 
risk is addressed by at least one risk mitigation strategy;
     A description of how each risk mitigation strategy was 
verified and validated for effectiveness; \94\
---------------------------------------------------------------------------

    \94\ Possible verification/validation methods for Part III 
include (but are not limited to) fault injection tests, software, 
and hardware performance tests at component and/or system level, and 
system level performance evaluation using validated mathematical 
models.
---------------------------------------------------------------------------

     A description of the verification and validation results 
for each risk mitigation strategy; and
     A vehicle level assessment evaluating the system response 
to safety risks associated with the REESS. Vehicle level assessment and 
validation could be the use of physical tests and/or validated models/
simulations at a component level scaled up to evaluate the system 
response.
    Part IV, Overall Evaluation of Risk Mitigation, shall address:
     Results of any final review/audit responsible for 
reviewing the technical content, completeness, and verity of the 
documentation submitted by the manufacturer.
    The risk-based methodology outlined above is intended to mitigate 
the safety hazards associated with SCTR and propagation from an 
internal short-circuit. The requirement is intended to ensure that 
manufacturers are aware of the safety risks at issue and have 
considered safety risk mitigation strategies. The documentation 
submitted by the manufacturer will inform NHTSA of the safety risk 
mitigation strategies manufacturers have utilized for the identified 
safety hazards, enable NHTSA to oversee those safety hazards, and 
inform future regulatory measures.. This approach is battery technology 
neutral, not design restricted, and is intended to adapt over time as 
battery technologies continue to rapidly evolve. NHTSA seeks comment on 
the documentation requirements described above. In section VI., NHTSA 
requests comments on whether the proposed document requirement would be 
better placed in a general agency regulation than in proposed FMVSS No. 
305a.
NHTSA's Decision Not To Propose a Warning Requirement
    GTR No.20's warning requirement rationale is that the warning would 
allow vehicle occupants sufficient time to egress the vehicle before 
hazardous conditions are present in the occupant compartment. NHTSA 
does not agree with GTR No.20's rationale for a warning requirement 
related to SCTR due to an internal short-circuit within the cell. NHTSA 
is not proposing to require such a warning system, or documentation of 
the warning system, as specified in GTR No. 20 because such a 
requirement would not mitigate the safety hazards observed in the 
field, as described in detail below.
    Field data and incidents related to SCTR and propagation due to an 
internal short-circuit in lithium-ion REESSs are sparse and anecdotal. 
However, when reviewing the limited number of non-crash and non-abuse 
related electric vehicle fire incidents in the United States,\95\ the 
following trends emerge:
---------------------------------------------------------------------------

    \95\ E.g., Bolt EV Recall Information https://experience.gm.com/recalls/bolt-ev.
---------------------------------------------------------------------------

     The vehicle operation mode is in the usual parking 
mode.\96\
---------------------------------------------------------------------------

    \96\ Usual parking mode is the vehicle operational mode in which 
the main software is ``Off'', the gear selector is in ``P'' (park), 
the energy supply is disconnected, the REESS power line is 
disconnected, the cooling system is not operational, the vehicle 
controls that manage safe operation of the REESS (e.g., Battery 
Manage System) are not energized, and the vehicle occupants are 
typically not present.
---------------------------------------------------------------------------

     The vehicle is parked in a garage attached to a house, a 
parking garage, or on the street.
     The state of charge (SOC) of the REESS was generally in 
the upper range.
    Fire statistics reports by South Korea identified 35 electric 
vehicle fires since 2018, among which 20 electric vehicle fires 
originated in the REESS of the vehicles when the vehicle was parked and 
the SOC was greater than 90 percent.\97\ In the electric vehicle fire 
incidents in the United States and South Korea, the vehicle fire 
propagated to adjacent vehicles and structures with release of copious 
amounts of smoke, resulting in significant property damage. The GTR No. 
20 requirement for a warning to the driver would not have helped 
mitigate the electric vehicle fires and would not have mitigated 
property damage.
---------------------------------------------------------------------------

    \97\ EVS23-E1TP-0200 [KR] EV Fire Records of Korea.pptx. https://wiki.unece.org/display/trans/EVS+23rd+session.
---------------------------------------------------------------------------

    Accordingly, this NPRM does not propose to require a warning to 
occupants or documentation pertaining to a warning, as such 
requirements would not sufficiently address a safety need. NHTSA 
believes the documentation requirements in GTR No. 20 for a warning to 
the driver are not relevant to the field-observed electric vehicle 
fires likely resulting from SCTR. NHTSA believes that vehicle designs 
using a risk mitigation strategy to mitigate or prevent the occurrence 
of SCTR incidents would better address the risks and hazards associated 
with spontaneous electric

[[Page 26723]]

vehicle fires that originate within the REESS than a warning to egress 
the vehicle. This NPRM proceeds with NHTSA's preferred approach which 
would require documentation demonstrating that the manufacturer has 
considered and developed risk mitigation strategies to address SCTR in 
developing their electric vehicles.
GTR No. 20 Phase 2 Test Procedure Currently Under Consideration
    The IWG is continuing work on developing a test-based approach for 
SCTR due to an internal short-circuit in a single cell within the 
REESS. The plan is for a future regulation to require that the thermal 
propagation test procedure fulfill the following conditions:
    1. Triggering of thermal runaway at a single-cell level must be 
repeatable, reproducible, and practicable,
    2. Judgment of thermal runaway through common sensors, e.g., 
voltage and temperature, needs to be practical, repeatable, and 
reproducible, and
    3. Judgment of whether consequent thermal events involve severe 
thermal propagation hazards, needs to be unequivocal and evidence 
based.
    NHTSA discusses this work in the Appendix B to this preamble. 
Comments are requested that could assist the agency in future decisions 
on this matter.
3. Warning Requirements for REESS Operations
    As part of a risk-mitigation approach addressing multiple aspects 
of electrical system safety, NHTSA proposes requiring: (a) a thermal 
event warning; and (b) a vehicle control malfunction warning for 
drivers. The thermal event warning would be assessed by a performance 
requirement, while the vehicle control malfunction warning would be a 
documentation requirement.
i. Thermal Event Warning
    A ``thermal event'' presents an urgent safety critical situation. 
The term refers to a condition when the temperature within the REESS is 
significantly higher (as defined by the manufacturer) than the maximum 
operating temperature specified by the manufacturer. Thermal events 
within REESS could occur due to moisture and dust accumulation within 
the REESS that cause a short circuit at the connections or electronic 
components within the REESS. A thermal event within a battery pack can 
be a safety critical event, as it can lead to smoke, fire, and/or 
explosion. A warning provided about a thermal event within the REESS 
would reduce the likelihood of occupant exposure to smoke, fire, and/or 
explosion.
    GTR No. 20 requires the vehicle to provide a warning to the driver 
in the case of a ``significant thermal event'' in the REESS (as 
specified by the manufacturer) when the vehicle is in active driving 
possible mode.\98\ The GTR does not contain a performance test for the 
warning but instead requires manufacturers to provide documentation on 
the parameters that trigger the warning and a description of the system 
for triggering the warning. Specifically, the documentation 
requirements include:
---------------------------------------------------------------------------

    \98\ Active driving possible mode means the vehicle mode when 
application of pressure to the accelerator pedal (or activation of 
an equivalent control) or release of the brake system causes the 
electric power train to move the vehicle.
---------------------------------------------------------------------------

    (1) Parameters and associated threshold levels that are used to 
indicate a thermal event (e.g., temperature, temperature rise rate, SOC 
level, voltage drop, electrical current, etc.) to trigger the warning.
    (2) A system diagram and written explanation describing the sensors 
and operation of the vehicle controls which manage the REESS in the 
event of a thermal event.
NHTSA Proposal
    NHTSA proposes to include a requirement for an audio and visual 
warning to the driver if a thermal event occurs in the REESS during the 
active driving possible mode. Instead of a documentation requirement as 
in the current GTR No. 20, NHTSA proposes a performance test to 
evaluate the required warning of a thermal event originating within the 
REESS.
    NHTSA proposes to initiate the thermal event in the REESS by 
inserting a heater within the REESS that achieves a peak temperature of 
600[deg]C within 30 seconds. In the proposed test procedure, the REESS 
is removed from the vehicle, if possible, and the REESS casing is 
opened to attach the heater to a cell or cells in the REESS in a manner 
to put at least one cell in the REESS into thermal runaway. In this 
test, there is no need to restrict heating to a single cell within the 
REESS as the test is verifying activation of a warning when a thermal 
event occurs in the REESS regardless of the cause (e.g., an electric 
short between electronic components in the REESS, thermal runaway of 
multiple cells, etc.). Following installation of the heater in the 
REESS, the REESS casing is closed, the REESS is re-installed in the 
vehicle, and the vehicle propulsion system is turned on. The heater 
within the REESS is then activated. NHTSA proposes that the audio-
visual warning must be activated within three minutes \99\ of 
initiating the heater in the REESS. NHTSA has tentatively decided not 
to specify characteristics of the audio-visual warning to provide 
flexibility in how manufacturers communicate this safety critical 
information to vehicle occupants so they quickly egress the vehicle.
---------------------------------------------------------------------------

    \99\ 3 to 5 minutes is considered to be sufficient time for able 
body individuals to evacuate light and heavy passenger vehicles 
before the occurrence of a hazardous event. https://one.nhtsa.gov/reports/0900006480b01bbc.pdf.
---------------------------------------------------------------------------

    The proposed test is for evaluating appropriate activation of a 
required warning system when there is a thermal event in the REESS that 
could be hazardous to vehicle occupants.\100\ NHTSA tentatively 
concludes that the proposed performance test to evaluate the warning 
system would not be design restrictive and can be conducted on all 
applicable vehicles. Therefore, a performance test is proposed instead 
of adopting the documentation requirement in GTR No. 20. NHTSA seeks 
comment on the merits of the proposed performance test to evaluate the 
thermal event warning system instead of the documentation requirement 
in GTR No. 20. In addition, NHTSA seeks input on the type of heater, 
the heater characteristics (power, peak temperature) and possible 
locations of the heater within the REESS to simulate a thermal event to 
trigger the warning. While this NPRM does not require specific features 
of the audio-visual warning itself, comments are requested on what 
characteristics an effective audio-visual warning should have.
---------------------------------------------------------------------------

    \100\ This is unlike the risk management approach for SCTR where 
the goal is to mitigate hazards of thermal propagation (fire, smoke, 
gas emissions). Because risk management strategies for mitigating 
thermal propagation hazards due to SCTR differ considerably in 
vehicle designs, an objective performance test that can be conducted 
on all applicable vehicles is not available and so a documentation 
requirement is proposed.
---------------------------------------------------------------------------

ii. Warning in the Event of Operational Failure of REESS Vehicle 
Controls
    NHTSA is proposing to require that drivers be warned if there is a 
malfunction of vehicle controls that manage the safe operation of the 
REESS. This NPRM proposes a documentation approach for this type of 
warning, similar to GTR No. 20.
    GTR No. 20 specifies that when the vehicle is in the active driving 
possible mode, the vehicle shall provide a warning telltale to the 
driver in the event of a malfunction of the vehicle controls that 
manage the safe operation of the REESS. GTR No. 20 requires 
manufacturers to provide

[[Page 26724]]

documentation demonstrating that a warning to the driver will be 
provided in the event of malfunction of one or more aspects of vehicle 
controls that manage REESS safe operation. Specifically, vehicle 
manufacturers shall make the following documentation available to the 
testing authority:
    (1) A system diagram that identifies all the vehicle controls that 
manage REESS operation. The diagram must identify what components are 
used to generate a warning telltale indicating malfunction of vehicle 
controls to conduct one or more basic operations.
    (2) A written explanation describing the basic operation of the 
vehicle controls that manage REESS operation. The explanation must 
identify the components of the vehicle control system, provide 
description of their functions and capability to manage the REESS, and 
provide a logic diagram and description of conditions that would lead 
to triggering the warning telltale.
NHTSA Proposal
    Vehicle controls manage several REESS operations, some of which are 
safety critical. There are multiple external fault scenarios \101\ that 
could trigger a vehicle control to take corrective actions to ensure 
safe REESS operations. This NPRM includes performance requirements to 
address these external fault scenarios that assume proper functioning 
of the vehicle controls that manage safe REESS operations. However, if 
the vehicle controls that manage safe REESS operation are not 
functioning properly, the REESS may not be adequately protected from 
fault scenarios, which could lead to REESS degradation and eventually 
result in thermal propagation and other safety hazards. Therefore, it 
is important to notify the driver or front row occupants in the event 
there is malfunction of these vehicle controls that manage safe REESS 
operations.
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    \101\ These fault scenarios include overcharge, over-discharge, 
overcurrent, external short-circuit, and overheating of the REESS.
---------------------------------------------------------------------------

    Due to the complexity and varied designs of vehicle controls that 
manage REESS safe operation, no single test procedure could be 
developed that would fully evaluate whether a warning turns on in the 
event of operational failure of vehicle controls. Therefore, in 
accordance with GTR No. 20, this NPRM proposes to require manufacturers 
to provide a visual warning to the driver (e.g., like a check engine 
light) and documentation demonstrating that the visual warning will be 
provided in the event of operational failure of one or more aspects of 
vehicle controls that manage REESS safe operation.
    NHTSA proposes the GTR No. 20 requirements for a visual warning to 
the driver of any malfunction of the REESS vehicle controls, and 
manufacturer documentation. In addition, NHTSA proposes to include two 
additional requirements that ensure manufacturers have validated 
functionality of the warning system:
    (1) Any validation test results by the vehicle manufacturer to 
confirm a visual warning is displayed in the presence of malfunction of 
the REESS operation vehicle controls.
    (2) A description of the final manufacturer review or audit process 
and results of any final review or audit evaluating the technical 
content and the completeness and verity of the documentation submitted 
by the manufacturer.
    NHTSA tentatively concludes that a documentation approach is 
merited to demonstrate that the manufacturer has considered the 
effectiveness of a visual warning of the malfunction of the REESS 
operational vehicle controls. In the absence of information enabling 
NHTSA to propose a practical test procedure to evaluate the performance 
of a warning, the documentation approach ensures that manufacturers are 
aware of the safety risks at issue and have considered ways to address 
the risks. NHTSA would review the documentation to understand the 
visual warning associated with the particular REESS in the vehicle, see 
whether the manufacturer conducted an assessment of its effectiveness, 
and understand the measures the manufacturer undertook to validate such 
performance.
    This approach is an interim measure intended to assure that 
manufacturers will identify, address, and validate the effectiveness of 
their visual warnings that help manage safe REESS operation. The 
approach is intended to evolve over time as battery technologies and 
NHTSA's information about the REESS safety risk mitigation strategies 
evolve. In section VI., NHTSA requests comments on whether the proposed 
document requirement would be better placed in a general agency 
regulation than in proposed FMVSS No. 305a.
4. Protection Against Water Exposure
    NHTSA proposes to adopt GTR No. 20's physical water test 
requirement, where a vehicle shall maintain electrical isolation 
resistance after the vehicle is exposed to water under normal vehicle 
operation, such as in a car wash or while driving through a pool of 
standing water. However, the agency is not proposing to adopt GTR No. 
20's two other water exposure methods: documentation measures and 
warning requirements.
    Environmental effects such as exposure to water and moisture may 
deteriorate the electrical isolation of high voltage components in the 
powertrain. This may first lead to an electric system degradation and 
eventually lead to an unsafe electrical system for vehicle occupants, 
operators (during charging) or by-standers. Under extreme conditions, 
fire can originate from compromised electrical components due to water 
ingress. GTR No. 20 contains water exposure shock protection 
specifications in which a vehicle shall maintain electrical isolation 
resistance after the vehicle is exposed to water under normal vehicle 
operation, such as during a car wash or driving through a pool of 
standing water.
    NHTSA begins by noting that GTR No. 20 does not have specific 
requirements to address vehicle fires due to vehicle submersion such as 
floods and storm surges, and this NPRM is not covering that area. 
Floods are considered as catastrophic events, and as noted above, one 
of the principles for developing GTR No. 20 was to address unique 
safety risks posed by electric vehicles and their components to ensure 
a safety level equivalent to conventional vehicles with internal 
combustion engine (ICE). NHTSA continues to research the area of REESS 
performance post-submersions. This issue is discussed in more detail 
later in this section.
GTR No. 20 Requirements
    GTR No. 20 contains water exposure shock protection specifications 
in which a vehicle shall maintain electrical isolation resistance after 
the vehicle is exposed to water under normal vehicle operation. GTR No. 
20 specifies three compliance options contracting parties may use in 
their regulations:
     Physical tests--(1) the vehicle is subjected to normal 
washing using a hose nozzle and conditions in accordance with IPX5, 
after which (2) the vehicle is driven in a freshwater wade pool (10 cm 
depth) over a total distance of 500 m at a speed of 20 km/hr for 
approximately 1.5 minutes (min). The electrical isolation of high 
voltage sources in the electric powertrain are verified at the 
conclusion of each test and once again after 24 hours.
     Documentation--The vehicle manufacturers provide 
documentation

[[Page 26725]]

certifying to IPX5 \102\ level waterproofing for protection of high 
voltage components in the vehicle. IPX5 is a waterproof rating that 
ensures protection against water ingress under sustained low pressure 
water jet stream (12.5 liters per minute at a pressure of 30 
kilopascals (4.4 psi) from a distance of 3 meters) from any angle. The 
duration of the jet stream exposure is 1 minute per square meter 
surface area of the high voltage component.
---------------------------------------------------------------------------

    \102\ IEC 60529:1989/AMD2:2013, ``Degrees of protection provided 
by enclosures (IP Code).'' https://webstore.iec.ch/publication/2446.
---------------------------------------------------------------------------

     Warning--The vehicle has an electrical isolation loss 
warning system that warns the driver when electrical isolation falls 
below 100 ohms per volt for DC electrical components or 500 ohms per 
volt for AC electrical components. This option is available for 
individual countries to adopt if they so choose.
i. NHTSA Proposal
    NHTSA tentatively concludes that the GTR No. 20's physical test 
option is a practical and feasible means of evaluating the effects of 
water exposure under normal vehicle operating conditions. It has 
advantages of a performance standard in assessing compliance over a 
documentation approach. Thus, the agency is not proposing the 
compliance option in GTR No. 20 of providing documentation on high 
voltage components meeting IPX5 level of protection.
    Regarding the electrical isolation loss warning system option in 
GTR No. 20, NHTSA believes the warning signals alone are not sufficient 
for addressing loss of electrical isolation concerns. Where objective 
performance criteria are available and are appropriate for all types of 
vehicles to which the standard applies, NHTSA believes objective 
performance criteria should govern when compared to the approach of 
solely using a warning. The existence of the visual warning cannot 
necessarily be considered a safety prevention system, as the root cause 
of the safety hazard remains unaddressed, and the visual warning may be 
ignored by the driver. Although visual warning indicators triggered 
from an isolation monitoring system could help mitigate safety 
concerns, NHTSA believes that this approach is not sufficient to solely 
mitigate a shock or fire hazard caused by the effects of water 
exposure. Thus, the agency does not propose this alternative as a 
compliance option in FMVSS No. 305a.
NHTSA Proposed Vehicle-Level Physical Test Procedures
    The proposed physical test procedure is comprised of two series of 
tests, informally referred to as the ``vehicle washing'' test and the 
``driving through standing water'' test. Electrical isolation is 
determined at the conclusion of each test, and once again after 24 
hours.
A. Vehicle Washing Test
    The washing test exposes the vehicle to a stream of water such as 
when washing a car. The vehicle external surface, including the vehicle 
sides, front, rear, top, and bottom is exposed to the water stream. GTR 
No. 20 excludes the vehicle underbody from exposure to the water 
stream. However, since the vehicle underbody is often exposed to water 
when the vehicle is washed, NHTSA proposes to also expose the vehicle 
underbody to the water stream to make this test more representative of 
vehicle washing. The areas of the vehicle that are exposed to the water 
stream in any possible direction include border lines, i.e., a seal of 
two parts such as flaps, glass seals, outline of opening parts 
(windows, doors, vehicle inlet cover), outline of front grille and 
seals of lamps.
    During the test, the vehicle is sprayed from any practicable 
directions with a stream of freshwater from a standard test nozzle as 
shown in Figure 4 below. The standard nozzle, with an internal diameter 
is 6.3 mm, shall provide a delivery rate of 11.9-13.2 liters/minute (l/
min) with water pressure at the nozzle of 30-35 kilopascals (kPa) or 
0.30-0.35 bar. These standard nozzle specifications are from IEC 60529 
for IPX5 water jet nozzle.
[GRAPHIC] [TIFF OMITTED] TP15AP24.047

Figure 4--Standard Nozzle (IEC 60529) for IPX5 Water Exposure Test

    The vehicle surface is exposed to the water stream from the 
standard nozzle for a duration of 1 minute per square meter or for 3 
minutes, whichever is greater. The distance from the nozzle to the 
tested vehicle is 3 meters, which may be reduced, if necessary, to 
ensure the surface is wet when spraying upwards.
    After the ``vehicle washing'' test and with the vehicle surface 
still wet, electrical isolation is determined for high voltage sources 
in the same manner as that currently in S7.6 of FMVSS No. 305. The high 
voltage sources are required to meet the electrical isolation 
requirements as specified in S5.4.3 of current FMVSS No. 305.
    Comments are requested on the merits of including the test in FMVSS 
No. 305a. NHTSA seeks comment on the representativeness of the washing 
test, including but not limited to the proposed test conditions (e.g., 
30-35

