NHTSA proposal aims to promote fuel cells, mild hybrids

New rules are claimed to make it easier for automakers to integrate hydrogen powertrains in a wider range of vehicles.

Federal safety regulators have outlined a proposal that aims to bolster development of hydrogen fuel-cell and mild hybrid vehicles.

The National Highway Traffic Safety Administration wants to update its rules regarding electrical safety requirements for such technology, aligning US laws with internationally-accepted regulations and voluntary industry standards.

Notably, the proposal includes a provision to protect high-voltage sources via "physical barriers," to prevent electrical shock and injuries to occupants or first responders in an accident. EVs are currently designed with an electrical disconnect system that breaks the conductive link to the battery in an accident.

Toyota and the Alliance of Automobile Manufacturers submitted a petition arguing that the regulations should not require a mechanical disconnect system to activate in low-speed accidents, as vehicles can be effectively disabled due to minor 'fender benders.' The Alliance further claimed that the NHTSA's high-voltage definition, which starts at 30 volts, serves as a development barrier to modern 48-volt electrical systems that are needed to run electric compressors and other innovative technologies.

"Since these systems are grounded to the vehicle chassis, they cannot meet FMVSS No. 305's existing electrical isolation option," the automakers said. "While it is feasible to design a 48 volt mild hybrid system that is isolated from the chassis and meets FMVSS No. 305's electrical isolation requirements, such designs involve more complexity, higher consumer costs, and higher mass resulting in reduced fuel economy and increased emissions."

The NHTSA believes its relaxed rules will allow mild hybrid technology and hydrogen fuel cells to be used in a wider range of vehicles, simplifying development work and aligning US laws with global standards.

"A key component of the Department's safety mission is ensuring that our regulations are up-to-date and provide the highest level of safety possible," said US Transportation Secretary Anthony Foxx. "Today's proposal not only boosts our efforts to increase fuel efficiency and energy security; it also builds on our efforts to encourage technology innovation."