NHTSA proposes updating electrical safety requirements for fuel cell and mild hybrid vehicles; alignment with int’l standards
The US Department of Transportation's National Highway Traffic Safety Administration (NHTSA) issued a notice of proposed rulemaking (NPRM) to update electrical safety requirements for hydrogen fuel cell vehicles and mild hybrid vehicles.
The NPRM proposes adding an optional method for post-crash electrical safety into the standard, FMVSS No. 305, that involves physical barriers to prevent electric shock due to direct or indirect contact of high voltage sources. This proposed optional method affords the same level of electric shock protection as the other methods for electrical safety currently in FMVSS No. 305 and would enable innovative powertrain technologies. The proposed updates to FMVSS No. 305 align the standard with international regulations and the latest version of the voluntary industry standard, SAE J1766, “Recommended Practice for Electric and Hybrid Electric Vehicle Battery Systems Crash Integrity Testing”.
FMVSS No. 305 currently only has post-crash electrical safety requirements. The NPRM seeks to expand the standard’s performance requirements beyond post-crash conditions by adopting the electrical safety requirements during normal vehicle operation that are specified in United Nations Global Technical Regulations (GTR) Nº 13. The NPRM also proposes an optional method of meeting electrical isolation requirements in certain conditions that would allow fuel cell vehicles to be offered for sale in the US.
GTR Nº 13, “Hydrogen fuel cell vehicles,” addresses hydrogen fuel cell vehicle technology. NHTSA closely collaborated with experts from contracting parties to the 1998 Agreement, particularly Germany and Japan, to develop a GTR for hydrogen-fueled vehicles that would establish levels of safety that are equivalent to or exceeds those for conventional gasoline-fueled vehicles. The collaborative effort in this process led to the establishment of GTR Nº 13 in June 2013.
The US voted on 27 June 2013 in favor of establishing GTR Nº 13. In voting yes to establishing the GTR, NHTSA is obligated to “submit the technical Regulation to the process” used in the US to adopt the requirement into our law or regulation. By issuance of the NPRM, NHTSA is initiating the process for considering adoption of GTR Nº 13.
One purpose of FMVSS No. 305 is to reduce deaths and injuries from electrical shock. The standard requires vehicles with high voltage sources to meet certain performance criteria to protect vehicle occupants, rescue workers and others who may come in contact with the vehicle after a crash. Among other things, FMVSS No. 305 requires that after a crash, high voltage sources in a vehicle are either (a) electrically isolated from the vehicle’s chassis or (b) their voltage is below specified levels considered safe from electric shock hazards. Since the physiological impacts of direct current (DC) are less than those of alternating current (AC), the standard specifies lower minimum electrical isolation requirements for certain DC components (100 ohms/volt) than for AC components (500 ohms/volt).
GTR Nº 13 also has requirements intended to reduce deaths and injuries from electrical shock. Unlike FMVSS No. 305, GTR Nº 13 has requirements that reduce the risk of harmful electric shock during normal vehicle operation. This NPRM proposes to adopt those requirements to expand FMVSS No. 305’s performance requirements beyond post-crash conditions. In addition, while the various post-crash compliance options in GTR No. 13 are similar to those in FMVSS No. 305, GTR No. 13 includes a compliance option for electrical vehicle safety that prevents direct and indirect contact of high voltage sources by way of “physical barriers.” NHTSA is now proposing to amend FMVSS No. 305 to permit a physical barrier compliance option.
NHTSA said that the effect of the proposal would be to enable wider use of hydrogen fuel cell and mild hybrid vehicles. Toyota Motor North America and the Alliance of Automobile Manufacturers had submitted separate petitions for rulemaking seeking to update the standard to enable innovative powertrain systems.
Today’s proposal would provide more options in building safety into electric and fuel-cell cars and help automakers develop and sell more fuel-efficient vehicles. US consumers would be able to purchase a wider variety of vehicles with high fuel efficiency and zero or low emissions without any decrease in safety. At the same time, the proposed rule would better align NHTSA regulations with global industry standards.—NHTSA Administrator Mark Rosekind