Pictured here is an illustration of a high-voltage, lithium-ion battery in an electric vehicle,...

Pictured here is an illustration of a high-voltage, lithium-ion battery in an electric vehicle, showing the location of the vehicle’s battery pack, a detail of the battery module, and a size comparison between the lithium-ion batteries in the module and a typical AA battery.

National Transportation Safety Board graphic by Christy Spangler

The National Transportation Safety Board (NTSB) issued on Wednesday four safety recommendations based on its investigation of four electric vehicle (EV) fires involving high-voltage, lithium-ion batteries and hazards posed to emergency responders.

Fires in EVs powered by high-voltage lithium-ion batteries pose the risk of electric shock to emergency responders from exposure to the high-voltage components of a damaged lithium-ion battery, according to a news release from the NTSB. Another risk is that damaged cells in the battery can experience thermal runaway — uncontrolled increases in temperature and pressure — which can lead to battery reignition. The risks of electric shock and battery reignition/fire arise from the “stranded” energy that remains in a damaged battery.

The federal agency’s findings are based on three lithium-ion batteries that ignited and were damaged in high-speed, high-severity crashes, and a fourth lithium-ion battery fire occurred during normal vehicle operations.

All three of the crash-damaged batteries reignited after firefighters extinguished the vehicle fires. The battery in the fourth investigation did not reignite.

Safety issues with the high-voltage, lithium-ion batteries used in EVs first gained widespread attention when a Chevrolet Volt caught fire three weeks after a crash test in May 2011, according to the NTSB.

The federal agency’s first investigation of EV battery fires on U.S. roadways was in 2017, when a high-voltage lithium-ion battery caught fire after an EV left the road and crashed into a residential garage at high speed.

Between 2017 and 2018, the NTSB investigated two other EV high-speed, high-severity crashes that resulted in post-crash fires and one non-crash fire. During its investigations, the NTSB considered the safety risks to first and second responders posed by the vehicles’ high-voltage, lithium-ion batteries. Those risks are addressed in the NTSB’s Safety Report 20/01, “Safety Risks to Emergency Responders from Lithium-Ion Battery Fires in Electric Vehicles.”

The report identified two main safety issues in its investigation:

  • The inadequacy of vehicle manufacturers’ emergency response guides.
  • The gaps in safety standards and research related to high-voltage lithium-ion batteries involved in high-speed, high-severity crashes.

Here’s a summary of the NTSB’s recommendations:

  • To the National Highway Traffic Safety Administration (NHTSA): When determining a vehicle’s U.S. New Car Assessment Program score, factor in the availability of a manufacturer’s emergency response guide and its adherence to International Organization for Standardization standard 17840 and SAE International recommended practice J2990. (H-20-30)

    Additionally, NHTSA should convene a coalition of stakeholders to continue research on mitigating or de-energizing stranded energy in high-voltage lithium-ion batteries, reducing the hazards associated with thermal runaway resulting from high-severity crashes, and publish the research results. (H-20-31).
  • To manufacturers of EVs equipped with high-voltage lithium-ion batteries: Model emergency response guides on International Organization for Standardization standard 17840, as included in SAE International recommended practice J2990, and incorporate vehicle-specific information on fighting high-voltage lithium-ion battery fires; mitigating thermal runaway and the risks of high-voltage lithium-ion battery reignition and stranded energy; and safely storing an EV with a damaged high-voltage lithium-ion battery. (H-20-32)
  • To fire protection associations: Inform members about the circumstances of the fire risks described in the report and the guidance available to emergency personnel who respond to high-voltage lithium-ion battery fires in EVs. (H-20-33)

To highlight the lessons learned in the report, the NTSB produced a video that is available on the NTSB’s YouTube Channel.

Originally posted on School Bus Fleet