[[Page 26726]]

kPa versus 80-100 kPa water pressure conditions, water salinity levels, 
and water exposure durations, etc.).
B. Driving Through Standing Water Test
    NHTSA proposes that vehicles should also be subjected to GTR No. 
20's ``driving through standing water'' test. The vehicle is driven 
through a pool of standing freshwater,\103\ 10 centimeters (cm) (4 
inches) deep, for a total range of 500 meters (m), at a vehicle speed 
of 20 km/hr.\104\ The pool represents a low-lying portion of a road 
that can get flooded in excessive rain. Meeting the test is a 
reasonable indication that the vehicle has safeguards to ensure 
electrical safety when driven through roads in inclement weather.
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    \103\ Freshwater means water containing less than 1,000 
milligrams per liter of dissolved solids, most often salt.
    \104\ NHTSA tentatively concludes that the 10 cm (approximately 
four-inch) depth is reasonable, as national weather advisories 
(https://www.weather.gov/tsa/hydro_tadd) recommend not driving on 
flooded roads with more than four inches of water. Six inches of 
water on the road could reach the bottom of most passenger cars 
causing loss of control and possible stalling. A foot of water can 
float many vehicles.
---------------------------------------------------------------------------

    If the wade pool used is less than 500 m in length, then the 
vehicle is driven through the wade pool several times. The total time, 
including the periods outside the wade pool, would have to be less than 
5 minutes. GTR No. 20 specifies a maximum test time of 10 minutes, but 
NHTSA believes that 5 minutes is preferable. Traversing 500 m at 20 km/
hr takes 90 seconds. A maximum test duration of 10 minutes would allow 
for an excessive amount of time out of the water and may not be 
equivalent to a continuous 500 m exposure. NHTSA seeks comment on the 
maximum duration of this test. NHTSA also seeks comment on the 
availability and geometric dimensions of different types of wade pools 
(long rectangular, circular) to accomplish this type of test.
    Just after the standing water test is completed and with the 
vehicle still wet, the vehicle would be required to meet the electrical 
isolation requirements now specified in FMVSS No. 305 S5.4.3 when 
tested in the same manner as described in S7.6 of current FMVSS No. 
305. The vehicle is also required to meet the electrical isolation 
requirements that are in S5.4.3 of current FMVSS No. 305, 24 hours 
after the washing test and the standing water test are completed.
    NHTSA seeks comment on the water salinity requirements for the 
physical tests as described above, including tolerances for the test 
parameters listed above.
ii. NHTSA's Consideration of Submersions
    In the U.S., floods resulting from Hurricane Sandy (2012), 
Hurricane Harvey (2017) and Hurricane Ian (2022) have led to electric 
vehicles submerged in flood waters for varying periods of time, with 
varying reports of vehicle fires in the aftermath. In developing this 
NPRM, the agency considered whether it could propose requirements to 
address these types of vehicle submersions and the resulting risk of 
fire. NHTSA analyzed field data from these hurricanes and made the 
following key observations of vehicle fires resulting from the vehicle 
submersions:
    (1) Not all electric vehicles submerged in floods catch on fire. 
The type of water (water salinity), the level of submersion, and 
duration of submersion are likely factors;
    (2) Fire and other hazards are more likely after water exposure 
(days after flood waters recede) rather than during the exposure;
    (3) Fire may not originate in the REESS and may spread to the REESS 
from another vehicle component; and
    (4) While 12V systems may also short circuit and result in vehicle 
fire, fires involving lithium-ion REESS are more difficult to 
extinguish and more hazardous because of the self-oxygenating nature of 
the lithium-ion cells and the energy density of the REESS.
    NHTSA evaluated the regulatory approaches taken by other countries 
to determine if such standards could assist NHTSA in addressing the 
challenges posed by the submersions and fires resulting from Hurricanes 
Sandy, Harvey, and Ian. NHTSA analyzed China and Korea's water exposure 
requirements but determined the focus of those standards do not appear 
to address the safety matter at issue. Key observations and findings 
from the field data in the U.S. and the exploratory investigation into 
the water exposure posed by the hurricanes suggest that the test 
procedure and parameters and the performance requirements in China GB-
38031 \105\ and the Korean Motor Vehicle Safety Standard (KMVSS) \106\ 
may not be representative of field events of vehicle fires resulting 
from Hurricanes Sandy, Harvey, and Ian water exposure. If the standards 
are not representative of the harm NHTSA wishes to address from the 
hurricanes, the concern is the countermeasures to meet the performance 
test requirements of GB-38031 and KMVSS may not be effective at 
mitigating thermal events resulting from the water exposure at 
issue.\107\
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    \105\ GB-38031 water immersion test contains two options. Option 
1 is based on ISO-6469-1:2019 where the REESS is submerged in 1 
meter of seawater (salinity of 3.5 percent) for two hours. The 
performance requirement for this test option is for no fire or 
explosion of the REESS during the submersion. Option 2 is based on 
ISO-20653, and requires IPX7 level waterproofing. In this test 
option, the REESS is completely submerged in regular water for 30 
minutes such that the lower point of the battery is one meter below 
the surface or the highest point is 150 mm below the surface (for 
battery packs with a height greater than 850 mm). The performance 
requirement in this test option is for no water ingress, fire, or 
explosion, and the REESS maintains an electrical isolation of 100 
ohms per volt after submersion. Option 1 of GB-38031 is intended for 
most current REESS (open-type or partially sealed) while Option 2 
would necessitate a fully sealed REESS.
    \106\ KMVSS contains requirements for REESS, including a water 
immersion test that has been implemented in South Korea since 2009. 
In the water immersion test, the REESS is fully submerged in 
seawater (salinity of 3.5 percent) for one hour. The performance 
requirement in this test is for the REESS to not explode or catch on 
fire during the immersion. EVS19-E4WI-0300 [KR] Water Immersion 
Test.pptx. https://wiki.unece.org/display/trans/EVS+19th+session.
    \107\ For instance, NHTSA's understanding is that most of the 
vehicles involved in Hurricane Ian's post-submersion fires had met 
China GB-38031.
---------------------------------------------------------------------------

    Specifically, in both standards, the REESS is submerged in 3.5 
percent salinity water representing seawater for a long period of time 
(two hours for GB-38031 and one hour for KMVSS). NHTSA's exploratory 
investigation of current REESS designs \108\ suggests submersion in 
lower salinity water for a shorter duration may result in higher risk 
of thermal event. Longer immersion times in seawater salinity levels 
allow the batteries to safely discharge under water without adverse 
reactions such as arcing, venting, or underwater fires. Additionally, 
the requirements for no fire and explosion in these two standards are 
evaluated during the REESS immersion and not after the REESS is pulled 
out of the water. Such a requirement is not relevant to the electric 
vehicle fires observed after the flood waters in Hurricane Sandy and 
Hurricane Ian receded.
---------------------------------------------------------------------------

    \108\ Li-Ion Battery Pack Immersion Exploratory Investigation, 
DOT HS 813 136, July 2021. https://rosap.ntl.bts.gov/view/dot/57013.
---------------------------------------------------------------------------

    NHTSA acknowledges that the batteries in conventional vehicles with 
internal combustion engines (ICE) may also catch fire due to 
submersion. However, the post-submersion vehicle fires after Hurricane 
Ian demonstrated that electric vehicle fires are more difficult to put 
out and therefore more hazardous than ICE vehicle fires. NHTSA believes 
that a better understanding of the field incidences of electric vehicle 
fires is needed before a field relevant test and performance 
requirements can be developed that addresses the observed safety risks

[[Page 26727]]

associated with submersion of REESS and high voltage components in 
events such as floods.
    The agency seeks comment on test conditions and test procedures 
that would address observed safety risks associated with submersion of 
REESS and high voltage components.
Going Forward
    Shortly after Hurricane Ian, NHTSA and other DOT agencies 
coordinated with emergency personnel in Florida to collect in-depth 
information on vehicle fire incidences and REESSs involved in the 
flooding.\109\ This activity and others like it provided critical 
information that informed approaches to better protect vehicle owners, 
responders, and other stakeholders in the future.
---------------------------------------------------------------------------

    \109\ NHTSA has purchased ten electric vehicles damaged during 
Hurricane Ian and plans to perform a teardown analysis to understand 
the root cause of the vehicle fires. The teardown analysis will 
inform the next steps to address the safety risks associated with 
vehicle submersions.
---------------------------------------------------------------------------

    In the near term, as discussed in sections below, this NPRM 
proposes to require that electric vehicle manufacturers submit 
standardized emergency response information to a NHTSA central 
depository, to assist first and second responders to respond to 
emergencies as quickly and safely as possible. The agency tentatively 
concludes that such a requirement would be an important and achievable 
near-term measure that NHTSA and the industry can take to mitigate the 
harm from these fires as work continues on vehicle-based mitigation 
methods. As part of NHTSA's activity going forward, NHTSA will document 
EV battery conditions after catastrophic flooding events and will 
commence new research into mitigation methods. The agency will obtain 
data to develop and improve EV tests relevant to salt-water immersion.
5. Miscellaneous GTR No. 20 Provisions Not Proposed
    There are several GTR No. 20 provisions for REESS performance 
during normal vehicle operations that NHTSA has not included in this 
NPRM. These provisions relate to requirements for: vibration, thermal 
shock and cycling, fire resistance, and low state-of-charge (SOC). 
Below is a description of the requirements and explanations of why 
NHTSA is proposing not to include the requirements. NHTSA requests 
comments on these views.
i. REESS Vibration Requirements
    GTR No. 20 contains a vibration requirement and test procedure to 
verify the safety performance of the REESS under a prescribed 
sinusoidal vibration environment that applies a generic vibration 
profile to the tested vehicle. NHTSA believes the vibration profile 
accelerations and frequencies are unique for each vehicle model and so 
applying a generic vibration profile to all vehicle models may not be 
appropriate. Additionally, the vibration environment in the test 
specified in GTR No. 20 is applied only in the vertical direction while 
in real world driving conditions, the REESS is subject to vibration 
along all three orthogonal axes. Therefore, the agency tentatively 
concludes that the vibration test in GTR No. 20 is not representative 
of the actual vibration environment for different vehicle models, or 
representative of real-world conditions that the REESS experiences.
    Furthermore, vibration appears sufficiently addressed through other 
means. The market addresses this matter, as manufacturers routinely 
perform vibration testing to ensure customer satisfaction and 
reliability. Vehicle manufacturers assess the durability of the vehicle 
and its components (not just the REESS) through various road conditions 
with full vehicle simulation, either by driving on a rough road test 
track or simulating the lifetime fatigue on a vibration rig. Further, 
at the component level, electric vehicle batteries are currently 
subject to similar vibration test requirements for transportation under 
the United States Hazardous Materials Regulations (HMR) \110\ but along 
all three orthogonal axes and for frequencies up to 200 Hz.\111\ Thus, 
NHTSA believes that the GTR No. 20 vibration test would not address an 
additional safety need beyond what is already provided by HMR.
---------------------------------------------------------------------------

    \110\ 49 CFR parts 171 to 180, incorporated requirements for 
lithium batteries from UN 38.3 ``Transport of dangerous goods: 
manual tests and criteria.''
    \111\ 49 CFR 173.185 incorporated the vibration test 38.3.4.3 
from the UN's ``Recommendations on the Transport of Dangerous Goods, 
Manual of Tests and Criteria,'' https://digitallibrary.un.org/record/483552?ln=en.
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    For the reasons stated in the paragraph above, NHTSA is not 
proposing the vibration test at a component level or the vehicle 
level.\112\ Currently, during Phase 2 development of GTR No. 20, there 
are discussions for updating the vibration test to include vibration in 
all three orthogonal axes and at higher amplitudes and frequency range. 
In Appendix B of this preamble, the agency seeks public comment on the 
work in Phase 2 on the vibration test.
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    \112\ NHTSA and Transport Canada discussed in detail their 
positions for not including this vibration test during the 
development of GTR No. 20. See https://wiki.unece.org/download/attachments/117508721/EVS21-E3VP-0101%5BOICA_UC_CA%5Dconsideration_of_vibration.pdf?api=v2.
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ii. REESS Thermal Shock and Cycling
    GTR No. 20's thermal shock and cycling requirement and test 
procedure aim to verify that the REESS is robust against thermal 
fatigue and contact degradation caused by temperature changes and 
potential incompatibilities of materials with varying thermal expansion 
characteristics.
    At the component level, REESSs are already subject to thermal 
cycling test requirements for transportation under the HMR. 49 CFR 
173.185 requires lithium-ion cells and batteries to comply with the 
test requirements in UN 38.3, including Test T2: Thermal test, which is 
the basis of the GTR No. 20 thermal shock and cycling test. In the 
UN38.3 Test T2, the REESS would be subject to temperature changes from 
-40 [deg]C to +75 [deg]C. This temperature range is greater than that 
prescribed in GTR No. 20. To avoid redundancy, NHTSA is not proposing 
the thermal shock and cycling test for the REESS. NHTSA tentatively 
concludes that incorporating the GTR No. 20 thermal shock and cycling 
test into FMVSS would not address additional safety needs beyond that 
already provided by HMR and 49 CFR 173.185. The agency seeks public 
comment on the safety need of a REESS thermal shock and cycling 
requirement, and requests commenters provide data to substantiate their 
comments and/or assertions.
iii. REESS Fire Resistance
    This GTR No. 20 requirement is based on UN Regulation No. 34, 
``Uniform provision concerning the approval of vehicles with regard to 
the prevention of fire risks,'' \113\ which contains a fire resistance 
requirement for liquid fueled vehicle with plastic tanks. This test is 
required for REESSs installed in a vehicle at a height lower than 1.5 m 
above the ground and contain flammable electrolyte. During the test, 
the REESS is placed on a grating table positioned above the fire source 
in a pan. The pan filled with fuel is placed under the REESS in such a 
way that the distance between the level of the fuel in the pan and the 
bottom of the REESS corresponds to the design height of the REESS above 
the road surface at the unladed mass. The REESS is exposed directly to 
the flame for 70 seconds. A screen made of refractory material is then 
moved over the pan with the flame,

[[Page 26728]]

such that the REESS is indirectly exposed to the flame for an 
additional 60 seconds. The screen and pan are then moved away from the 
REESS. The REESS is observed until the surface temperature of the REESS 
has decreased to the ambient temperature of the test environment. 
During the test, the REESS shall exhibit no evidence of explosion.
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    \113\ UN Regulation No. 34. https://unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/2013/R034r2e.pdf.
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    NHTSA tentatively concludes that the short duration of the GTR No. 
20 fire resistance test would not address any safety risks associated 
with explosion resulting from external fire to the battery pack. 
Transport Canada conducted full vehicle gasoline pool fire tests of 
electric powered vehicles and similar vehicles with internal combustion 
engines and found that there was no explosion in tests of vehicles with 
REESS and those without. The Transport Canada tests indicated that the 
short duration of the GTR No. 20 external fire test would not result in 
explosion.\114\ During Phase 1 of the GTR No. 20 discussions, the 
United States and Canada noted that including the short duration 
component level test in GTR No. 20 would not address a safety need and 
recommended removing it from GTR No. 20.\115\ For these reasons, NHTSA 
is tentatively not proposing the short duration fire resistance test 
from GTR No. 20. The agency seeks comment on excluding this fire 
resistance requirement from the FMVSS, and requests commenters provide 
data to substantiate their comments and/or assertions.
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    \114\ https://wiki.unece.org/download/attachments/29884786/EVSTF-07-02e.pdf?api=v2.
    \115\ https://wiki.unece.org/download/attachments/29884786/EVSTF-07-02e.pdf?api=v2.
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iv. Low State-of-Charge (SOC) Telltale
    GTR No. 20 requires a telltale to the driver in the event of low 
REESS SOC.\116\ The agency is tentatively not including this telltale 
requirement for electric powered vehicles because there is no 
corresponding low fuel warning requirement for conventional vehicles 
with internal combustion engines. Low-fuel telltales are presently 
provided in all conventional vehicles due to consumer demand. 
Similarly, all electric-powered vehicles already provide low SOC 
telltales due to consumer demand. NHTSA seeks comment on whether this 
GTR No. 20 requirement should be incorporated into proposed FMVSS No. 
305a, and if yes, what the telltale should look like.
---------------------------------------------------------------------------

    \116\ The GTR does not standardize the appearance of the 
telltale.
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IV. Request for Comment on Applying FMVSS No. 305a to Low-Speed 
Vehicles

    Current FMVSS No. 305 applies to electric vehicles whose speed, 
attainable over a distance of 1.6 kilometers (km) (1 mile) on a paved 
level surface, is more than 40 km/h (25 miles per hour (mph)). It does 
not apply to vehicles that travel under 40 km/h (25 mph), such as low-
speed vehicles.\117\
---------------------------------------------------------------------------

    \117\ ``Low-speed vehicle'' is defined in 49 CFR 571.3. See also 
FMVSS No. 500, ``Low speed vehicles,'' 49 CFR 500.
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    There are low-speed vehicles that are also electric-powered 
vehicles. NHTSA requests comments on applying aspects of FMVSS No. 305a 
to low-speed vehicles to ensure a level of protection against shock and 
fire, particularly during normal vehicle operation, and to assure the 
safe operation of the REESS. The agency requests comment on the 
possible applicability of FMVSS No. 305a to low-speed vehicles and its 
relevant safety needs, including any supporting research on low-speed 
vehicles.

V. Emergency Response Information To Assist First and Second Responders

    Fires in electric vehicles are harder to extinguish than fires in 
vehicles with internal combustion engines and can reignite. These risks 
are also dependent on the specific vehicle design. Easy access to 
pertinent vehicle specific and emergency response information is vital 
for first and second responders when encountering electric vehicles. 
Safety is impeded when first and secondary responders are on scene but 
are delayed in their mitigation efforts because information on vehicle-
specific safety mitigation methods are not easily accessible.

a. NTSB Report

    In 2020, NTSB published a safety report following a detailed 
investigation of four electric vehicle fires.\118\ The investigation 
identified safety risks to first and second responders \119\ from 
exposure to high voltage components and from vehicle fire due to 
damaged cells in the REESS that could reignite as a result of stranded 
energy in the REESS.\120\ The NTSB investigation further identified the 
lack of a clear and standardized format in vehicle manufacturers' 
emergency response guides (ERGs) \121\ and inadequacy in the 
information provided in the ERGs for first and second responders to 
minimize safety risks posed by stranded energy in the REESS while 
handling electric vehicles.
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    \118\ Three of the vehicle fires occurred following severe 
crashes that resulted in significant damage to the REESS casing. One 
vehicle fire was caused by internal failure of the REESS during 
normal driving operations. ``Safety risks to emergency responders 
from lithium-ion battery fires in electric vehicles,'' Safety Report 
NTSB/SR-20/01, PB2020-101011, National Transportation Safety Board, 
https://www.ntsb.gov/safety/safety-studies/Documents/SR2001.pdf.
    \119\ The NTSB report states, ``First responders in this context 
refers to firefighters, but emergency medical technicians, 
paramedics, and police officers are also classified as first 
responders. Second responders in this context refers to tow truck 
drivers or tow yard operators, but they can also include those 
responsible for temporary traffic control or other support functions 
at a crash site.''
    \120\ Stranded energy is the energy remaining inside the REESS 
after a crash or other incident. Cells in a compromised REESS could 
undergo thermal runaway at a later time and reignite the vehicle 
fire after firefighters extinguish the initial vehicle fire.
    \121\ Emergency Response Guides (ERGs) contain in-depth vehicle-
specific information related to fire, submersion, leakage of fluids, 
towing, and storage of vehicles. The information is presented in a 
specific format with color-coded sections in a specific order to 
help first and second responders quickly identify pertinent rescue 
information. Rescue sheets contain abbreviated emergency response 
information about a vehicle's construction. Rescue sheets are most 
likely to be referenced first by emergency responders upon arrival 
at the scene of a crash. ERGs contain more information than rescue 
sheets.
---------------------------------------------------------------------------

    NTSB issued recommendations to vehicle manufacturers, first and 
second responder organizations, and NHTSA. NTSB recommended 
manufacturers of electric vehicles to model their emergency response 
guides on International Standards Organization (ISO)-17840 \122\ and 
SAE International recommended practice SAE J2990, ``Hybrid and EV first 
and second responder recommended practice.'' \123\ It recommended 
incorporating vehicle-specific information on (1) extinguishing REESS 
fires, (2) mitigating risk of REESS reignition, (3) mitigating safety 
risks (electric shock and fire) associated with stranded energy during 
emergency response and transport of damaged vehicle, and (4) storing 
damaged electric vehicles.
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    \122\ ISO-17840, ``Road vehicles--Information for first and 
second responders,'' consists of 4 parts: (1) Part 1 (2015): Rescue 
sheet for passenger cars and light commercial vehicles, (2) Part 2 
(2019): Rescue sheet for buses, coaches, and heavy commercial 
vehicles, (3) Part 3 (2019): Emergency response guide template, and 
(4) Part 4 (2018): Propulsion energy identification. https://webstore.ansi.org/standards/iso/iso178402015?gclid=Cj0KCQiAtbqdBhDvARIsAGYnXBMNT9mR9gjsrKxd5kK8dK6V21Ql9bDr8q2OI0fncMQHHpX_D8bQCxAaAhbUEALw_wcB.
    \123\ SAE J2990 provides format and content recommendations for 
emergency response guides and quick reference sheets in accordance 
with ISO 17840. https://www.sae.org/standards/content/j2990/2_202011/.
---------------------------------------------------------------------------

