The National Transportation Safety Board issued four safety recommendations based on findings contained in Safety Report 20/01 which documents the agency’s investigation of four electric vehicle fires involving high-voltage, lithium-ion battery fires.
Three of the lithium-ion batteries that ignited were damaged in high-speed, high-severity crashes, and the 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 Report 20/01 identified two main safety issues through 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.
Actions sought by the NTSB in the four safety recommendations issued Wednesday include:
- Factoring 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, when determining a U.S. New Car Assessment Program score.
- Continued research on ways to mitigate or deenergize stranded energy in high-voltage lithium-ion batteries.
- Continued research on ways to reduce the hazards associated with thermal runaway resulting from high-speed, high-severity crashes.
- Manufacturer emergency response guides modeled on ISO standard 17840 and SAE International recommended practice J2990.
- Incorporation of vehicle-specific information in emergency response guides for:
Fighting high-voltage lithium-ion battery fires.
- Mitigating thermal runaway and the risk of high-voltage lithium-ion battery reignition.
- Mitigating risks associated with stranded energy in high-voltage lithium-ion batteries during emergency response and before a damaged electric vehicle is removed from the scene.
- Safely storing an electric vehicle with a damaged high-voltage lithium-ion battery.
- Providing information and available guidance to first responders and other crash scene workers about fire risks associated with high-voltage lithium-ion battery fires in electric vehicles.
Fires in electric vehicles 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. A further 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 National Transportation Safety Board has an interest in the safety of emerging technology, including alternative vehicle fuel sources such as lithium-ion batteries. Safety issues with the high-voltage, lithium-ion batteries used in electric vehicles first gained widespread attention when a Chevrolet Volt caught fire three weeks after a crash test in May 2011.
The NTSB’s first investigation of electric vehicle battery fires on US roadways was in 2017, when a high-voltage lithium-ion battery caught fire after an electric vehicle left the road and crashed into a residential garage at high speed.
Between 2017 and 2018 the NTSB investigated two other electric vehicle high-speed, high-severity crashes that resulted in post-crash fires and one non-crash fire. During the course of 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.”
To highlight the lessons learned in Safety Report 20/01 the NTSB produced a short video that is available on the NTSB’s YouTube Channel at https://www.youtube.com/watch?v=J6eS6JzBn0k.