    NTSB recommended to the vehicle manufacturers to follow the 
practices for first and second emergency responders

[[Page 26729]]

available in SAE J2990 \124\ and ISO-17840. SAE J2990 mainly refers to 
the ISO-17840 for the emergency response information. As indicated 
earlier, ISO-17840 is comprised of four parts:
---------------------------------------------------------------------------

    \124\ SAE J2990 recommended practice provides common procedures 
to help protect emergency responders and personnel supporting towing 
and/or recovery, storage, repair, and salvage after an incident has 
occurred with an electric powertrain vehicle.
---------------------------------------------------------------------------

     ISO 17840-1:2022(E) standardizes the content and layout of 
rescue sheets for passenger cars and light commercial vehicles.
     ISO 17840-2:2019(E) standardizes the rescue sheets for 
buses, coaches, and heavy commercial vehicles.
     ISO 17840-3:2019(E) establishes a template and defines the 
general content for manufacturers' emergency response guides for all 
vehicle types--longer documents that give in-depth ``necessary and 
useful information'' about a vehicle for emergency incidents.
     ISO 17840-4:2018 defines the labels and colors used to 
indicate the fuel or energy used to propel a vehicle for both the 
rescue sheets and the ERGs.
    NTSB had two recommendations to NHTSA. The first recommendation was 
to factor the availability of a manufacturer's ERG and its adherence to 
ISO 17840 and J2990 when determining a vehicle's U.S. New Car 
Assessment Program (NCAP) score.\125\ The second recommendation was to 
convene a coalition of stakeholders to continue research and publish 
the results on ways to mitigate or deenergize the stranded energy in 
high-voltage lithium-ion batteries and to reduce the hazards associated 
with thermal runaway resulting from high-speed, high-severity crashes.
---------------------------------------------------------------------------

    \125\ NHTSA's NCAP is a consumer information program that 
evaluates the safety performance of vehicles and provides 
comparative information on new vehicles. NCAP also provides 
consumers with information on the availability of new vehicle safety 
features. This information is provided to assist consumers with 
vehicle purchasing decisions and to encourage safety improvements in 
vehicle design.
---------------------------------------------------------------------------

    NHTSA responded to NTSB by a letter dated April 2, 2021. Among 
other things, the letter said that NHTSA will be addressing risks to 
emergency responders by working directly with the emergency response 
community. The agency explained that NHTSA has partnered with the 
National Fire Protection Association (NFPA) to support the development 
of training to emergency responders on handling and managing fire 
incidents involving alternative fuel vehicles, including electric 
vehicles.\126\ This NPRM is one result from our partnering with NFPA to 
provide emergency response guides to first and second responders.
---------------------------------------------------------------------------

    \126\ https://www.nhtsa.gov/sites/nhtsa.gov/files/2021-12/NHTSA-NTSB-Response-04-02-2021-Stranded-Energy-Lithium-Ion-Batteries-NCAP-Improvements-tag.pdf.
---------------------------------------------------------------------------

    NHTSA worked with other agencies and stakeholders and issued 
interim guidance in support of the development of training for 
emergency responders. In 2012 and 2014, NHTSA provided interim guidance 
to law enforcement, emergency medical services personnel and fire 
departments when encountering electric or hybrid-electric vehicles, to 
reduce the risk of shock hazards and vehicle fires following vehicle 
submersion.\127\ NHTSA also provided separate interim guidance for 
towing and recovery operators and persons operating vehicle storage 
facilities.\128\ NHTSA continues to lead an inter-agency \129\ effort 
to develop updated guidance on best practices and strategies for 
emergency personnel to contain electric vehicle-related hazards from 
field events, such as electric vehicle fires resulting from storm 
surges like those occurring during Hurricane Ian.
---------------------------------------------------------------------------

    \127\ Interim Guidance for Electric and Hybrid-Electric Vehicles 
Equipped with High-Voltage Batteries (located at https://www.nhtsa.gov/sites/nhtsa.gov/files/811575-interimguidehev-hv-batt_lawenforce-ems-firedept-v2.pdf).
    \128\ ``Interim Guidance for Electric and Hybrid-Electric 
Vehicles Equipped with High-Voltage Batteries,'' located at 811576-
interimguidehev-hv-batt_towing-recovery-storage-v2.pdf (nhtsa.gov).
    \129\ U.S. Department of Energy, the United States Fire 
Administration, and the National Fire Protection Association.
---------------------------------------------------------------------------

b. NHTSA Proposal

The Information Must Be Provided
    Current emergency response information is voluntarily filed on an 
NFPA website.\130\ Rather than factoring the availability of ERGs as 
part of NCAP, NHTSA tentatively believes it would be more effective to 
address risks to emergency responders by directly requiring the 
standardized information. The information would be available and 
understandable to first and second responders so they can refer quickly 
and easily to identify pertinent vehicle-specific rescue information at 
the scene of the crash or fire event, and respond to the emergency 
quickly, effectively, and safely.
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    \130\ https://www.nfpa.org/Training-and-Events/By-topic/Alternative-Fuel-Vehicle-Safety-Training/Emergency-Response-Guides.
---------------------------------------------------------------------------

The Information Must Be Standardized
    To improve the ease and flow of information and, ultimately, the 
safety of persons involved, NHTSA is proposing a requirement that 
vehicle manufacturers submit the emergency response information to 
NHTSA in a standardized format. Currently, the ERGs and rescue sheets 
for alternative fuel vehicles available on the NFPA website is not in a 
standardized format.\131\ The NTSB report indicated that a standardized 
format for ERGs would enhance emergency response as well as protect 
first and second responders. NHTSA tentatively believes this NPRM's 
proposed standardization requirement would make the information more 
understandable and would be another means that would help reduce 
response times and the safety risks to emergency responders.
---------------------------------------------------------------------------

    \131\ https://www.nfpa.org/Training-and-Events/By-topic/Alternative-Fuel-Vehicle-Safety-Training/Emergency-Response-Guides.
---------------------------------------------------------------------------

    Proposed FMVSS No. 305a would require that the rescue sheets must 
follow the layout and format in ISO-17840-1:2022(E) (for vehicles with 
a GVWR less than or equal to 4,536 kg (10,000 lb)) and the format in 
ISO-17840-2:2019(E) (for vehicles with a GVWR greater than 4,536 kg 
(10,000 lb)). ERGs must follow the template layout and format of ISO-
17840-3:2019(E) and provide in-depth information linked and aligned to 
the corresponding rescue sheet to support the quick and safe action of 
emergency responders. The ERGs must also provide in-depth information 
related to electric vehicle fire, submersion, leakage of fluids, 
towing, transportation, and storage.
    NHTSA seeks comment on the proposed format and layout of rescue 
sheets and ERGs in accordance with the different parts of ISO-17840. 
Are there main features of ISO-17840 that should be considered instead 
of referring to specific versions of the ISO-17840 parts? Are there 
specific features not included in ISO-17840 that would further enhance 
first and second responders' operations?
The Information Must Be Vehicle-Specific
    NHTSA tentatively believes that, due to varying electric vehicle 
design and development, emergency response information must be vehicle-
specific. Currently, the ERGs and rescue sheets on the NFPA website are 
not available for all vehicle makes, models, and model years. NHTSA 
tentatively believes that the information is of limited value because 
of this limited availability. The agency tentatively believes that 
requiring information on all vehicles is necessary to best reduce 
response times and the safety risks to emergency responders.

[[Page 26730]]

The Information Must Be Submitted to NHTSA
    NHTSA tentatively believes that easy access to both short and long 
forms of emergency response information are essential to address the 
risk of emergency responders. Therefore, as part of this NPRM and the 
NHTSA's battery safety initiative,\132\ NHTSA is proposing a provision 
in FMVSS No. 305a that would require vehicle manufacturers to submit 
electronic versions of ERGs and rescue sheets for all vehicles to which 
FMVSS No. 305a applies, prior to certification of the vehicle, so that 
they are available in a centralized location on NHTSA's website. The 
rationale of submission prior to certification is to ensure the 
pertinent information for first and second responders are available by 
the time the vehicles are placed on public roads and potentially 
involved in emergencies. The intent is for both the ERGs and rescue 
sheets to be stored and maintained at a centralized web location 
(within NHTSA.gov), so that they are always easily and quickly 
accessible to all first and second responders.
---------------------------------------------------------------------------

    \132\ https://www.nhtsa.gov/battery-safety-initiative.
---------------------------------------------------------------------------

Other Issues Presented for Comment
     To align with NHTSA's intent to have both ERGs and rescue 
sheets accessible in a centralized NHTSA web location, NHTSA would like 
to migrate the ERGs currently on the NFPA website to NHTSA's website. 
NHTSA requests comments on whether electric vehicle ERGs and rescue 
sheets that were previously hosted on the NFPA website should be 
included in NHTSA's centralized web location.
     NHTSA also requests comments on whether the requirement 
described in this section for ERGs and rescue sheets would be better 
placed in a general agency regulation than in proposed FMVSS No. 305a. 
NHTSA discusses this issue at length in section VI. of this preamble 
regarding documentation requirements pertaining to REESS safety risks 
and risk mitigation strategies identified by manufacturers. NHTSA 
requests comments on the pros and cons of having the ERGs and rescue 
sheet requirements in a regulation rather than in FMVSS No. 305a. 
Comments are requested on the pros and cons of placing the requirement 
for providing ERG and rescue sheets to NHTSA to be in a regulation 
rather than in FMVSS No. 305a.

VI. Request for Comment on Placing the Emergency Response Information 
and Documentation Requirements in a Regulation Rather Than in FMVSS No. 
305a

    NHTSA requests comments on whether the proposed emergency response 
information requirements would be better placed in a general agency 
regulation than in proposed FMVSS No. 305a, given that the 
documentation specifications are more akin to a disclosure requirement 
(disclosing information to NHTSA) than a performance test or a consumer 
safety information requirement.
    NHTSA regulates motor vehicle safety under many grants of 
authority. For example, one is that NHTSA is authorized by the Vehicle 
Safety Act to issue FMVSS; a typical FMVSS specifies minimum 
performance requirements and may also include provisions requiring 
manufacturers to provide consumers safety information on properly using 
a safety system or item of equipment. Another is that the Vehicle 
Safety Act authorizes NHTSA to require manufacturers to retain certain 
records and/or make information available to NHTSA. Section 30166 of 
the Act provides NHTSA the ability to request and inspect manufacturer 
records that are necessary to enforce the prescribed regulations. NHTSA 
is also authorized by delegation to issue regulations to carry out the 
agency's duties of ensuring vehicle safety.\133\ Documentation 
requirements would be authorized under these authorities.
---------------------------------------------------------------------------

    \133\ 49 U.S.C. 322(a). This provision states that the Secretary 
of Transportation may prescribe regulations to carry out the duties 
and powers of the Secretary. The authority to implement the Vehicle 
Safety Act has been delegated to NHTSA.
---------------------------------------------------------------------------

    However, NHTSA is mindful that the mechanisms for enforcing a 
failure to meet a documentation requirement could differ depending on 
whether the requirement is in an FMVSS or not. Section 30118 of the 
Vehicle Safety Act (49 U.S.C. 30118) provides that whenever the 
Secretary of Transportation (NHTSA by delegation) determines that a 
vehicle does not comply with an FMVSS, NHTSA (by delegation) must 
require the vehicle's manufacturer to notify the owners, purchasers and 
dealers of the vehicle or equipment of the noncompliance and remedy the 
noncompliance. There is an exception to the recall requirement in 
section 30120(h) which authorizes NHTSA to exempt noncompliances from 
recall provisions based on a demonstration that the noncompliance is 
inconsequential to safety. In the case of a violation of a disclosure 
requirement in a regulation other than an FMVSS, the manufacturer could 
be subject to injunctive remedies and/or civil penalties,\134\ but 
would not be subject to the recall notification and remedy provision 
described above. NHTSA requests comments on the pros and cons of 
placing the proposed emergency response information requirement in a 
regulation rather than in FMVSS No. 305a.
---------------------------------------------------------------------------

    \134\ See, e.g., 49 U.S.C. 30165.
---------------------------------------------------------------------------

    NHTSA also seeks comments on whether the proposed risk mitigation 
documentation requirements would be better placed in a general agency 
regulation. This NPRM proposes manufacturers to document and submit 
information, upon request, describing identified safety risks, risk 
mitigation strategies, and validation of those strategies. NHTSA has 
similar documentation requirements in FMVSS No. 126, ``Electronic 
stability control systems for light vehicles'' \135\ and FMVSS No. 226, 
``Ejection Mitigation.'' \136\ NHTSA requests comments on the pros and 
cons of placing the proposed risk mitigation documentation requirement 
in a regulation rather than in FMVSS No. 305a.
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    \135\ 49 CFR 571.126 S5.6.
    \136\ 49 CFR 571.226 S4.2.4.
---------------------------------------------------------------------------

VII. Proposed Compliance Dates

    The proposed compliance dates are as follows.
    1. Regarding the proposed requirements other than the emergency 
response information to assist first and second responders, the 
compliance date would be two years after the publication of the final 
rule in the Federal Register. Small-volume manufacturers, final-stage 
manufacturers, and alterers would be provided an additional year to 
comply with the final rule beyond the two-year date identified 
above.\137\ We propose to permit optional early compliance with the 
final rule.
---------------------------------------------------------------------------

    \137\ 49 CFR 571.8(b).
---------------------------------------------------------------------------

    Under Sec.  30111(d) of the Safety Act, a standard may not become 
effective before the 180th day after the standard is prescribed or 
later than one year after it is prescribed, unless NHTSA finds, for 
good cause shown, that a different effective date is in the public 
interest and publishes the reasons for the finding. NHTSA has 
tentatively determined that a 2-year compliance period is in the public 
interest because all vehicle manufacturers need to gain familiarity 
with the proposed REESS requirements. There is already widespread 
conformance to the requirements so the 2-year period ought

[[Page 26731]]

to provide sufficient time, but some manufacturers may need time to 
assess fleet performance, review their risk management procedures and 
document their mitigation strategies. Further, heavy vehicle 
manufacturers would be newly subject to electric system integrity 
requirements having not been subject to existing FMVSS No. 305. They 
will need time to assess their vehicles' conformance to FMVSS No. 305a 
requirements, implement appropriate design and production changes, and 
assess and document risk mitigation strategies.
    2. Regarding requirements to provide emergency response information 
to assist first and second responders, the proposed compliance date is 
one year after publication of the final rule. Small-volume 
manufacturers, final-stage manufacturers, and alterers would be 
provided an additional year to comply with the final rule. Optional 
early compliance would be permitted. NHTSA believes the 1-year 
compliance date for this proposed requirement is long enough for 
manufacturers to provide the information to NHTSA in the required 
format. They are already providing the information voluntarily to the 
NFPA. The agency would like to provide the information on NHTSA's 
website as soon as possible. If manufacturers provide the information 
in a year, NHTSA can begin the process of posting the information 
shortly thereafter.

VIII. Rulemaking Analyses and Notices

Executive Order 12866, Executive Order 14094, Executive Order 13563, 
and DOT Order 2100.6A

    NHTSA has considered the impact of this rulemaking action under 
Executive Orders 12866, 14094, and 13563 and DOT Order 2100.6A. This 
action was not reviewed by the Office of Management and Budget under 
E.O. 12866.
    This NPRM proposes to update FMVSS No. 305 to incorporate the 
electrical safety requirements in GTR No. 20 and issue FMVSS No. 305a 
with the incorporated requirements. Most of GTR No. 20 has already been 
adopted into FMVSS No. 305; this NPRM proposes to complete the process 
by expanding FMVSS No. 305's applicability to heavy vehicles and by 
adopting the GTR's requirements for the REESS. Since there is 
widespread conformance with the requirements that would apply to 
existing vehicles, we anticipate no costs or benefits associated with 
this rulemaking.
    This NPRM also proposes a requirement that electric vehicle 
manufacturers submit standardized emergency response information to a 
NHTSA central depository, to assist first and second responders. A 
comprehensive list of pertinent vehicle specific rescue information at 
a central location will enable first and second responders to respond 
to emergencies as quickly and safely as possible. Currently, electric 
vehicle manufacturers voluntarily upload emergency response information 
to the National Fire Protection Association's training site, so 
manufacturers are already providing vehicle specific emergency response 
information. With this proposed rule, manufacturers would submit ERGs 
and rescue sheets to NHTSA instead. We anticipate no additional costs 
by the manufacturers.

Regulatory Flexibility Act

    NHTSA has considered the effects of this NPRM under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq., as amended by the Small Business 
Regulatory Enforcement Fairness Act (SBREFA) of 1996). I certify that 
this NPRM, if promulgated, would not have a significant economic impact 
on a substantial number of small entities. NHTSA is aware of 3 small 
manufacturers of light and heavy electric vehicles. NHTSA believes that 
this proposed rule would not have a significant economic impact on 
these manufacturers for the following reasons. First, small 
manufacturers of light electric vehicles that might be affected by this 
NPRM are already subject to the electric vehicle safety requirements of 
FMVSS No. 305 and have been certifying compliance to the standard for 
years. They are familiar with FMVSS requirements for electric vehicle 
safety, know how to assess the conformance of their vehicles with the 
requirements, and know how to certify their vehicles to the FMVSS. The 
new proposed requirements for the REESS are manageable because the 
overcharge, over-discharge, over-current, over-temperature, and 
external short-circuit tests are non-destructive tests and can be 
conducted in serial order. The documentation requirements for safety 
risk mitigation associated with charging and discharging during cold 
temperature, safety risk mitigation associated with an internal short-
circuit in a single cell of a REESS, and warning in the event of a 
malfunction of the vehicle controls that manage REESS safe operation 
are not design restrictive and add minimal cost. The documentation 
requirements simply ask manufacturers to describe to NHTSA how they 
have assessed certain safety risks and mitigated them.
    Second, there already is widespread voluntarily compliance by the 
manufacturers with GTR No. 20, which is also aligned with industry 
standards. Therefore, there will be only a minor economic impact.
    Finally, although the final certification would be made by the 
manufacturer, this proposal would allow one additional year for small 
volume manufacturers, final-stage manufacturers and alterers to comply 
with a final rule. This approach is similar to the approach NHTSA has 
taken in other rulemakings in recognition of manufacturing differences 
between larger and smaller manufacturers. NHTSA anticipates that EV 
components meeting FMVSS No. 305a would be developed by vehicle 
designers and suppliers and integrated into the fleets of larger 
vehicle manufacturers first, before small manufacturers. This NPRM 
recognizes this and proposes to provide smaller manufacturers 
flexibility, so they have time to obtain the equipment and work with 
the suppliers after the demands of the larger manufacturers are met.
    This NPRM would apply proposed FMVSS No. 305a to heavy vehicles, so 
this NPRM would also affect manufacturers of vehicles of over 4,536 kg 
(10,000 lb) GVWR, some of which may be final-stage manufacturers.\138\ 
According to the U.S. Census, there are 570 small businesses in body 
manufacturing for light, medium, and heavy-duty classes. This proposal 
could affect a substantial number of final stage manufacturers that are 
small businesses. However, it is NHTSA's understanding that these small 
entities rarely make modifications to a vehicle's REESS system and 
instead rely upon the pass-through certification provided by the first-
stage manufacturer, which is not typically a small business. The same 
is true for alterers, which are manufacturers that obtain and alter a 
complete vehicle prior to the vehicle's first sale to a consumer.\139\ 
Furthermore, even if the final-stage manufacturer or alterer must make 
the certification independently, as explained above this

[[Page 26732]]

certification responsibility is manageable. The proposed requirements 
do not involve crash testing (except for heavy school buses, as 
discussed below), and conformance with the requirements can be assessed 
relatively simply in a laboratory setting. And finally, this proposal 
would further accommodate final-stage manufacturers and alterers by 
providing them an additional year before compliance is required.\140\ 
For the reasons above, NHTSA does not believe that the economic impacts 
of this proposal on small entities would be significant.
---------------------------------------------------------------------------

    \138\ Final-stage manufacturers produce vehicles by obtaining an 
incomplete vehicle (comprising the chassis and other associated 
parts) manufactured by an incomplete vehicle manufacturer, which is 
typically a large manufacturer. The final-stage manufacturer 
produces a vehicle by installing the vehicle body on the incomplete 
vehicle. The final-stage manufacturer typically certifies a complete 
vehicle by staying within manufacturing instructions provided by the 
incomplete vehicle manufacturer.
    \139\ Alterers certify that the vehicle was altered by them and 
as altered conforms to all applicable FMVSS, bumper, and theft 
prevention standards affected by the alteration.
    \140\ See 49 CFR 571.8(b).
---------------------------------------------------------------------------

    With regard to the proposed crash test requirement for small 
manufacturers of heavy school buses, the additional requirement is for 
heavy school buses with high voltage electric propulsion systems to 
meet post-crash electrical safety requirements when impacted by the 
moving contoured barrier specified in FMVSS No. 301. This requirement 
does not require additional crash testing and aligns the applicability 
of FMVSS No. 305a with that of FMVSS Nos. 301 and 303. Per FMVSS No. 
301 and FMVSS No. 303, heavy school buses (school buses with a GVWR 
greater than 4,536 kg) using conventional fuel or compressed natural 
gas for propulsion are required to maintain fuel system integrity in a 
crash test where the moving contoured barrier specified in FMVSS No. 
301 traveling at any speed up to 48 km/h impacts the school bus at any 
point and angle. These requirements ensure post-crash safety to 
maintain the current high safety standards for school buses. Finally, 
this proposal would accommodate small manufacturers and final stage 
manufacturers of heavy school buses by providing them an additional 
year before compliance is required. For the reasons above, NHTSA does 
not believe that the economic impacts of this proposal on small 
entities would be significant.

National Environmental Policy Act

    NHTSA has analyzed this rulemaking action for the purposes of the 
National Environmental Policy Act (42 U.S.C. 4321 et seq.), as amended. 
The agency has determined that implementation of this action will not 
have an adverse impact on the quality of the human environment. As 
described earlier, the proposal includes the current requirements in 
FMVSS No. 305 but would also expand the applicability of the standard 
to heavy vehicles (vehicles with a gross vehicle weight rating (GVWR) 
greater than 4,536 kilograms (kg) (10,000 lb)), add requirements to 
mitigate post-crash vehicle fires, add an optional method for assessing 
electrical safety for capacitors included in the electric powertrain, 
and include crash test and post-crash safety requirements for school 
buses with a GVWR greater than 4,536 kg (10,000 lb). The proposal would 
align the standard with electrical safety requirements in the Global 
Technical Regulation (GTR) No. 20, ``Electric Vehicle Safety,'' which 
has been formally adopted by the UN World Forum for Harmonization of 
Vehicle Regulations. The proposal, with expanded applicability and 
additional requirements and test procedures, would enable future 
updates to the standard as battery technologies and charging systems 
continue to evolve.
    NHTSA expects the changes to new and existing vehicles to be 
minimal, and mitigating the hazards associated with electric shock 
during parked conditions, active drive-possible modes, external 
charging, and post-crash events, as well as risks associated with 
hazardous conditions resulting from battery fires and emissions, would 
result in a public health and safety benefit. For these reasons, the 
agency has determined that implementation of this action will not have 
any adverse impact on the quality of the human environment.

Executive Order 13132 (Federalism)

    NHTSA has examined this proposed rule pursuant to Executive Order 
13132 (64 FR 43255; Aug. 10, 1999) and concluded that no additional 
consultation with States, local governments, or their representatives 
is mandated beyond the rulemaking process. The agency has concluded 
that the proposal does not have sufficient federalism implications to 
warrant consultation with State and local officials or the preparation 
of a federalism summary impact statement. The proposal does not have 
``substantial direct effects on the States, on the relationship between 
the national government and the States, or on the distribution of power 
and responsibilities among the various levels of government.''
    NHTSA rules can have preemptive effect in two ways. First, the 
National Traffic and Motor Vehicle Safety Act contains an express 
preemption provision: When a motor vehicle safety standard is in effect 
under this chapter, a State or a political subdivision of a State may 
prescribe or continue in effect a standard applicable to the same 
aspect of performance of a motor vehicle or motor vehicle equipment 
only if the standard is identical to the standard prescribed under this 
chapter. 49 U.S.C. 30103(b)(1). It is this statutory command that 
preempts any non-identical State legislative and administrative law 
address the same aspect of performance.
    The express preemption provision described above is subject to a 
savings clause under which ``[c]compliance with a motor vehicle safety 
standard prescribed under this chapter does not exempt a person from 
liability at common law.'' 49 U.S.C. 30103(e). Pursuant to this 
provision, State common law tort causes of action against motor vehicle 
manufacturers that might otherwise be preempted by the express 
preemption provision are generally preserved. However, the Supreme 
Court has recognized the possibility, in some instances, of implied 
preemption of State common law tort causes of action by virtue of 
NHTSA's rules--even if not expressly preempted.
    This second way that NHTSA rules can preempt is dependent upon the 
existence of an actual conflict between an FMVSS and the higher 
standard that would effectively be imposed on motor vehicle 
manufacturers if someone obtained a State common law tort judgment 
against the manufacturer--notwithstanding the manufacturer's compliance 
with the NHTSA standard. Because most NHTSA standards established by an 
FMVSS are minimum standards, a State common law tort cause of action 
that seeks to impose a higher standard on motor vehicle manufacturers 
will generally not be preempted. However, if and when such a conflict 
does exist--for example, when the standard at issue is both a minimum 
and a maximum standard--the State common law tort cause of action is 
impliedly preempted. See Geier v. American Honda Motor Co., 529 U.S. 
861 (2000).
    Pursuant to Executive Order 13132, NHTSA has considered whether 
this proposed rule could or should preempt State common law causes of 
action. The agency's ability to announce its conclusion regarding the 
preemptive effect of one of its rules reduces the likelihood that 
preemption will be an issue in any subsequent tort litigation.
    To this end, the agency has examined the nature (e.g., the language 
and structure of the regulatory text) and objectives of this proposed 
rule and does not foresee any potential State requirements that might 
conflict with it. NHTSA does not intend that this proposed rule preempt 
state tort law that would effectively impose a higher standard on motor 
vehicle manufacturers than that established by this proposed rule. 
Establishment of a higher standard by means of State tort law would not 
conflict with the

[[Page 26733]]

standards proposed in this NPRM. Without any conflict, there could not 
be any implied preemption of a State common law tort cause of action.

Executive Order 12988 (Civil Justice Reform)

    With respect to the review of the promulgation of a new regulation, 
section 3(b) of Executive Order 12988, ``Civil Justice Reform'' (61 FR 
4729; Feb. 7, 1996), requires that Executive agencies make every 
reasonable effort to ensure that the regulation: (1) Clearly specifies 
the preemptive effect; (2) clearly specifies the effect on existing 
Federal law or regulation; (3) provides a clear legal standard for 
affected conduct, while promoting simplification and burden reduction; 
(4) clearly specifies the retroactive effect, if any; (5) specifies 
whether administrative proceedings are to be required before parties 
file suit in court; (6) adequately defines key terms; and (7) addresses 
other important issues affecting clarity and general draftsmanship 
under any guidelines issued by the Attorney General. This document is 
consistent with that requirement.
    Pursuant to this Order, NHTSA notes as follows. The issue of 
preemption is discussed above. NHTSA notes further that there is no 
requirement that individuals submit a petition for reconsideration or 
pursue other administrative proceedings before they may file suit in 
court.

Privacy Act

    Please note that anyone is able to search the electronic form of 
all comments received into any of our dockets by the name of the 
individual submitting the comment (or signing the comment, if submitted 
on behalf of an association, business, labor union, etc.). You may 
review DOT's complete Privacy Act Statement in the Federal Register 
published on April 11, 2000 (65 FR 19477-78), or online at http://www.dot.gov/privacy.html.

Paperwork Reduction Act

    Under the procedures established by the Paperwork Reduction Act of 
1995 (PRA) (44 U.S.C. 3501, et. seq.), Federal agencies must obtain 
approval from the OMB for each collection of information they conduct, 
sponsor, or require through regulations. A person is not required to 
respond to a collection of information by a Federal agency unless the 
collection displays a valid OMB control number. The Information 
Collection Request (ICR) for the proposed new information collection 
described below have been forwarded to OMB for review and comment. In 
compliance with these requirements, NHTSA asks for public comments on 
the following proposed collections of information for which the agency 
is seeking approval from OMB.
    There are two types of collection of information that are part of 
the proposed FMVSS No. 305a requirements: (1) Electric Vehicles: Rescue 
Sheets and Emergency Response Guides and (2) Electric Vehicles: REESS 
Thermal Propagation Safety Risk Analysis and Mitigation Documentation.
    Title: FMVSS No. 305a Electric Vehicle Emergency Response 
Information and Risk Mitigation Documentation.
    OMB Control Number: New.
    Form Number: N/A.
    Type of Request: Approval of a new collection.
    Type of Review Requested: Regular.
    Requested Expiration Date of Approval: 3 years from the date of 
approval.
    Summary of the Collection of Information:
    FMVSS No. 305a proposes electric vehicle (EV) requirements for 
protection from harmful electric shock, fire, explosion, and gas 
venting during normal vehicle operation and during and after a crash. 
As part of the proposed requirements, there are two types of 
information collection that would apply to all electric vehicle (EV) 
manufacturers. First, before certification, each manufacturer will be 
required to submit emergency response information, including rescue 
sheets and emergency response guides (ERGs) for each vehicle make, 
model, and model year, so they are available in a centralized location 
on NHTSA's website. The information would then be readily available for 
first and second responders so they can easily identify pertinent 
vehicle-specific rescue information at the scene of a vehicle crash or 
fire event, and respond to the emergency quickly, effectively, and 
safely.
    Second, each electric vehicle model will be required to meet three 
proposed documentation requirements and manufacturers will be required 
to submit to NHTSA, upon request, documentation demonstrating risk 
mitigation for certain safety hazards. The documentation must describe 
safety risk mitigation associated with charging and discharging during 
cold temperature, safety risk mitigation associated with an internal 
short-circuit in a single cell of a REESS, and warning in the event of 
a malfunction of the vehicle controls that manage REESS safe operation.
    Description of the Need for the Information and Proposed Use of the 
Information:
    First responders need detailed information pertaining to an EV's 
electrical system layout in order to safely work around the vehicle and 
extricate injured passengers. Access to vehicle-specific information in 
a clear, standardized format help mitigate the safety risks of high 
voltage components and stranded energy in the Rechargeable Electrical 
Energy Storage System (REESS). The purpose of the requirement is to 
make this information readily available for first and second responders 
for their safe handling of the vehicle in emergencies and for towing 
and storing operations. Rescue sheets and ERGs communicate vehicle-
specific information related to fire, submersion, and towing, as well 
as the location of components in the vehicle that may expose the 
vehicle occupants or rescue personnel to risks. The information is 
presented in a specific format with color-coded sections in a specific 
order to help first and second responders quickly identify pertinent 
rescue information. Rescue sheets contain abbreviated emergency 
response information about a vehicle's construction. Rescue sheets are 
most likely to be referenced first by emergency responders upon arrival 
at the scene of a crash. ERGs contain more information than rescue 
sheets.
    Current emergency response information is voluntarily filed on the 
National Fire Protection Association (NFPA) website, but they are not 
in standardized format. The uploaded rescue sheets and ERGs would be 
standardized in layout and format and be publicly available at NHTSA's 
website for quick access.
    There are currently no objective test procedures to evaluate REESS 
mitigation of certain safety risks in a manner that is not design 
restrictive. Until test procedures and performance criteria can be 
developed for all vehicle powertrain architectures, the proposed FMVSS 
No. 305a would require manufacturers to compile and meet three of the 
proposed documentation requirements and submit documentation to NHTSA, 
if requested, that identifies all known safety hazards, the risk 
mitigation strategies for the safety hazards, and, if applicable, 
describe how they provide a warning to address a safety hazard. Given 
the variation of battery design and design-specific risk mitigation 
systems, the documentation is a means for manufacturers to show that 
they have identified and demonstrated safety risk mitigation 
strategies, and for NHTSA to

[[Page 26734]]

learn of and oversee the safety hazards. This approach is battery 
technology neutral, not design restrictive, and is intended to evolve 
over time as battery technologies continue to rapidly evolve. These 
proposed documentation requirements would address: (a) safety risk 
mitigation associated with charging and discharging during low 
temperature; (b) the safety risks from thermal propagation in the event 
of SCTR due to an internal short-circuit of a single cell; and (c) 
providing a warning if there is a malfunction of vehicle controls that 
manage REESS safe operation.
    Affected Public: Vehicle manufacturers.
    Frequency: Emergency response information: as needed upon 
certification; Risk mitigation documentation: annually for 
recordkeeping.
    Number of Responses: It is anticipated that an estimated 205 rescue 
sheets and ERGs will be submitted each year and all 205 unique models 
would be compiling and maintaining the required documentation annually.
    Electric vehicle models encompass battery-powered electric vehicle, 
plug-in hybrid electric vehicle, hybrid electric vehicle, and fuel cell 
electric vehicle models. The combined number of electric vehicle models 
is estimated to be 205 unique models each year. Upon certification, a 
total of 205 rescue sheets and ERGs for all unique models will be 
submitted. Out of the 205 EV models, about 51 (25% of EV models) likely 
already have rescue sheets and ERGs that conform to the proposed 
requirements. The number of new rescue sheets and ERGs that would be 
required to be compiled and submitted to NHTSA before certification is 
estimated to be 51 (25% of the combined EV models sold each year). 
NHTSA also anticipates updates to existing or previously submitted 
rescue sheets and ERGs for some vehicle models. Updates may be 
necessary when a vehicle model changes between model years or there are 
revisions to an existing model's emergency response information. It is 
estimated that approximately 103 (50% of the 205 annual electric 
vehicle models) electric vehicle models sold each year would have 
updated or revised rescue sheets and ERGs. Because rescue sheets and 
emergency response guides often cover several model years, the 
percentage of models that would be needing new or updates to existing 
or previously submitted rescue sheets and ERGs are likely to decrease 
after the second year of the effective date.
    Estimated Total Annual Burden Hours: 16,241 hours (2,506 hours for 
emergency response information and 13,735 hours for risk mitigation 
documentation).
    For vehicle models that already have rescue sheets and ERGs that 
conform to the proposed requirements, it is estimated to take 0.25 hour 
to submit the required emergency response information to NHTSA's 
website. The estimated burden hours for the 51 EV models to submit 
their conformed rescue sheets and ERGs is 13 hours (0.25 hour/model x 
51 models).
    For each new electric vehicle model, it is anticipated that it will 
take approximately 36 hours to complete the vehicle-specific rescue 
sheet and emergency response guide following the required format and 
layout provided in ISO-17840-1:2022, ISO-17840-2:2019, and ISO-17840-
3:2019. The estimated total annual burden hours for new rescue sheets 
and emergency response guides is 1,849 hours (36.25 hours/model x 51 
models).
    It is anticipated that it will take approximately 6 hours to update 
the rescue sheet and emergency response guide for a vehicle model. The 
estimated total annual burden hours for updated rescue sheets and 
emergency response guides is 644 hours (6.25 hours/model x 103 models). 
The estimated total annual burden hours is 2,506 hours.
    For each vehicle model, vehicle manufacturers will need an 
estimated 67 hours to complete the three documentation requirements (17 
hours to complete the documentation for low temperature operation 
safety, 17 hours for the documentation about warning in the event of 
operational failure of REESS vehicle controls, and 33 hours for the 
documentation covering thermal runaway due to internal short in a 
single cell of the REESS). After the proposed rule's effective date, 
all 205 vehicle models are expected to compile the necessary 
information to meet the three proposed documentation requirements. The 
total estimated annual burden hours for the three documentation 
requirements is an estimate of 13,735 hours (205 vehicle models x 67 
hours).
    Estimated Total Annual Burden Cost: $1,027,381 ($157,543 for 
emergency response information and $869,838 for risk mitigation 
documentation).
    The preparation of information is anticipated to be done by a 
technical writer. The U.S. Bureau of Labor Statistics (BLS) estimates 
the mean hourly wage for technical writers in the motor vehicle 
manufacturing industry as $44.71.\141\ The BLS estimates that private 
industry workers' wages account for 70.6% of a worker's total 
compensation.\142\ Therefore, NHTSA estimates the hourly labor costs to 
be $63.33 ($44.71/hour/70.6%). The submission of information is 
anticipated to be done by an administrative professional. The U.S. BLS 
estimates the mean hourly wage for administrative professional in the 
motor vehicle manufacturing industry is $29.36.\143\ Therefore, NHTSA 
estimates the hourly labor costs for submission to be $41.59 ($29.36/
hour/70.6%).
---------------------------------------------------------------------------

    \141\ See May 2022 National Industry-Specific Occupational 
Employment and Wage Estimates, NAICS 336100--Motor Vehicle 
Manufacturing, available at https://www.bls.gov/oes/current/naics4_336100.htm (accessed February 29, 2024).
    \142\ See Table 1. Employer Costs for Employee Compensation by 
ownership (Sept. 2023), available at Table 1. By ownership--2023 Q03 
Results (bls.gov).
    \143\ See May 2022 National Industry-Specific Occupational 
Employment and Wage Estimates, NAICS 336100--Motor Vehicle 
Manufacturing, available at https://www.bls.gov/oes/current/naics4_336100.htm (accessed February 29, 2024).
---------------------------------------------------------------------------

    These estimates produce an annual cost burden to manufacturers of 
$116,804 (51 models x ((36 hours x $63.33) + (0.25 hour x $41.59)) for 
generating and submitting the emergency response information 
documentation for new models, $40,209 (103 models x ((6 hours x $63.33) 
+ (0.25 hour x $41.59)) for updating and submitting the documentation, 
and $530 (51 models x (0.25 hour x $41.59)) for those EV models that 
already conform to the proposed requirements for submission. The total 
labor cost to prepare and submit the emergency response information 
documentation to NHTSA's website is estimated to be $157,543 annually.
    Because rescue sheets and emergency response guides often cover 
several model years, the percentage of models that would be needing new 
or updates to existing or previously submitted rescue sheets and ERGs 
each year are likely to decrease in subsequent years. This would result 
in a reduction in annual total burden hours and annual total burden 
costs.
    The preparation of the risk mitigation documentation is also 
anticipated to be done by a technical writer. The total cost burden for 
manufacturers for compiling and record keeping the three documentation 
packets would be $869,838 (205 vehicle models x (67 hours x $63.33)).
    The estimated total annual burden hours to manufacturers for the 
proposed FMVSS No. 305a emergency response information and 
documentation requirements would be 16,241 hours.

[[Page 26735]]

The estimated total annual cost burden to manufacturers for the 
proposed FMVSS No. 305a emergency response information and 
documentation requirements would be $1,027,381.
    Public Comments Invited: You are asked to comment on any aspects of 
this information collection, including (a) whether the proposed 
collection of information is necessary for the proper performance of 
the functions of the Department, including whether the information will 
have practical utility; (b) the accuracy of the Department's estimate 
of the burden of the proposed information collection; (c) ways to 
enhance the quality, utility and clarity of the information to be 
collected; and (d) ways to minimize the burden of the collection of 
information on respondents, including the use of automated collection 
techniques or other forms of information technology.
    Please submit any comments, identified by the docket number in the 
heading of this document, by the methods described in the ADDRESSES 
section of this document to NHTSA and OMB. Although comments may be 
submitted during the entire comment period, comments received within 30 
days of publication are most useful.

National Technology Transfer and Advancement Act

    Section 12(d) of the National Technology Transfer and Advancement 
Act of 1995 (NTTAA), Public Law 104-113, as amended by Public Law 107-
107 (15 U.S.C. 272), directs the agency to evaluate and use voluntary 
consensus standards in its regulatory activities unless doing so would 
be inconsistent with applicable law or is otherwise impractical. 
Voluntary consensus standards are technical standards (e.g., materials 
specifications, test methods, sampling procedures, and business 
practices) that are developed or adopted by voluntary consensus 
standards bodies, such as the Society of Automotive Engineers (SAE). 
The NTTAA directs us to provide Congress (through OMB) with 
explanations when the agency decides not to use available and 
potentially applicable voluntary consensus standards.
    This proposal to adopt GTR No. 20 is consistent with the goals of 
the NTTAA. This NPRM proposes to adopt a global consensus standard. The 
GTR was developed by a global regulatory body and is designed to 
increase global harmonization of differing vehicle standards. The GTR 
leverages the expertise of governments in developing a vehicle standard 
to increase electric vehicle safety, including the performance of the 
REESS. NHTSA's consideration of GTR No. 20 accords with the principles 
of NTTAA as NHTSA's consideration of an established, proven global 
technical regulation has reduced the need for NHTSA to expend 
significant agency resources on the same safety need addressed by GTR 
No. 20.

Unfunded Mandates Reform Act

    Section 202 of the Unfunded Mandates Reform Act of 1995 (UMRA), 
Public Law 104-4, requires Federal agencies to prepare a written 
assessment of the costs, benefits, and other effects of proposed or 
final rules that include a Federal mandate likely to result in the 
expenditure by State, local, or tribal governments, in the aggregate, 
or by the private sector, of more than $100 million annually (adjusted 
for inflation with base year of 1995). Adjusting this amount by the 
implicit gross domestic product price deflator for the year 2022 
results in $177 million (111.416/75.324 = 1.48). This NPRM would not 
result in a cost of $177 million or more to either State, local, or 
tribal governments, in the aggregate, or the private sector. Thus, this 
NPRM is not subject to the requirements of sections 202 of the UMRA.

Executive Order 13609 (Promoting Regulatory Cooperation)

    The policy statement in section 1 of Executive Order 13609 
provides, in part: The regulatory approaches taken by foreign 
governments may differ from those taken by U.S. regulatory agencies to 
address similar issues. In some cases, the differences between the 
regulatory approaches of U.S. agencies and those of their foreign 
counterparts might not be necessary and might impair the ability of 
American businesses to export and compete internationally. In meeting 
shared challenges involving health, safety, labor, security, 
environmental, and other issues, international regulatory cooperation 
can identify approaches that are at least as protective as those that 
are or would be adopted in the absence of such cooperation. 
International regulatory cooperation can also reduce, eliminate, or 
prevent unnecessary differences in regulatory requirements.
    The agency participated in the development of GTR No. 20 to 
harmonize the standards of electric vehicle. As a signatory member, 
NHTSA is proposing to incorporate electrical safety requirements and 
options specified in GTR No. 20 into FMVSS No. 305a.

Incorporation by Reference

    Under regulations issued by the Office of the Federal Register (1 
CFR 51.5(a)), an agency must summarize in the preamble of a proposed or 
final rule the material it incorporates by reference and discuss the 
ways the material is reasonably available to interested parties or how 
the agency worked to make materials available to interested parties.
    NHTSA proposes to incorporate by reference three documents into the 
Code of Federal Regulations. The first document is ISO 17840-1:2022 
(E), ``Road vehicles--Information for first and second responders--Part 
1: Rescue sheet for passenger cars and light commercial vehicles.'' ISO 
17840-1:2022(E) standardizes the content and layout of rescue sheets 
for passenger cars and light commercial vehicles.
    The second document is ISO 17840-2:2019(E), ``Road vehicles--
Information for first and second responders--Part 2: Rescue sheet for 
buses, coaches and heavy commercial vehicles.'' ISO 17840-2:2019(E) 
standardizes the rescue sheets for buses, coaches, and heavy commercial 
vehicles.
    The third document is ISO 17840-3:2019(E), ``Road vehicles--
Information for first and second responders--Part 3: Emergency response 
guide template.'' ISO 17840-3:2019(E) establishes a template and 
defines the general content for manufacturers' emergency response 
guides for all vehicle types.
    All three documents would be incorporated by reference solely to 
specify the layout and format of the rescue sheets and emergency 
response guides. The ISO material is available for review at NHTSA and 
is available for purchase from ISO.\144\
---------------------------------------------------------------------------

    \144\ ISO standards may be purchased from the ANSI webstore 
https://webstore.ansi.org/.
---------------------------------------------------------------------------

Severability

    The issue of severability of FMVSSs is addressed in 49 CFR 571.9. 
It provides that if any FMVSS or its application to any person or 
circumstance is held invalid, the remainder of the part and the 
application of that standard to other persons or circumstances is 
unaffected. Comments are requested on the severability of this proposed 
FMVSS.

Regulation Identifier Number

    The Department of Transportation assigns a regulation identifier 
number (RIN) to each regulatory action listed in the Unified Agenda of 
Federal Regulations. The Regulatory Information Service Center 
publishes the Unified Agenda in April and October of each year. You may 
use the RIN contained in

[[Page 26736]]

the heading at the beginning of this document to find this action in 
the Unified Agenda.

Rulemaking Summary, 5 U.S.C. 553(b)(4)

    As required by 5 U.S.C. 553(b)(4), a summary of this rule can be 
found in the Abstract section of the Department's Unified Agenda entry 
for this rulemaking at https://www.reginfo.gov/public/do/eAgendaViewRule?pubId=202304&RIN=2127-AM43.

Plain Language

    Executive Order 12866 requires each agency to write all rules in 
plain language. Application of the principles of plain language 
includes consideration of the following questions:
     Have we organized the material to suit the public's needs?
     Are the requirements in the rule clearly stated?
     Does the rule contain technical language or jargon that 
isn't clear?
     Would a different format (grouping and order of sections, 
use of headings, paragraphing) make the rule easier to understand?
     Would more (but shorter) sections be better?
     Could we improve clarity by adding tables, lists, or 
diagrams?
     What else could we do to make the rule easier to 
understand?
    If you have any responses to these questions, please write to us 
with your views.

IX. Public Participation

How long do I have to submit comments?

    Please see DATES section at the beginning of this document.

How do I prepare and submit comments?

     Your comments must be written in English.
     To ensure that your comments are correctly filed in the 
Docket, please include the Docket Number shown at the beginning of this 
document in your comments.
     Your comments must not be more than 15 pages long. (49 CFR 
553.21). We established this limit to encourage you to write your 
primary comments in a concise fashion. However, you may attach 
necessary additional documents to your comments. There is no limit on 
the length of the attachments.
     If you are submitting comments electronically as a PDF 
(Adobe) File, NHTSA asks that the documents be submitted using the 
Optical Character Recognition (OCR) process, thus allowing NHTSA to 
search and copy certain portions of your submissions. Comments may be 
submitted to the docket electronically by logging onto the Docket 
Management System website at http://www.regulations.gov. Follow the 
online instructions for submitting comments.
     You may also submit two copies of your comments, including 
the attachments, to Docket Management at the address given above under 
ADDRESSES.
    Please note that pursuant to the Data Quality Act, in order for 
substantive data to be relied upon and used by the agency, it must meet 
the information quality standards set forth in the OMB and DOT Data 
Quality Act guidelines. Accordingly, we encourage you to consult the 
guidelines in preparing your comments. OMB's guidelines may be accessed 
at http://www.whitehouse.gov/omb/fedreg/reproducible.html. DOT's 
guidelines may be accessed at http://www.bts.gov/programs/statistical_policy_and_research/data_quality_guidelines.

How can I be sure that my comments were received?

    If you wish Docket Management to notify you upon its receipt of 
your comments, enclose a self-addressed, stamped postcard in the 
envelope containing your comments. Upon receiving your comments, Docket 
Management will return the postcard by mail.

How do I submit confidential business information?

    You should submit a redacted ``public version'' of your comment 
(including redacted versions of any additional documents or 
attachments) to the docket using any of the methods identified under 
ADDRESSES. This ``public version'' of your comment should contain only 
the portions for which no claim of confidential treatment is made and 
from which those portions for which confidential treatment is claimed 
has been redacted. See below for further instructions on how to do 
this.
    You also need to submit a request for confidential treatment 
directly to the Office of Chief Counsel. Requests for confidential 
treatment are governed by 49 CFR part 512. Your request must set forth 
the information specified in Part 512. This includes the materials for 
which confidentiality is being requested (as explained in more detail 
below); supporting information, pursuant to Part 512.8; and a 
certificate, pursuant to Part 512.4(b) and Part 512, Appendix A.
    You are required to submit to the Office of Chief Counsel one 
unredacted ``confidential version'' of the information for which you 
are seeking confidential treatment. Pursuant to Part 512.6, the words 
``ENTIRE PAGE CONFIDENTIAL BUSINESS INFORMATION'' or ``CONFIDENTIAL 
BUSINESS INFORMATION CONTAINED WITHIN BRACKETS'' (as applicable) must 
appear at the top of each page containing information claimed to be 
confidential. In the latter situation, where not all information on the 
page is claimed to be confidential, identify each item of information 
for which confidentiality is requested within brackets: ``[ ].''
    You are also required to submit to the Office of Chief Counsel one 
redacted ``public version'' of the information for which you are 
seeking confidential treatment. Pursuant to Part 512.5(a)(2), the 
redacted ``public version'' should include redactions of any 
information for which you are seeking confidential treatment (i.e., the 
only information that should be unredacted is information for which you 
are not seeking confidential treatment).
    NHTSA is currently treating electronic submission as an acceptable 
method for submitting confidential business information to the agency 
under Part 512. Please do not send a hardcopy of a request for 
confidential treatment to NHTSA's headquarters. The request should be 
sent to Dan Rabinovitz in NHTSA's Office of the Chief Counsel (NCC) at 
[email protected]. You may either submit your request via email 
or request a secure file transfer link. If you are submitting the 
request via email, please also email a courtesy copy of the request to 
K.Helena Sung in NCC at [email protected].

Will the agency consider late comments?

    We will consider all comments that Docket Management receives 
before the close of business on the comment closing date indicated 
above under DATES. To the extent possible, we will also consider 
comments that Docket Management receives after that date. If Docket 
Management receives a comment too late for us to consider in developing 
the final rule, we will consider that comment as an informal suggestion 
for future rulemaking action.

How can I read the comments submitted by other people?

    You may read the comments received by Docket Management at the 
address given above under ADDRESSES. The hours of the Docket are 
indicated above in the same location. You may also see the comments on 
the internet. To read the comments on the internet, go to

[[Page 26737]]

http://www.regulations.gov. Follow the online instructions for 
accessing the dockets.
    Please note that, even after the comment closing date, we will 
continue to file relevant information in the Docket as it becomes 
available. Further, some people may submit late comments. Accordingly, 
we recommend that you periodically check the Docket for new material.

X. Appendices to the Preamble

Appendix A. Table Comparing GTR No. 20, FMVSS No. 305, and FMVSS No. 
305a

    Table A below provides an overview of the requirements presently 
in the GTR No. 20, FMVSS No. 305, and the proposed FMVSS No. 305a 
for light vehicles (LVs) and heavy vehicles (HVs).

     Table A--Overview of Safety Requirements in GTR No. 20, FMVSS No. 305, and Those Proposed in This NPRM
----------------------------------------------------------------------------------------------------------------
      Requirement category             Requirement           GTR No. 20       FMVSS No. 305      FMVSS No. 305a
----------------------------------------------------------------------------------------------------------------
Electrical Safety under Normal   Physical Barrier        Yes for LV and HV  Yes for LV.......  Yes for LV and
 Vehicle Operations.              Protection Electrical                                         HV.
                                  Isolation Isolation
                                  Monitoring (FCEVs)
                                  Charging Safety
                                  Driver Error
                                  Mitigation.
Post-Crash Safety..............  REESS Retention         Yes for LV.......  Yes for LV.......  Yes for LV and
                                  Electrolyte Leakage                                           heavy school
                                  Electrical Safety.                                            bus.
                                 Fire Safety...........  .................  No...............
Post-Crash Electrical Safety     Low Voltage Electrical  Yes for LV.......  Yes for LV.......  Yes for LV and
 Compliance Options.              Isolation Physical                                            heavy school
                                  Barrier Protection.                                           bus.
                                 Low Energy              Yes for LV.......  No...............  Yes for LV and
                                  (Capacitors).                                                 heavy school
                                                                                                bus.
Optional Post-crash Component    Mechanical Crush Test   Yes for LV.......  No...............  No.
 Level REESS Tests.               instead of crash test.
                                 Mechanical Shock Test   Only shock test
                                  instead of crash test.  for HV.
REESS Safety Performance during  Overcharge Over-        Yes for LV and HV  No...............  Yes for LV and
 Normal Vehicle Operations.       Discharge Over-                                               HV.
                                  Current Over-
                                  Temperature External
                                  Short-Circuit Low-
                                  Temperature Thermal
                                  Propagation Water
                                  Exposure REESS
                                  Venting.
                                 Vibration Thermal       Yes for HV and LV  No...............  No.
                                  Shock & Cycling Fire
                                  Resistance.
Warning Requirements...........  Thermal Event Warning.  Yes for LV and HV  No...............  Yes for LV and
                                                                                                HV.
                                 Warning of Malfunction
                                  of Vehicle Controls
                                  for REESS Operations.
                                 Low SOC...............  .................  .................  No.
Emergency Response Information.  Rescue Sheets.........  No...............  No...............
                                 Emergency Response      .................  .................  Yes for LV and
                                  Guides (ERGs).                                                HV.
----------------------------------------------------------------------------------------------------------------

Appendix B. Request for Comment on Phase 2 GTR No. 20 Approaches Under 
Consideration by the IWG

1. Electrolyte Release and Venting From the REESS

    NHTSA requests comment on the IWG's continuing work on venting. 
Phase 2 of GTR No. 20 is considering more robust methods to verify 
the occurrence and quantification of electrolyte release \145\ and/
or venting.\146\ Two possible approaches for detection of 
electrolyte release are under consideration: (1) detection of solid 
and liquid Li-ion, and (2) gas detection for the vapors released 
from the liquid electrolyte and vented gases.
---------------------------------------------------------------------------

    \145\ EVS21-E2TG-0200 [EC]. Detection of electrolyte leakage by 
gas detection techniques. https://wiki.unece.org/display/trans/EVS+21st+session.
    \146\ Gas emissions in thermal runaway propagation experiments, 
https://wiki.unece.org/download/attachments/177242909/EVS25-E2TG-0400%20%5BEC%5DGas%20emissions%20in%20thermal%20runaway%20propagation%20experiments.pdf?api=v2.
---------------------------------------------------------------------------

    Chemosensors \147\ are currently being studied to detect the 
presence of Li-ion resulting from electrolyte release. However, no 
commercially available chemosensors have been identified that could 
be used for testing purposes to reliably detect electrolyte leakage.
---------------------------------------------------------------------------

    \147\ Chemosensors indicate the presence of Li-ion through a 
color and fluorescence change. Chemosensor means a molecule which is 
able to simultaneously bind and signal the presence of other 
species. F. Pina et al, J. Photochem. Photobiol. A, 126 (1999), 65-
69.
---------------------------------------------------------------------------

    Common gas detection methods include gas chromatography, 
fourier-transform infrared spectroscopy (FTIR), and different types 
of gas sensors. Emitted gases under consideration include carbon 
dioxide (CO2), carbon monoxide (CO), hydrogen 
(H2), oxygen (O2), light C1-
C5 hydrocarbons, e.g., methane and ethane, and fluorine-
containing compounds such as hydrogen fluoride (HF) and fluoro-
organics such as e.g., ethyl-fluoride. However, practical, and cost-
effective methods of sampling the leakage/emissions/venting and 
determining acceptable exposure levels for different gases are still 
under development.
    NHTSA seeks comment on:
     How these detection methods (chemosensors and gas 
detection methods) may best be utilized in a vehicle level test 
procedure for both normal operating conditions and post-crash 
scenarios.
     How to best manage gases and particulates emitted from 
the REESS for both normal operating conditions and post-crash 
scenarios.
     Which gases generated in and vented from Li-ion 
batteries should be focused on for all types of REESS chemistries 
and are anticipated to remain relevant as REESS

[[Page 26738]]

chemistry and technology changes in the future.
     Practicable methods to verify the occurrence of 
electrolyte release and venting and to quantify the vented gases and 
vapors.

2. Single-Cell Thermal Runaway

    The IWG is considering a test-based approach during Phase 2 of 
GTR No. 20. GTR No. 20 would require that the thermal propagation 
test procedure fulfill the following conditions:
     Triggering of thermal runaway at a single-cell level 
must be repeatable, reproducible, and practicable,
     Judgment of thermal runaway through common sensors, 
e.g., voltage and temperature, needs to be practical, repeatable, 
and reproducible, and
     Judgement of whether consequent thermal events involve 
severe thermal propagation hazards, needs to be unequivocal and 
evidence based.
    The two main initiation methods under consideration in Phase 2 
are a localized rapid external heating method and a nail penetration 
method. The localized rapid external heating method is comprised of 
a film heater which is attached to an initiation cell's surface. The 
heater is turned on and set to reach its maximum power, and only 
turned off after thermal runaway occurs. In the nail penetration 
method, a steel nail 3 mm in diameter or more, with a circular cone 
is inserted into the initiation cell at a speed of 0.1 ~ 10 mm/s, 
which internally short-circuits the cell, inducing thermal runaway.
    Current GTR No. 20 specifies three conditions in which thermal 
runaway can be detected:
    1. The measured voltage of the initiation cell drops,
    2. The measured temperature exceeds the maximum operating 
temperature defined by the manufacturer, and
    3. The instantaneous rate of temperature change (dT/dt) >=1 
[deg]C/s of the measured temperature.
    Per GTR No. 20, thermal runaway can be judged when both (1) and 
(3) are detected, or both (2) and (3) are detected.
    For the test procedure development, the only operational mode 
originally considered was the active driving possible mode. As 
discussions continue in Phase 2, other operational modes such as 
parking and externally charging are also under consideration. 
However, the test methods and performance criteria are still under 
development.
    NHTSA conducted thermal runaway propagation tests on four 
different electric vehicle models using both the localized rapid 
external heating method \148\ and the nail penetration (NP) 
method.\149\ The criteria for identifying whether thermal runaway 
was initiated as described in ISO-6469-1:2019/DAM 1:2021(E) were 
used. Six tests were conducted at the vehicle level (with REESS 
installed in the vehicle) on four vehicle makes and models as shown 
in Table B-1.
---------------------------------------------------------------------------

    \148\ Thermal Runaway Initiation Method (TRIM) heater developed 
by the National Research Council (NRC) Canada.
    \149\ The testers used a generic nail similar to that specified 
in the ISO-6469-1:2019/DAM 1 1:2021(E).

   Table B-1--Thermal Runaway Propagation Tests Using Two Different Methods of Initiating Thermal Runaway on a
                                                   Single Cell
----------------------------------------------------------------------------------------------------------------
                                                                   Thermal runaway initiation method
                                                     -----------------------------------------------------------
         Vehicle make, model, and model year            Localized external rapid
                                                              heater method            Nail penetration method
----------------------------------------------------------------------------------------------------------------
2019 Chevrolet Bolt.................................                             X
2020 Nissan Leaf....................................                             X
2020 Tesla Model 3..................................              X, X (Two tests)
2021 Chevrolet Bolt.................................                             X                             X
2021 Nissan Leaf....................................                                                           X
2022 Kia Niro.......................................                             X                             X
----------------------------------------------------------------------------------------------------------------
Note--X represents a test was conducted.

    Thermal runaway was initiated using the localized heating method 
in tests with both the 2019 and 2021 Chevrolet Bolt vehicles, the 
2020 Nissan Leaf, 2020 Tesla Model 3, and the 2022 Kia Niro. Two 
tests using the localized heating method were conducted on the 2020 
Tesla Model 3 because the first test did not result in a thermal 
runaway. Tests were conducted on the 2021 Chevrolet Bolt, 2021 
Nissan Leaf, and the 2022 Kia Nero using the nail penetration method 
for initiating thermal runaway.
    Significant information was needed from the manufacturers on 
opening up the battery pack and on selecting the cell for initiating 
thermal runaway using both methods. The selection of the cell for 
initiating thermal runaway was not random and was based on which 
cells were accessible; the cells were not necessarily those that are 
more likely to cause thermal propagation if a thermal runaway was 
initiated. Copious amounts of smoke were released within and outside 
of the passenger cabin before flames were observed. Some of the gas 
emissions include hydrogen (flammable) and carbon monoxide (toxic). 
All vehicles tested have REESSs with pouch cells except for the 
Tesla Model 3, whose REESS has cylindrical cells. In the first Tesla 
Model 3, the initial heater was unsuccessful in transferring heat 
into the target cell due to lack of back pressure on the heater. In 
the second test, the target cell went into thermal runaway but 
experienced a side wall rupture towards the outside of the battery 
pack.\150\ The timing of the smoke emissions and the thermal 
propagation was not the same for the two methods of initiating 
thermal runaway in a single cell of the REESS. The results of the 
tests and the timing of various events are shown in Table B-2 below.
---------------------------------------------------------------------------

    \150\ Side wall rupture does not represent thermal runaway 
events observed in the field.

                                  Table B-2--Single-Cell Thermal Runaway and Propagation Test Results--Timing of Events
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                   External smoke  Smoke in cabin  External flame   Warning observed  Venting observed      CO in ppm
            Method                   Vehicle          (min:sec)       (min:sec)       (min:sec)        (min:sec)          (min:sec)         (min:sec)
--------------------------------------------------------------------------------------------------------------------------------------------------------
TRIM..........................  2019 Chevrolet              00:15           00:38           22:29  No...............  Yes.............  N/A.
                                 Bolt.
TRIM..........................  2021 Chevrolet              00:17           01:10           08:17  Yes (00:51)......  Yes.............  >100 ppm
                                 Bolt.                                                                                                   (02:20),
                                                                                                                                        >1500 ppm
                                                                                                                                         (03:30).
NP............................  2021 Chevrolet              00:07           03:10           11:58  Yes (00:27)......  Yes.............  >100 ppm
                                 Bolt.                                                                                                   (07:30),
                                                                                                                                        >1200 ppm
                                                                                                                                         (08:58).
TRIM..........................  2020 Nissan Leaf.           00:25           04:45           31:09  Yes (00:45)......  Yes.............  N/A.
NP............................  2021 Nissan Leaf.           00:05           01:10           24:48  Yes (00:34)......  Yes.............  >100 ppm
                                                                                                                                         (10:10),
                                                                                                                                        >800 ppm
                                                                                                                                         (21:30).
TRIM..........................  2020 Tesla Model              N/A             N/A             N/A  No...............  No..............  N/A.
                                 3.
TRIM..........................  2021 Tesla Model            00:28             N/A             N/A  No...............  Yes.............  N/A.
                                 3.

[[Page 26739]]

 
TRIM..........................  2022 Kia Niro....           01:01           03:57          177:03  No...............  Yes.............  25 ppm (05:25).
NP............................  2022 Kia Niro....           07:16           14:40           59:31  No...............  Yes.............  >100 ppm
                                                                                                                                         (14:20).
--------------------------------------------------------------------------------------------------------------------------------------------------------

    For the localized rapid external heating method, the heating 
element parameter may vary depending on the different battery 
chemistries or cell type (e.g., large prismatic cells versus 
cylindrical cells).\151\ More stable chemistries will require higher 
heat inputs than less stable chemistries. Calorimetric testing may 
need to be implemented to provide insights on what heating input 
parameters would be representative to avoid penalizing more stable 
cell chemistries, since they may require higher heat inputs to 
induce thermal runaway. The nail penetration method may be 
implemented in lieu of the localized rapid external heating method 
for more stable chemistries. It remains unclear whether the two 
initiation methods under consideration are equivalent in stringency. 
NHTSA's research results indicate that the timing of thermal 
propagation is different for the different thermal runaway 
initiation methods for the same vehicle models. The rapid heating 
and nail penetration thermal runaway initiation methods can be 
applied to only some cells in the REESS or REESS subsystem; only the 
cells that can be accessed and modified without impinging on 
adjacent cells in the pack can be triggered in these tests.\152\ 
Additionally, the criteria for assessing whether thermal runaway has 
occurred in a cell needs further development.
---------------------------------------------------------------------------

    \151\ ISO 6469-1:2019/DAM1:2021(E), ``Electrically propelled 
road vehicles--Safety specifications--Part 1: Rechargeable energy 
storage system (RESS)--Draft Amendment 1.''
    \152\ NHTSA's testing experience indicates that these testable 
cells are generally located along the edges of a module. The result 
of single-cell thermal runaway will vary with location based on heat 
transfer to adjacent cells and other components.
---------------------------------------------------------------------------

    Part of the performance criteria for a thermal runaway 
propagation test under consideration is for some form of warning to 
vehicle occupants and/or bystanders outside the vehicle in the event 
of thermal propagation within and outside the REESS. However, NHTSA 
considers warning to be a secondary mitigation strategy which would 
not prevent the thermal propagation from occurring in the first 
place. Thermal propagation resulting in EV fires are difficult to 
extinguish and may cause significant damage to adjacent structures 
and may pose a safety risk to people nearby, even when a warning is 
provided. In comparison, in the agency's view, the proposed 
documentation requirements provide a holistic risk mitigation of 
thermal propagation events resulting from single-cell thermal 
runaway due to an internal short-circuit within the cell. This risk 
mitigation would include of a cell in an REESS significantly before 
thermal runaway occurs to allow for appropriate action to be taken. 
Vehicle manufacturers are currently incorporating such technologies 
into the BMS to predict and evaluate the status of individual cells 
and mitigate the occurrence of single cell thermal runaway (SCTR) in 
the first place.
    NHTSA seeks comment on the proposed reporting requirements to 
mitigate the risk of SCTR due to an internal short-circuit in a 
single cell of the REESS and the performance test under 
consideration in GTR No. 20 Phase 2.

3. REESS Vibration Requirements

    Currently, during Phase 2 development of GTR No. 20, there are 
discussions for updating the vibration test to include vibration in 
all three orthogonal axes and at higher amplitudes and frequency 
range. NHTSA seeks comment on the safety need that would warrant an 
update to a more stringent vibration test than that already in UN 
38.3 Test T3.\153\ NHTSA seeks comment from vehicle manufacturers on 
practices they have implemented to avoid reliability issues and 
assure customer satisfaction in the field.
---------------------------------------------------------------------------

    \153\ The vibration load spectrum in GTR No. 20 was derived from 
UN 38.3.4.3 ``Recommendation on the Transport of Dangerous Goods, 
Manual of Tests and Criteria.'' https://unece.org/fileadmin/DAM/trans/danger/publi/manual/Rev7/Manual_Rev7_E.pdf.
---------------------------------------------------------------------------

List of Subjects in 49 CFR Part 571

    Imports, Incorporation by Reference, Motor vehicles, Motor vehicle 
safety.

Proposed Regulatory Text

    In consideration of the foregoing, NHTSA proposes to amend 49 CFR 
part 571 as set forth below.

PART 571--FEDERAL MOTOR VEHICLE SAFETY STANDARDS

0
1. The authority citation for part 571 continues to read as follows:

    Authority:  49 U.S.C. 322, 30111, 30115, 30117, and 30166; 
delegation of authority at 49 CFR 1.95.

0
2. Section 571.5 is amended by adding paragraphs (i)(5), (i)(6), and 
(i)(7), to read as follows:


Sec.  571.5  Matter incorporated by reference.

* * * * *
    (i) * * *

* * *
    (5) ISO 17840-1:2022 (E), ``Road vehicles--Information for first 
and second responders--Part 1: Rescue sheet for passenger cars and 
light commercial vehicles,'' Second Edition, February 2022, into Sec.  
571.305a.
    (6) ISO 17840-2:2019 (E), ``Road vehicles--Information for first 
and second responders--Part 2: Rescue sheet for buses, coaches and 
heavy commercial vehicles,'' First edition, April 2019, into Sec.  
571.305a.
    (7) ISO 17840-3:2019 (E), '' Road vehicles--Information for first 
and second responders--Part 3: Emergency response guide template,'' 
First Edition, April 2019, into Sec.  571.305a.
* * * * *
0
3. Section 571.305a is added to read as follows:


Sec.  571.305a  Standard No. 305a; Electric-Powered Vehicles: Electric 
Powertrain Integrity; Mandatory applicability begins on (this date will 
be the compliance date of the final rule).

    S1. Scope. This standard specifies requirements for protection from 
harmful electric shock, fire, explosion, and gas venting during normal 
vehicle operation and during and after a crash.
    S2. Purpose. The purpose of this standard is to reduce deaths and 
injuries during normal vehicle operations and during and after a crash 
that occur because of electrolyte leakage, intrusion of electric energy 
storage/conversion devices into the occupant compartment, electric 
shock, fire, explosion, and gas venting, including deaths and injuries 
due to driver error.
    S3. Application. This standard applies to passenger cars, 
multipurpose passenger vehicles, trucks, and buses that use electrical 
propulsion components with working voltages greater than 60 volts 
direct current (VDC) or 30 volts alternating current (VAC), and whose 
speed attainable over a distance of 1.6 km on a paved level surface is 
more than 40 km/h.
    S4. Definitions.
    Active driving possible mode means the vehicle mode when 
application of pressure to the accelerator pedal (or activation of an 
equivalent control) or release of the brake system causes the electric 
power train to move the vehicle.
    Automatic disconnect means a device that when triggered, 
conductively separates a high voltage source from the electric power 
train or the rest of the electric power train.
    Breakout harness means connector wires that are connected for 
testing purposes to the REESS on the traction side of the automatic 
disconnect.

[[Page 26740]]

    Capacitor means a device used to store electrical energy, 
consisting of one or more pairs of conductors separated by an 
insulator: x-capacitors are connected between electrical mains or 
neutral and y-capacitors are connected between a main to ground.
    Charge connector is a conductive device that, by insertion into a 
vehicle charge inlet, establishes an electrical connection of the 
vehicle to an external electric power supply for the purpose of 
transferring energy.
    Chassis dynamometer means a mechanical device that uses one or more 
fixed roller assemblies to simulate different road conditions within a 
controlled environment and is used for a wide variety of vehicle 
testing.
    Connector means a device providing mechanical connection and 
disconnection of high voltage electrical conductors to a suitable 
mating component, including its housing.
    n C Rate means the constant current of the REESS, which takes 1/n 
hours to charge or discharge the REESS between 0 and 100 percent state 
of charge.
    Direct contact is the contact of any person or persons with high 
voltage live parts.
    Electric energy storage device means a high voltage source that 
stores energy for vehicle propulsion. This includes, but is not limited 
to, a high voltage battery or battery pack, rechargeable energy storage 
device, and capacitor module.
    Electric energy storage/conversion device means a high voltage 
source that stores or converts energy for vehicle propulsion. This 
includes, but is not limited to, a high voltage battery or battery 
pack, fuel cell stack, rechargeable energy storage device, and 
capacitor module.
    Electric energy storage/conversion system means an assembly of 
electrical components that stores or converts electrical energy for 
vehicle propulsion. This includes, but is not limited to, high voltage 
batteries or battery packs, fuel cell stacks, rechargeable energy 
storage systems, capacitor modules, inverters, interconnects, and 
venting systems.
    Electric power train means an assembly of electrically connected 
components which includes, but is not limited to, electric energy 
storage/conversion systems and propulsion systems.
    Electrical chassis means conductive parts of the vehicle whose 
electrical potential is taken as reference and which are:
    (1) conductively linked together, and
    (2) not high voltage sources during normal vehicle operation.
    Electrical isolation of a high voltage source in the vehicle means 
the electrical resistance between the high voltage source and any of 
the vehicle's electrical chassis divided by the working voltage of the 
high voltage source.
    Electrical protection barrier is the part providing protection 
against direct contact with high voltage live parts from any direction 
of access.
    Electrolyte leakage means the escape of liquid electrolyte from the 
REESS.
    Emergency response guide means a document containing in-depth 
vehicle-specific information related to fire, submersion, leakage of 
fluids, towing, and storage of vehicles for first and second 
responders.
    Exposed conductive part is the conductive part that can be touched 
under the provisions of the IPXXB protection degree and that is not 
normally energized, but that can become electrically energized under 
isolation fault conditions. This includes parts under a cover if the 
cover can be removed without using tools.
    External Charging mode means the vehicle mode when the REESS is 
charging with external electric power supply connected through the 
charge connector to the vehicle charge inlet.
    External electric power supply is a power supply external to the 
vehicle that provides electric power to charge the electric energy 
storage device in the vehicle through the charge connector.
    First responder means a person with specialized training such as a 
law enforcement officer, paramedic, emergency medical technician, and/
or firefighter.
    Fuel cell system is a system containing the fuel cell stack(s), air 
processing system, fuel flow control system, exhaust system, thermal 
management system, and water management system.
    High voltage live part means a live part of a high voltage source.
    High voltage source means any electric component which is contained 
in the electric power train or conductively connected to the electric 
power train and has a working voltage greater than 30 VAC or 60 VDC.
    Indirect contact is the contact of any person or persons with 
exposed conductive parts.
    Live part is a conductive part of the vehicle that is electrically 
energized under normal vehicle operation.
    Luggage compartment is the space in the vehicle for luggage 
accommodation, separated from the passenger compartment by the front or 
rear bulkhead and bounded by a roof, hood or trunk lid, floor, and side 
walls, as well as by electrical protection barriers provided for 
protecting the occupants from direct contact with high voltage live 
parts.
    Normal vehicle operation includes operating modes and conditions 
that can reasonably be encountered during typical operation of the 
vehicle, such as driving, parking, and standing in traffic, as well as 
charging using chargers that are compatible with the specific charging 
ports installed on the vehicle. It does not include conditions where 
the vehicle is damaged, either by a crash or road debris, subjected to 
fire or water submersion, or in a state where service and/or 
maintenance is needed or being performed.
    Parking mode is the vehicle mode in which the vehicle power is 
turned off, the vehicle propulsion system and ancillary equipment such 
as the radio are not operational, and the vehicle is stationary.
    Passenger compartment is the space for occupant accommodation that 
is bounded by the roof, floor, side walls, doors, outside glazing, 
front bulkhead and rear bulkhead or rear gate, as well as electrical 
protection barriers provided for protecting the occupants from direct 
contact with high voltage live parts.
    Propulsion system means an assembly of electric or electro-
mechanical components or circuits that propel the vehicle using the 
energy that is supplied by a high voltage source. This includes, but is 
not limited to, electric motors, inverters/converters, and electronic 
controllers.
    Protection degree IPXXB is protection from contact with high 
voltage live parts. It is tested by probing electrical protection 
barriers with the jointed test finger probe, IPXXB, in Figure 7b.
    Protection degree IPXXD is protection from contact with high 
voltage live parts. It is tested by probing electrical protection 
barriers with the test wire probe, IPXXD, in Figure 7a.
    Rechargeable Electrical Energy Storage System (REESS) means the 
rechargeable electric energy storage system that provides electric 
energy for electrical propulsion.
    Rescue sheet means an abbreviated version of an emergency response 
guide that gives quick information about a vehicle's construction, 
intended for use by first and second responders at the scene of a 
crash.
    Rupture means an opening through the casing of the REESS that would 
permit the IPXXB test probe to penetrate and contact live parts.
    Second responder means a worker who supports first responders by 
cleaning up a site, towing vehicles, and/

[[Page 26741]]

or supporting services after an event requiring first responders.
    Service disconnect is the device for deactivation of an electrical 
circuit when conducting checks and services of the vehicle electrical 
propulsion system.
    State of charge (SOC) means the available electrical charge in a 
tested device expressed as a percentage of its rated capacity.
    Thermal event means the condition when the temperature within the 
REESS is significantly higher than the maximum operating temperature.
    Thermal runaway means an uncontrolled increase of cell temperature 
caused by exothermic reactions inside the cell.
    Thermal propagation means the sequential occurrence of thermal 
runaway within a REESS triggered by thermal runaway of a cell in the 
REESS.
    VAC means volts of alternating current (AC) expressed using the 
root mean square value.
    VDC means volts of direct current (DC).
    Vehicle charge inlet is the device on the electric vehicle into 
which the charge connector is inserted for the purpose of transferring 
energy and exchanging information from an external electric power 
supply.
    Venting means the release of excessive internal pressure from cell 
or battery in a manner intended by design to preclude rupture or 
explosion.
    Working voltage means the highest root mean square voltage of the 
voltage source, which may occur across its terminals or between its 
terminals and any conductive parts in open circuit conditions or under 
normal operating conditions.
    S5. General Requirements.
    S5.1 Vehicles of GVWR of 4,536 kilograms (kg) or less (light 
vehicles). Each vehicle with a GVWR of 4,536 kg or less shall meet the 
requirements set forth in S6 (normal vehicle operation safety), S8 
(post-crash safety), S11 (vehicle controls managing REESS safe 
operations), S13.2 (thermal event in REESS warning), S14 (water 
exposure safety), and S15 (emergency response information).
    S5.2 Vehicles with a GVWR greater than 4,536 kg other than school 
buses (heavy vehicles other than school buses). Each heavy vehicle with 
a GVWR greater than 4,536 kg, other than school buses, shall meet the 
requirements set forth in S6 (normal vehicle operation safety), S11 
(vehicle controls managing REESS safe operations), S13.2 (thermal event 
in REESS warning), S14 (water exposure safety), and S15 (emergency 
response information).
    S5.3 School buses with a GVWR greater than 4,536 kg. Each school 
bus with a GVWR greater than 4,536 kg shall meet the requirements set 
forth in S6 (normal vehicle operation safety), S8 (post-crash safety), 
S11 (vehicle controls managing REESS safe operations), S13.2 (thermal 
event in REESS warning), S14 (water exposure safety), and S15 
(emergency response information).
    S6. Normal vehicle operation safety. Each vehicle to which this 
standard applies must meet the requirements in S6.1 to S6.6, when 
tested according to the relevant provisions in S7.
    S6.1 Protection against direct contact.
    S6.1.1 Marking. The symbol shown in Figure 6 shall be present on or 
near electric energy storage devices. The symbol in Figure 6 shall also 
be visible on electrical protection barriers which, when removed, 
expose live parts of high voltage sources. The symbol shall be yellow 
and the bordering and the arrow shall be black.
    S6.1.1.1 The marking is not required for electrical protection 
barriers that cannot be physically accessed, opened, or removed without 
the use of tools. Markings are not required for electrical connectors 
or the vehicle charge inlet.
    S6.1.2 High voltage cables. Cables for high voltage sources which 
are not located within electrical protection barriers shall be 
identified by having an outer covering with the color orange.
    S6.1.3 Service disconnect. For a service disconnect which can be 
opened, disassembled, or removed without tools, protection degree IPXXB 
shall be provided when tested under procedures specified in S7.3.1 
using the IPXXB test probe shown in Figures 7a and 7b.
    S6.1.4 Protection degree of high voltage live parts.
    (a) Protection degree IPXXD shall be provided for high voltage live 
parts inside the passenger or luggage compartment when tested according 
to the procedures specified in S7.3.1 using the IPXXD test probe shown 
in Figure 7a.
    (b) Protection degree IPXXB shall be provided for high voltage live 
parts in areas other than the passenger or luggage compartment when 
tested according to the procedures specified in S7.3.1 using the IPXXB 
test probe shown in Figures 7a and 7b.
    S6.1.5 Connectors. All connectors shall provide direct contact 
protection by:
    (a) Meeting the requirements specified in S6.1.4 when the connector 
is connected to its corresponding mating component; and,
    (b) If a connector can be separated from its mating component 
without the use of a tool, meeting at least one of the following 
conditions from (b)(1), (2), or (3) of this section:
    (1) The connector meets the requirements of S6.1.4 when separated 
from its mating component;
    (2) The voltage of the live parts becomes less than or equal to 60 
VDC or 30 VAC within one second after the connector is separated from 
its mating component; or,
    (3) The connector requires at least two distinct actions to 
separate from its mating component and there are other components that 
must be removed in order to separate the connector from its mating 
component and these other components cannot be removed without the use 
of tools.
    S6.1.6 Vehicle charge inlet. Direct contact protection for a 
vehicle charge inlet shall be provided by meeting the requirements 
specified in S6.1.4 when the charge connector is connected to the 
vehicle inlet and by meeting at least one of the requirements of 
subparagraphs (a) or (b).
    (a) The vehicle charge inlet meets the requirements of S6.1.4 when 
the charge connector is not connected to it; or
    (b) The voltage of the high voltage live parts becomes equal to or 
less than 60 VDC or equal to or less than 30 VAC within 1 second after 
the charge connector is separated from the vehicle charge inlet.
    S6.2 Protection against indirect contact.
    S6.2.1 The resistance between all exposed conductive parts of 
electrical protection barriers and the electrical chassis shall be less 
than 0.1 ohms when tested according to the procedures specified in 
S7.3.2
    S6.2.2 The resistance between any two simultaneously reachable 
exposed conductive parts of the electrical protection barriers that are 
less than 2.5 meters from each other shall be less than 0.2 ohms when 
tested according to the procedures specified in S7.3.2.
    S6.3 Electrical isolation.
    S6.3.1 Electrical isolation of AC and DC high voltage sources. The 
electrical isolation of a high voltage source, determined in accordance 
with the procedure specified in S7.2 must be greater than or equal to 
one of the following:
    (a) 500 ohms/volt for an AC high voltage source;
    (b) 100 ohms/volt for an AC high voltage source if it is 
conductively connected to a DC high voltage source, but only if the AC 
high voltage source meets the requirements for protection against 
direct contact in S6.1.4 and the

[[Page 26742]]

protection from indirect contact in S6.2; or
    (c) 100 ohms/volt for a DC high voltage source.
    S6.3.2 Exclusion of high voltage sources from electrical isolation 
requirements. A high voltage source that is conductively connected to 
an electric component which is conductively connected to the electrical 
chassis and has a working voltage less than or equal to 60 VDC, is not 
required to meet the electrical isolation requirements in S6.3.1 if the 
voltage between the high voltage source and the electrical chassis is 
less than or equal to 30 VAC or 60 VDC.
    S6.3.3 Electrical isolation of high voltage sources for charging 
the electric energy storage device. For the vehicle charge inlet 
intended to be conductively connected to the AC external electric power 
supply, the electric isolation between the electrical chassis and the 
high voltage sources that are conductively connected to the vehicle 
charge inlet during charging of the electric energy storage device 
shall be greater than or equal to 500 ohms/volt when the charge 
connector is disconnected. The electrical isolation is measured at the 
high voltage live parts of the vehicle charge inlet and determined in 
accordance with the procedure specified in S7.2. During the 
measurement, the electric energy storage device may be disconnected.
    S6.4 Electrical isolation monitoring. DC high voltage sources of 
vehicles with a fuel cell system shall be monitored by an electrical 
isolation monitoring system that displays a warning for loss of 
isolation when tested according to S7.4. The system must monitor its 
own readiness and the visual warning display must be provided to the 
driver. For a vehicle with autonomous driving systems and without 
manually-operated driving controls, the visual warning must be provided 
to all the front row occupants.
    S6.5 Electric shock protection during charging. For motor vehicles 
with an electric energy storage device that can be charged through a 
conductive connection with a grounded external electric power supply, a 
device to enable conductive connection of the electrical chassis to the 
earth ground shall be provided. This device shall enable connection to 
the earth ground before exterior voltage is applied to the vehicle and 
retain the connection until after the exterior voltage is removed from 
the vehicle.
    S6.6 Mitigating driver error.
    S6.6.1 Indicator of active driving possible mode. At least a 
momentary indication shall be given to the driver each time the vehicle 
is first placed in active driving possible mode after manual activation 
of the propulsion system. This requirement does not apply under 
conditions where an internal combustion engine directly or indirectly 
provides the vehicle's propulsion power when the vehicle is first 
placed in the active driving possible mode after manual activation of 
the propulsion system.
    S6.6.2 Indicator of active driving possible mode when leaving the 
vehicle. When leaving the vehicle, the driver shall be informed by an 
auditory or visual signal if the vehicle is still in the active driving 
possible mode.
    S6.6.3 Prevent drive-away. If the on-board electric energy storage 
device can be externally charged, vehicle movement of more than 150 mm 
by its own propulsion system shall not be possible as long as the 
charge connector of the external electric power supply is physically 
connected to the vehicle charge inlet in a manner that would permit 
charging of the electric energy storage device.
    S7. Electrical safety test procedures for normal vehicle operation 
safety. The following provisions specify the test procedures associated 
with the requirements of S6.
    S7.1 Voltage measurements. For the purpose of determining the 
voltage level of the high voltage source, voltage is measured as shown 
in Figure 1 using a voltmeter that has an internal resistance of at 
least 10 M[Omega]. All post-crash voltage measurements for determining 
electrical isolation of high voltage sources specified in S8.2(a), the 
voltage levels specified in S8.2(b), and the energy in capacitors 
specified in S8.2(d) are made between 10 to 60 seconds after impact.
    S7.1.1 For a high voltage source that has an automatic disconnect 
that is physically contained within itself, the voltage measurement 
after the test is made from the side of the automatic disconnect 
connected to the electric power train or to the rest of the electric 
power train if the high voltage source is a component contained in the 
power train. For a high voltage source that has an automatic disconnect 
that is not physically contained within itself, the voltage measurement 
after the test is made from both the high voltage source side of the 
automatic disconnect and from the side of the automatic disconnect 
connected to the electric power train or to the rest of the electric 
power train if the high voltage source is a component contained in the 
power train.
    S7.1.2 Voltage Vb is measured across the two terminals of the 
voltage source. Before a vehicle crash test, Vb is equal to or greater 
than the working voltage as specified by the vehicle manufacturer.
    S7.1.3 Voltage V1 is measured between the negative side of the high 
voltage source and the electrical chassis as shown in Figure 2. Voltage 
V2 is measured between the positive side of the high voltage source and 
the electrical chassis as shown in Figure 3.
    S7.2 Test method for determining electrical isolation. Measure the 
voltages V1, V2, and Vb as shown in Figure 1 in accordance with S7.1
    S7.2.1 If V1 is greater than or equal to V2, insert a known 
resistance (Ro) between the negative side of the high voltage source 
and the electrical chassis. With the Ro installed, measure the voltage 
(V1') as shown in Figure 4 between the negative side of the high 
voltage source and the electrical chassis. Calculate the electrical 
isolation resistance (Ri) according to the formula shown. Divide Ri (in 
ohms) by the working voltage of the high voltage source (in volts) to 
obtain the electrical isolation (in ohms/volt).
    S7.2.2 If V2 is greater than V1, insert a known resistance (Ro) 
between the positive side of the high voltage source and the electrical 
chassis. With the Ro installed, measure the voltage (V2') as shown in 
Figure 5 between the positive side of the high voltage source and the 
electrical chassis. Calculate the electrical isolation resistance (Ri) 
according to the formula shown. Divide Ri (in ohms) by the working 
voltage of the high voltage source (in volts) to obtain the electrical 
isolation (in ohms/volt).
    S7.3 Test methods for evaluating physical barrier protection.
    S7.3.1 Test method to evaluate protection from direct contact with 
high voltage sources.
    (a) Any parts surrounding the high voltage components are opened, 
disassembled, or removed without the use of tools.
    (b) The selected access probe is inserted into any gaps or openings 
of the electrical protection barrier with a test force between 9 Newton 
to 11 Newton with the IPXXB probe or 1 Newton to 2 Newton with the 
IPXXD probe. If the probe partly or fully penetrates into the 
electrical protection barrier, it is placed in every possible position 
to evaluate contact with high voltage live parts. If partial or full 
penetration into the electrical protection barrier occurs with the 
IPXXB probe, the IPXXB probe shall be placed as follows: starting from 
the straight position, both joints of the test finger are rotated 
progressively through an angle of up to 90 degrees with respect to the 
axis of the adjoining

[[Page 26743]]

section of the test finger and are placed in every possible position.
    (c) A low voltage supply (of not less than 40 V and not more than 
50 V) in series with a suitable lamp may be connected between the 
access probe and any high voltage live parts inside the electrical 
protection barrier to indicate whether high voltage live parts were 
contacted.
    (d) A mirror or fiberscope may be used to inspect whether the 
access probe touches high voltage live parts inside the electrical 
protection barrier.
    (e) Protection degree IPXXD or IPXXB is verified when the following 
conditions are met:
    (1) The access probe does not touch high voltage live parts. The 
IPXXB access probe may be manipulated as specified in S7.3.1(b) for 
evaluating contact with high voltage live parts. The methods specified 
in S7.3.1(c) or S7.3.1(d) may be used to aid the evaluation. If method 
S7.3.1(c) is used for verifying protection degree IPXXB or IPXXD, the 
lamp shall not light up.
    (2) The stop face of the access probe does not fully penetrate into 
the electrical protection barrier.
    S7.3.2 Test method to evaluate protection against indirect contact 
with high voltage sources. Any parts surrounding the high voltage 
components are opened, disassembled, or removed without the use of 
tools. At the option of the manufacturer, protection against indirect 
contact with high voltage sources shall be determined using the test 
method in subparagraph (a) or subparagraph (b).
    (a) Test method using a resistance tester. The resistance tester is 
connected to the measuring points (the electrical chassis and any 
exposed conductive part of electrical protection barriers or any two 
simultaneously reachable exposed conductive parts of electrical 
protection barriers that are less than 2.5 meters from each other), and 
the resistance is measured using a resistance tester that can supply 
current levels of at least 0.2 Amperes with a resolution of 0.01 ohms 
or less. The resistance between two exposed conductive parts of 
electrical protection barriers that are less than 2.5 meters from each 
other may be calculated using the separately measured resistances of 
the relevant parts of the electric path.
    (b) Test method using a DC power supply, voltmeter, and ammeter.
    (1) Connect the DC power supply, voltmeter, and ammeter to the 
measuring points (the electrical chassis and any exposed conductive 
part or any two simultaneously reachable exposed conductive parts that 
are less than 2.5 meters from each other) as shown in Figure 8.
    (2) Adjust the voltage of the DC power supply so that the current 
flow becomes more than 0.2 Amperes.
    (3) Measure the current I and the voltage V shown in Figure 8.
    (4) Calculate the resistance R according to the formula, R=V/I.
    (5) The resistance between two simultaneously reachable exposed 
conductive parts of electrical protection barriers that are less than 
2.5 meters from each other may be calculated using the separately 
measured resistances of the relevant parts of the electric path.
    S7.3.3 Test method to determine voltage between exposed conductive 
parts of electrical protection barriers and the electrical chassis and 
between exposed conductive parts of electrical protection barriers.
    (a) Any parts surrounding the high voltage components are opened, 
disassembled, or removed without the use of tools.
    (b) Connect the voltmeter to the measuring points (exposed 
conductive part of an electrical protection barrier and the electrical 
chassis or any two simultaneously reachable exposed conductive parts of 
electrical protection barriers that are less than 2.5 meters from each 
other).
    (c) Measure the voltage.
    (d) The voltage between two simultaneously reachable exposed 
conductive parts of electrical protection barriers that are less than 
2.5 meters from each other may be calculated using the separately 
measured voltages between the relevant electrical protection barriers 
and the electrical chassis.
    S7.4 Test method for evaluating on-board electrical isolation 
monitoring system.
    Prior to any impact test, the requirements of S6.4 for the on-board 
electrical isolation monitoring system shall be tested using the 
following procedure.
    (a) The electric energy storage device is at the state-of-charge 
specified in S7.1.
    (b) The switch or device that provides power from the electric 
energy storage/conversion system to the propulsion system is in the 
activated position or the ready-to-drive position.
    (c) Determine the isolation resistance, Ri, of the high voltage 
source with the electrical isolation monitoring system using the 
procedure outlined in S7.2.
    (d) Insert a resistor with resistance Ro equal to or greater than 
1/(1/(95 times the working voltage of the high voltage source)--1/Ri) 
and less than 1/(1/(100 times the working voltage of the high voltage 
source)--1/Ri) between the positive terminal of the high voltage source 
and the electrical chassis.
    (e) The electrical isolation monitoring system indicator shall 
provide a visual warning to the driver. For a vehicle with autonomous 
driving systems and without manually-operated driving controls, the 
visual warning must be provided to all the front row occupants.
    S7.5 Test method for determining post-crash energy in capacitors.
    (a) Prior to the crash tests, the vehicle manufacturer must 
identify the capacitors, type of capacitors (x-capacitors and y-
capacitors) and their respective capacitance (Cx and Cy) in the 
electric power train for which the low energy compliance option for 
post-crash electrical safety in S8.2(d) is applied.
    (b) Voltages Vb, V1, and V2 are measured across the capacitors in 
accordance with S7.1.
    (c) The energy in a x-capacitor is equal to 0.5 x Cx x Vb\2\
    (d) The energy in a y-capacitor is equal to 0.5 x Cy x (V1\2\ + 
V2\2\).
    S8. Post-crash safety. Each vehicle with a GVWR of 4,536 kg or less 
to which this standard applies, must meet the requirements in S8.1, 
S8.2, S8.3, and S8.4 when tested according to S9 under the conditions 
of S10. Each school bus with a GVWR greater than 4,536 kg to which this 
standard applies, must meet the requirements in S8.1, S8.2, S8.3, and 
S8.4 when tested according to S9.5 under the conditions of S10.
    S8.1 Fire safety. Starting from the time of impact and continuing 
until one hour after the completion of the sequence of tests specified 
in S9 of this standard, there shall be no evidence of fire or explosion 
in any part of the vehicle. The assessment of fire or explosion is 
verified by visual inspection without disassembly of the REESS or 
vehicle.
    S8.2 Electrical safety. After each test specified in S9 of this 
standard, each high voltage source in a vehicle must meet one of the 
following electrical safety requirements: electrical isolation 
requirements of subparagraph (a), the voltage level requirements of 
subparagraph (b), or the physical barrier protection requirements of 
subparagraph (c). High voltage capacitors in the electric power train 
may also meet electrical safety requirements using the low-energy 
requirements of subparagraph (d).
    (a) The electrical isolation of the high voltage source, determined 
in accordance with the procedure specified in S7.2, must be greater 
than or equal to one of the following:

[[Page 26744]]

    (1) 500 ohms/volt for an AC high voltage source; or
    (2) 100 ohms/volt for an AC high voltage source if it is 
conductively connected to a DC high voltage source, but only if the AC 
high voltage source meets the physical barrier protection requirements 
specified in S8.3(c)(1) and S8.3(c)(2); or
    (3) 100 ohms/volt for a DC high voltage source.
    (b) The voltages V1, V2, and Vb of the high voltage source, 
measured according to the procedure specified in S7.1, must be less 
than or equal to 30 VAC for AC components or 60 VDC for DC components.
    (c) Protection against electric shock by direct and indirect 
contact (physical barrier protection) shall be demonstrated by meeting 
the following three conditions:
    (1) The high voltage source (AC or DC) meets the protection degree 
IPXXB when tested according to the procedure specified in S7.3.1 using 
the IPXXB test probe shown in Figures 7a and 7b;
    (2) The resistance between exposed conductive parts of the 
electrical protection barrier of the high voltage source and the 
electrical chassis is less than 0.1 ohms when tested according to the 
procedures specified in S7.3.2. In addition, the resistance between an 
exposed conductive part of the electrical protection barrier of the 
high voltage source and any other simultaneously reachable exposed 
conductive parts of electrical protection barriers within 2.5 meters of 
it must be less than 0.2 ohms when tested using the test procedures 
specified in S7.3.2; and
    (3) The voltage between exposed conductive parts of the electrical 
protection barrier of the high voltage source and the electrical 
chassis is less than or equal to 30 VAC or 60 VDC as measured in 
accordance with S7.3.3. In addition, the voltage between an exposed 
conductive part of the electrical protection barrier of the high 
voltage source and any other simultaneously reachable exposed 
conductive parts of electrical protection barriers within 2.5 meters of 
it must be less than or equal to 30 VAC or 60 VDC as measured in 
accordance with S7.3.3.
    (d) The total energy of unidirectional single impulse currents from 
capacitors shall be less than 0.2 Joules when determined in accordance 
with the procedure specified in S7.5.
    S8.3 Electric energy storage/conversion device retention. During 
and after each test specified in S9 of this standard:
    (a) Electric energy storage/conversion devices shall remain 
attached to the vehicle by at least one component anchorage, bracket, 
or any structure that transfers loads from the device to the vehicle 
structure, and
    (b) Electric energy storage/conversion devices located outside the 
occupant compartment shall not enter the occupant compartment.
    S8.4 Electrolyte leakage from electric energy storage devices. Not 
more than 5.0 liters of electrolyte shall leak from electric energy 
storage devices, and no visible trace of electrolyte shall leak into 
the passenger compartment. Leakage is measured from the time of the 
impact until 30 minutes thereafter, and throughout any static rollover 
after a barrier impact test, specified in S9 of this standard.
    S9. Crash test specifications. A test vehicle with a GVWR less than 
or equal to 4,536 kg, under the conditions of S10, is subject to any 
one single barrier crash test of S9.1, S9.2, or S9.3, followed by the 
static rollover test of S9.4. A school bus with a GVWR greater than 
4,536 kg, under the conditions of S10, is subject to the contoured 
barrier crash test of S9.5. A particular vehicle need not meet further 
test requirements after having been subjected to a single barrier 
crash/static rollover test sequence.
    S9.1 Frontal barrier crash. The test vehicle, with test dummies in 
accordance with S6.1 of 571.301 of this chapter, traveling 
longitudinally forward at any speed up to and including 48 km/h, 
impacts a fixed collision barrier that is perpendicular to the line of 
travel of the vehicle, or at an angle up to 30 degrees in either 
direction from the perpendicular to the line of travel of the vehicle.
    S9.2 Rear moving barrier impact. The test vehicle, with test 
dummies in accordance with S6.1 of 571.301 of this chapter, is impacted 
from the rear by a barrier that conforms to S7.3(b) of 571.301 of this 
chapter and that is moving at any speed between 79 and 81 km/h.
    S9.3 Side moving deformable barrier impact. The test vehicle, with 
the appropriate 49 CFR part 572 test dummies specified in 571.214 at 
positions required for testing by S7.1.1, S7.2.1, or S7.2.2 of Standard 
214, is impacted laterally on either side by a moving deformable 
barrier moving at any speed between 52.0 km/h and 54.0 km/h.
    S9. 4 Post-impact test static rollover. After each crash test 
specified in S9.1, S9.2, and S9.3, without any alteration of the 
vehicle, the vehicle is rotated on its longitudinal axis to each 
successive increment of 90 degrees under the test conditions of S10.3.
    S9.5 Moving contoured barrier crash. The test vehicle, under the 
conditions of S10.1 and S10.2, is impacted at any point and at any 
angle by the moving contoured barrier assembly, specified in S7.5 and 
S7.6 in 571.301 of this chapter, traveling longitudinally forward at 
any speed up to and including 48 km/h.
    S10. Crash test conditions.
    S10.1 State-of-charge. The electric energy storage device(s) shall 
be at the state-of-charge specified in either subparagraph (a), (b), or 
(c):
    (a) At the maximum state-of-charge in accordance with the vehicle 
manufacturer's recommended charging procedures, as stated in the 
vehicle owner's manual or on a label that is permanently affixed to the 
vehicle; or
    (b) If the manufacturer has made no recommendation for charging 
procedures in the owner's manual or on a label permanently affixed to 
the vehicle, at a state-of-charge of not less than 95 percent of the 
maximum capacity of the electric energy storage device(s); or
    (c) If the electric energy storage device(s) is/are rechargeable 
only by an energy source on the vehicle, at any state-of-charge within 
the normal operating voltage defined by the vehicle manufacturer.
    S10.2 Vehicle conditions. The switch or device that provides power 
from the electric energy storage/conversion system to the propulsion 
system is in the activated position or the ready-to-drive position. 
Bypass any devices or systems that do not allow the propulsion system 
to be energized at the time of impact when the vehicle ignition is on 
and the vehicle is in neutral.
    S10.2.1 The parking brake is disengaged and the vehicle drive 
system is in the neutral position. In a test conducted under S9.3, the 
parking brake is set.
    S10.2.2 Tires are inflated to the manufacturer's specifications.
    S10.2.3 The vehicle, including test devices and instrumentation, is 
loaded as follows:
    (a) A passenger car is loaded to its unloaded vehicle weight plus 
its rated cargo and luggage capacity weight, secured in the luggage 
compartment, plus the necessary test dummies as specified in S9, 
restrained only by means that are installed in the vehicle for 
protection at its seating position.
    (b) A multipurpose passenger vehicle, truck, or bus, with a GVWR of 
4,536 kg (10,000 lb) or less, is loaded to its unloaded vehicle weight 
plus the necessary dummies, as specified in S9, plus 136 kg or its 
rated GVWR, whichever is less, secured in the load carrying area and 
distributed as nearly

[[Page 26745]]

as possible in proportion to its GVWR. For the purpose of this 
standard, unloaded vehicle weight does not include the weight of work-
performing accessories. Each dummy is restrained only by means that are 
installed in the vehicle for protection at its seating position.
    S10.3 Static rollover test conditions. The vehicle is rotated about 
its longitudinal axis, with the axis kept horizontal, to each 
successive increment of 90[deg], 180[deg], and 270[deg] at a uniform 
rate, with 90[deg] of rotation taking place in any time interval from 1 
to 3 minutes. After reaching each 90[deg] increment the vehicle is held 
in that position for 5 minutes.
    S10.4 Rear moving barrier impact test conditions. The conditions of 
S7.3(b) and S7.6 of 571.301 of this chapter apply to the conducting of 
the rear moving deformable barrier impact test specified in S9.2.
    S10.5 Side moving deformable barrier impact test conditions. The 
conditions of S8.9, S8.10, and S8.11 of 571.214 of this chapter apply 
to the conduct of the side moving deformable barrier impact test 
specified in S9.3.
    S11. Vehicle controls managing REESS safe operations. Each vehicle 
to which the standard applies shall meet the requirements in S11.1, 
S11.2, and S11.3, when tested according to S12.
    S11.1 When tested in accordance with the overcharge test in S12.1, 
the over-discharge test in S12.2, the overcurrent test in S12.3, the 
high-temperature test in S12.4, and the short-circuit test in 
accordance with S12.5, each vehicle shall meet the following:
    (a) During the test, there shall be no evidence of electrolyte 
leakage, rupture, venting, fire, or explosion of the REESS as verified 
by visual inspection without disassembly of the vehicle.
    (b) The isolation resistance of the high voltage sources measured 
after the test shall not be less than 100 ohms/volt when determined in 
accordance with S7.2.
    S11.2 The vehicle manufacturer must make available to the agency, 
upon request, documentation in accordance with S12.7 that demonstrates 
whether the vehicle is equipped with controls for REESS operations at 
or below the lower boundary REESS temperature threshold for safe REESS 
operations specified by the manufacturer.
    S11.3 The vehicle manufacturer must make available to the agency, 
upon request, documentation in accordance with S12.8 that demonstrates 
the activation of a visual warning, when the vehicle is in active 
driving possible mode to indicate operational failure of the vehicle 
controls that manage the safe operation of the REESS. The warning 
system shall monitor its own readiness and the visual warning must be 
provided to the driver. For a vehicle with autonomous driving systems 
and without manually operated driving controls, the visual warning must 
be provided to all the front row occupants.
    S12. Test methods and documentation for evaluating vehicle controls 
managing REESS safe operations.
    S12.1 Overcharge test. The overcharge test is conducted at ambient 
temperatures between 10 [deg]C and 30 [deg]C, with the vehicle REESS 
initially set between 90 to 95 percent SOC. The following steps are 
conducted to evaluate the vehicle's overcharge protection controls:
    (a) A breakout harness is connected to the traction side of the 
REESS. Manufacturer may specify an appropriate location(s) and 
attachment point(s) to connect the breakout harness.
    (b) Temperature probes are connected to the REESS outer casing to 
monitor changes in REESS temperature. Temperature measurements may also 
be obtained through communication with the REESS control module.
    (c) The external charge/discharge equipment, with maximum voltage 
and current set at least 10 percent higher than the REESS voltage and 
current limits, is connected to the breakout harness.
    (d) The vehicle switch or device that provides power to the vehicle 
controls that manage REESS operations is set to the activated position.
    (e) The REESS is charged with the external charge/discharge 
equipment with the maximum charge current specified by the 
manufacturer. If the manufacturer does not specify an appropriate 
charge current, then a charge rate of \1/3\C is used.
    (f) Charging is continued until the following occurs:
    (1) The overcharge protection control terminates the charge 
current;
    (2) The REESS temperature is 10 [deg]C above the manufacturer 
specified maximum operating temperature of the REESS; or
    (3) 12 hours have passed since the start of charging the vehicle.
    (g) After the charge current is terminated, if charge and discharge 
is permitted by the vehicle controls, a standard cycle is performed in 
accordance with S12.6.
    (h) After the completion of the standard cycle, or if the standard 
cycle was not performed, after charging is terminated, the vehicle is 
observed for 1 hour for evidence of electrolyte leakage, rupture, 
venting, fire, or explosion of the REESS.
    (i) At the conclusion of the test, electrical isolation of the 
REESS is determined in accordance with S7.2.
    S12.2 Over-discharge test. The over-discharge test is conducted at 
ambient temperatures between 10 [deg]C and 30 [deg]C, with the vehicle 
REESS initially set between 10 and 15 percent SOC. For a vehicle with 
on-board energy conversion systems such as an internal combustion 
engine or a fuel cell, the fuel supply is set to the minimum level 
where active driving possible mode is permitted. The following steps 
are conducted to evaluate the vehicle's over-discharge protection 
controls:
    (a) A breakout harness is connected to the traction side of the 
REESS. Manufacturer may specify an appropriate location(s) and 
attachment point(s) to connect the breakout harness.
    (b) Temperature probes are connected to the REESS outer casing to 
monitor changes in REESS temperature. Temperature measurements may also 
be obtained through communication with the REESS control module.
    (c) The external charge/discharge equipment, with maximum voltage 
and current set at least 10 percent higher than the REESS voltage and 
current limits, is connected to the breakout harness.
    (d) The vehicle switch or device that provides power from the REESS 
to the electric power train is set to the activated position or the 
active driving possible mode.
    (e) The REESS is discharged with the external charge/discharge 
equipment with the maximum discharge rate under normal operating 
conditions specified by the manufacturer. If the manufacturer does not 
specify an appropriate discharge rate, a power load of 1kW is used.
    (f) Discharging is continued until the following occurs:
    (1) The over-discharge protection control terminates the discharge 
current;
    (2) The temperature gradient of the REESS is less than 4 [deg]C 
through 2 hours from the start of discharge; or
    (3) the vehicle is discharged to 25 percent of its nominal voltage 
level.
    (g) After the discharge current is terminated, a standard cycle is 
performed in accordance with S12.6, if charge and discharge is 
permitted by the vehicle controls.
    (h) After the completion of the standard cycle, or if the standard 
cycle was not performed, after discharging is terminated, the vehicle 
is observed for 1 hour for evidence of electrolyte leakage, rupture, 
venting, fire, or explosion of the REESS.

[[Page 26746]]

    (i) At the conclusion of the test, electrical isolation of the 
REESS is determined in accordance with S7.2.
    S12.3 Overcurrent test. The overcurrent test is only conducted on 
vehicles that have the capability of charging by DC external 
electricity supply. The test is conducted at ambient temperatures 
between 10 [deg]C and 30 [deg]C, with the vehicle REESS initially set 
between 40 to 50 percent SOC. The following steps are conducted to 
evaluate the vehicle's over-current protection controls:
    (a) A breakout harness is connected to the traction side of the 
REESS. Manufacturer may specify an appropriate location(s) and 
attachment point(s) to connect the breakout harness.
    (b) Temperature probes are connected to the REESS outer casing to 
monitor changes in REESS temperature. Temperature measurements may also 
be obtained through communication with the REESS control module.
    (c) The external charge/discharge equipment, with maximum voltage 
and current set at least 10 percent higher than the REESS voltage and 
current limits, is connected to the breakout harness.
    (d) The vehicle switch or device that provides power to the vehicle 
controls that manage REESS operations is set to the activated position.
    (e) The REESS is charged with the external charge/discharge 
equipment with the maximum charge current specified by the 
manufacturer. If the manufacturer does not specify an appropriate 
charge current, then a charge rate of \1/3\C is used.
    (f) After charging is initiated, the overcurrent specified by the 
manufacturer is supplied over the course of 5 seconds from the maximum 
charge current level to the over-current level. If the vehicle 
manufacturer does not supply an overcurrent level, a 10 Ampere over-
current is supplied over 5 seconds. If charging is not terminated, the 
over-current supply is increased in steps of 10 Amperes.
    (g) Charging at the over-current level is continued until the 
following occurs:
    (1) The over-current protection control terminates the charge 
current; or
    (2) The temperature gradient of the REESS is less than 4 [deg]C 
through 2 hours from the first overcurrent input;
    (h) After the charge current is terminated, if charge and discharge 
is permitted by the vehicle controls, a standard cycle is performed in 
accordance with S12.6.
    (i) After the completion of the standard cycle or if the standard 
cycle was not performed, after charging is terminated, the vehicle is 
observed for 1 hour for evidence of electrolyte leakage, rupture, 
venting, fire, or explosion of the REESS.
    (j) At the conclusion of the test, electrical isolation of the 
REESS is determined in accordance with S7.2.
    S12.4 Over-temperature test. The overtemperature test is conducted 
at ambient temperatures between 10 [deg]C and 30 [deg]C on a chassis-
dynamometer with the vehicle REESS initially set between 90 to 95 
percent SOC. For a vehicle with on-board energy conversion systems such 
as an internal combustion engine or a fuel cell, the fuel supply is set 
to allow operation for about one hour of driving. The following steps 
are conducted to evaluate the vehicle's high temperature protection 
controls:
    (a) The cooling system of the REESS is disabled using manufacturer 
supplied information. For an REESS that will not operate if the cooling 
system is disabled, the cooling operation is significantly reduced. If 
manufacturer does not supply information to disable or significantly 
reduce the cooling system, methods such as crimping the liquid cooling 
hose, removing refrigerant fluid, or blocking cabin air intakes for air 
cooled REESS are applied.
    (b) Temperature probes are connected to the REESS outer casing to 
monitor changes in REESS temperature. Temperature measurements may also 
be obtained through communication with the REESS control module.
    (c) The vehicle is installed on a chassis dynamometer and the 
vehicle switch or device that provides power from the REESS to the 
electric power train is set to the activated position or the active 
driving possible mode.
    (d) The vehicle is driven on the dynamometer using an appropriate 
vehicle manufacturer supplied drive profile and charging information 
for discharge and charge of the REESS to raise the REESS temperature to 
its upper boundary safe operating temperature within one hour. If an 
appropriate manufacturer supplied drive profile is not available, the 
vehicle is repeatedly accelerated to 80 mph and then decelerated to 15 
mph within 40 seconds. If the manufacturer does not supply a charge 
profile, then a charge rate greater than \1/3\C current is used.
    (e) The discharge/charge procedure on the chassis-dynamometer is 
continued until the following occurs:
    (1) The vehicle terminates the discharge/charge cycle;
    (2) The temperature gradient of the REESS is less than 4 [deg]C 
through 2 hours from the start of the discharge/charge cycle; or
    (3) 3 hours have passed since the start of discharge/charge cycles.
    (g) After the discharge and charge procedure is terminated, if 
charge and discharge is permitted by the vehicle controls, a standard 
cycle is performed in accordance with S12.6.
    (h) After the completion of the standard cycle, or if the standard 
cycle is not performed, after the discharge and charge procedure is 
terminated, the vehicle is observed for 1 hour for evidence of 
electrolyte leakage, rupture, venting, fire, or explosion of the REESS.
    (i) At the conclusion of the test, electrical isolation of the 
REESS is determined in accordance with S7.2.
    S12.5 External Short circuit test. The short circuit test is 
conducted at ambient conditions with the vehicle REESS initially set 
between 90 to 95 percent SOC. The following steps are conducted to 
evaluate the vehicle's overcharge protection controls:
    (a) A breakout harness is connected to the REESS. Manufacturer may 
specify an appropriate location(s) and attachment point(s) to connect 
the breakout harness.
    (b) Temperature probes are connected to the REESS outer casing to 
monitor changes in REESS temperature. Temperature measurements may also 
be obtained through communication with the REESS control module.
    (c) The vehicle switch or device that provides power to the vehicle 
controls that manage REESS operations is set to the activated position.
    (d) The short circuit contactor (with the contactors in open 
position) is connected to the breakout harnesses. The total resistance 
of the equipment to create the external short circuit (short circuit 
contactor and breakout harnesses) is verified to be between 2 to 5 
milliohms.
    (e) The short circuit contactor is closed to initiate the short-
circuit.
    (f) The short circuit condition is continued until the following 
occurs:
    (1) Short circuit current is terminated; or
    (2) The temperature gradient of the REESS is less than 4 [deg]C 
through 2 hours from the start of initiating the short circuit 
condition.
    (g) After the short circuit current is terminated, if charge and 
discharge is permitted by the vehicle controls, a standard cycle is 
performed in accordance with S12.6.
    (h) After the completion of the standard cycle, or if the standard 
cycle was not performed, after short circuit current is terminated, the 
vehicle is observed for 1 hour for evidence of electrolyte leakage, 
rupture, venting, fire, or explosion of the REESS.

[[Page 26747]]

    (i) At the conclusion of the test, electrical isolation of the 
REESS is determined in accordance with S7.2.
    S12.6 Standard cycle. The standard cycle is conducted at ambient 
temperatures between 10 [deg]C and 30 [deg]C and starts with a standard 
discharge followed by a standard charge. The discharge and charge 
procedures would follow manufacturer supplied information. The charge 
procedure is initiated 15 minutes after discharge is terminated.
    (a) If the manufacturer does not provide a discharge procedure, the 
vehicle is discharged with 1C current until discharge is terminated by 
vehicle controls.
    (b) If the manufacturer does not provide a charge procedure, the 
vehicle is charged with \1/3\C current until terminated by vehicle 
controls.
    S12.7 Documentation for low temperature operation safety. At 
NHTSA's request, each manufacturer shall submit documentation that 
includes the following:
    (a) The make, model, model year, and production dates of the 
vehicles to which the submitted documentation applies.
    (b) The lower temperature boundary for safe REESS operation in all 
vehicle operating modes.
    (c) A description and explanation of charge and discharge rates at 
the lower temperature boundary for safe REESS operation.
    (d) A description of the method used to detect REESS temperature.
    (e) A system diagram with key components and subsystems involved in 
maintaining safe REESS charging and discharging operation for 
temperatures at or below the lower temperature boundary for safe REESS 
operation.
    (f) A description of how the vehicle controls, ancillary equipment, 
and design features were validated and verified for maintaining safe 
REESS operations at or below the lower temperature boundary for safe 
REESS operation.
    (g) Overall evaluation: A description of the final manufacturer 
review/audit process and results of any final review or audit 
evaluating the technical content and the completeness and verity of 
S12.7(a) to S12.7(f).
    S12.8 Documentation and visual warning in the event of operational 
failure of vehicle controls.
    (a) During the vehicle's active driving mode, the vehicle shall 
provide a visual warning to the driver when there is a vehicle control 
malfunction.
    (b) At NHTSA's request, each manufacturer shall submit 
documentation that includes the following:
    (1) The make, model, model year, and production dates of the 
vehicles to which the submitted documentation applies.
    (2) A system diagram that identifies all the vehicle controls that 
manage REESS operation. The diagram must identify what components are 
used to generate a visual warning indicating malfunction of vehicle 
controls to conduct one or more basic operations.
    (3) A written explanation describing the basic operation of the 
vehicle controls that manage REESS operation. The explanation must 
identify the components of the vehicle control system, provide 
description of their functions and capability to manage the REESS, and 
provide a logic diagram and description of conditions that would lead 
to triggering the telltale activation.
    (4) Validation results from tests to confirm the display of a 
visual warning in the presence of a malfunction of the vehicle controls 
which manage safe operation of the REESS.
    (5) Overall evaluation: A description of the final manufacturer 
review/audit process and results of the final review or audit which 
evaluated the technical content and the completeness and verity of 
S12.8(b)(1) to S12.8(b)(4).
    S13. REESS thermal propagation safety.
    S13.1 Thermal runaway due to internal short in a single cell of the 
REESS. The vehicle manufacturer shall make available to the agency, 
upon request, documentation demonstrating how the vehicle and its REESS 
are designed to mitigate the safety risks associated with thermal 
propagation resulting from a single cell thermal runaway due to an 
internal short within the cell. The documentation shall demonstrate 
thermal propagation safety risk mitigation for the vehicle in external 
charging mode, active driving possible mode, and parking mode. The 
documentation shall include the following:
    (a) The make, model, model year, and production dates of the 
vehicles to which the submitted documentation applies.
    (b) Part I: System analysis. This part of the documentation shall 
identify the conditions which could lead to single-cell thermal runaway 
due to an internal short-circuit in different vehicle operational modes 
and allocate applicable functional units, components, subsystems to 
each identified condition. This part shall include:
    (1) A system diagram and a description of all relevant physical 
systems and components of the REESS, including information about the 
cell type and electrical configuration, cell chemistry, electrical 
capacity, voltage, current limits during charging and discharging, 
thermal limits of the components that are critical for thermal 
propagation safety.
    (2) A system diagram, operational description of sensors, 
components, functional units relevant to single-cell thermal runaway 
due to internal short-circuit and thermal propagation, and the 
interrelationship between the identified sensors, components, and 
functional units;
    (3) A description of conditions under which a single-cell thermal 
runaway and propagation event due to an internal short-circuit could 
occur;
    (4) A description of how the identified conditions were allocated 
to each identified component, functional unit, and subsystem;
    (5) A description of the process used to review the identified 
conditions and their allocation to the identified sensors, components, 
and functional units, for completeness and validity; and
    (6) A description of the warning or notification system before the 
thermal runaway occurred, including a description of the detection 
technology and mitigation strategies, if any.
    (c) Part II: Safety risk assessment and mitigation process. This 
part of the documentation shall identify thermal propagation safety 
risk mitigation strategies for identified conditions leading to single 
cell thermal runaway in Part I and include:
    (1) A description of the safety risks and safety risk mitigation 
strategies, and how these were identified, and
    (2) A description of how each risk mitigation strategy manages, 
mitigates, or prevents the identified safety risks.
    (3) Safety risk mitigation strategies identified should include 
those that mitigate the risk of single cell thermal runaway due to an 
internal short and mitigate the occurrence of thermal propagation due 
to single-cell thermal runaway resulting from an internal short-circuit 
within the cell.
    (d) Part III: Verification and validation of risk mitigation 
strategies. This part of the documentation pertains to verification 
that the manufacturer identified safety risks and considered safety 
risk mitigation strategies and include:
    (1) A description of how each risk mitigation strategy was verified 
and validated for effectiveness,
    (2) A description of the verification and validation results for 
each risk mitigation strategy, and

[[Page 26748]]

    (3) A description of and results from the vehicle level assessment.
    (e) Part IV: Overall evaluation of risk mitigation. This part of 
the documentation summarizes the vehicle design and manufacturing 
strategies and their validation to mitigate the safety risks associated 
with thermal propagation due single cell thermal runaway resulting from 
internal short within a cell. This part shall include a description of 
the final manufacturer review/audit process and results of the final 
review or audit evaluating the technical content and the completeness 
and verity of S13.1(a) to S13.1(d).
    S13.2 Warning in the case of thermal event in REESS. The vehicle 
shall provide a warning to the driver of a thermal event in the REESS. 
The warning shall activate within three minutes of activating a heater 
within the REESS when tested in accordance with S13.3. The warning 
shall consist of auditory and visual signals that remain active for at 
least 5 minutes. The thermal event warning system must monitor its own 
readiness and the warning must be provided to the driver.
    S13.3 Test procedure for evaluating warning for thermal event in 
REESS. The thermal event warning test is conducted at ambient 
temperatures between 10 [deg]C and 30 [deg]C with the vehicle REESS 
initially set between 90 to 95 percent SOC. The following steps are 
conducted to evaluate the warning in the case of thermal event in the 
REESS:
    (a) If possible, the REESS is removed from the vehicle.
    (b) The REESS casing is opened.
    (c) A heater that achieves a peak temperature of 600 [deg]C within 
30 seconds is attached to one or more cells in the REESS in a manner to 
put at least one cell in the REESS into thermal runaway.
    (d) The REESS casing is closed and the REESS is reinstalled into 
the vehicle (if initially removed in (a)).
    (e) Vehicle stops to prevent vehicle rollaway are installed.
    (f) The vehicle is placed in active driving possible mode.
    (g) The heater within the REESS is activated to achieve 600 [deg]C 
within 30 seconds. The heater shall remain operational until thermal 
runaway is initiated in at least one cell.
    (h) The time for the activation of the warning to the front row 
occupant (if any) from the time of activation of the heater is noted.
    (i) The test is terminated after activation of the warning or after 
four minutes of activating the heater in the REESS, whichever comes 
first.
    S14. Water exposure safety. Each vehicle to which the standard 
applies shall maintain electrical isolation as specified in S6.3.1 and 
S6.3.2 at these times: (a) just after exposure to water in each of the 
two tests specified below and with the vehicle still wet; and (b) after 
a minimum of 24 hours after completing each of the tests specified 
below.
    S14.1 Vehicle washing test. The vehicle is sprayed from any 
direction with a stream of freshwater from a standard test nozzle shown 
in Figure 9 that has a nozzle internal diameter of 6.3 millimeters, 
delivery rate of 11.9 to 13.2 liters/minute, and water pressure at the 
nozzle between 30 kPa to 35 kPa.
    (a) During the washing, the distance from the nozzle to the vehicle 
surface is 3.0 to 3.2 meters. The distance of the nozzle from the 
vehicle surface may be reduced, if necessary, to ensure the surface is 
wet when spraying upwards. The washing test duration per square meter 
of the vehicle surface area is 60 to 75 seconds, with a minimum total 
test duration of 3 minutes.
    (b) The vehicle external surface, including the vehicle sides, 
front, rear, top, and bottom is exposed to the water stream. Border 
lines on the vehicle such glass seals, outline of opening parts (doors, 
windows, vehicle inlet cover), outline of front grille, seals of 
vehicle lamps are exposed to the water stream from any direction.
    (c) At the conclusion of the normal washing test, with the vehicle 
still wet, electrical isolation is determined in accordance with S7.2.
    S14.2 Driving through standing water test. The vehicle is driven 
through a wade pool of at least 10 centimeters but not more than 15 
centimeters depth of freshwater for a distance of 500 meters at a 
minimum speed of 12 mph (20 km/h) but not more than 15 mph (24 km/h).
    (a) If the wade pool is less than 500 m in length, then the vehicle 
shall be driven through it several times for a total distance of 500 m. 
The total time, including the period outside of the wade pool, shall be 
less than 5 minutes.
    (b) At the conclusion of the standing water test, with the vehicle 
still wet, electrical isolation is determined in accordance with S7.2.
    S15. Rescue Sheets and Emergency Response Guides.
    S15.1 Rescue Sheets. Prior to vehicle certification per 49 CFR part 
567, vehicle manufacturers shall submit rescue sheets to NHTSA.
    (a) For vehicles with a GVWR less than or equal to 4,536 kg to 
which the standard applies, submitted rescue sheets shall follow the 
layout and format in ISO-17840-1:2022(E).
    (b) For vehicles with a GVWR greater than 4,536 kg to which the 
standard applies, the submitted rescue sheets shall follow the layout 
and format in ISO-17840-2:2019(E).
    (c) The rescue sheets shall provide information for first 
responders to extricate occupants.
    S15.2 Emergency Response Guides. Prior to vehicle certification per 
49 CFR part 567, vehicle manufacturers shall submit to NHTSA Emergency 
Response Guides (ERGs) in accordance with the template layout and 
format in ISO-17840-3:2019(E) for vehicles to which this standard 
applies.
    (a) The ERGs shall provide in-depth information linked and aligned 
to the corresponding rescue sheet to support the quick and safe action 
of first responders and second responders.
    (b) The ERGs shall provide in-depth information related to electric 
vehicle fire, submersion, leakage of fluids, towing, transportation, 
and storage.
    (c) The ERGs shall provide information to assist first responders 
in extricating occupants.

Figures to FMVSS No. 305a

BILLING CODE 4910-59-P

[[Page 26749]]

[GRAPHIC] [TIFF OMITTED] TP15AP24.048

Figure 1. Voltage Measurements of the High Voltage Source
[GRAPHIC] [TIFF OMITTED] TP15AP24.049

Figure 2. Measurement for V1 Voltage Between the Negative Side of the 
High Voltage Source and the Electrical Chassis

[[Page 26750]]

[GRAPHIC] [TIFF OMITTED] TP15AP24.050

Figure 3. Measurement for V2 Voltage Between the Positive Side of the 
High Voltage Source and the Electrical Chassis
[GRAPHIC] [TIFF OMITTED] TP15AP24.051

Figure 4. Measurement for V1' Voltage Across Resistor Between Negative 
Side of the High Voltage Source and Electrical Chassis

[[Page 26751]]

[GRAPHIC] [TIFF OMITTED] TP15AP24.052

Figure 5. Measurement for V2' Voltage Across Resistor Between Positive 
Side of the High Voltage Source and Electrical Chassis
[GRAPHIC] [TIFF OMITTED] TP15AP24.053

Figure 6. Marking of High Voltage Sources

[[Page 26752]]

[GRAPHIC] [TIFF OMITTED] TP15AP24.054

Figure 7a. Access Probes for the Tests of Direct Contact Protection. 
Access Probe IPXXB (Top) and Access Probe IPXXD (Bottom)

[[Page 26753]]

[GRAPHIC] [TIFF OMITTED] TP15AP24.055

Figure 7b. Jointed Test Finger IPXXB

[[Page 26754]]

[GRAPHIC] [TIFF OMITTED] TP15AP24.056

Figure 8. Connection To Determine Resistance Between Exposed Conductive 
Parts of Electrical Protection Barrier and Electrical Chassis
[GRAPHIC] [TIFF OMITTED] TP15AP24.057

Figure 9. Standard Nozzle for IPX5 Water Exposure Test

    Issued in Washington, DC, under authority delegated in 49 CFR 
1.95 and 501.5.
Sophie Shulman,
Deputy Administrator.
[FR Doc. 2024-07646 Filed 4-12-24; 8:45 am]
BILLING CODE 4910-59-C