September 22, 2021
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The National Transportation Safety Board issued several safety recommendations on January 13 to improve first responder safety when facing electric vehicle fires involving high-voltage lithium-ion batteries.

[Above graphic by the NTSB.}

Those findings are contained in Safety Report 20/01, which documents the agency’s investigation of four such EV fires.

In three of those cases, the lithium-ion batteries ignited after being damaged in high-speed, high-severity crashes, NTSB said, with the fourth lithium-ion battery fire occurred during normal vehicle operations.

[Editor’s note: the NTSB issued a video, seen below, summarizing its EV battery fire-fighting recommendations.]

All three of the crash-damaged batteries reignited after firefighters initially extinguished the vehicle fires, the agency noted, while the battery pack in the fourth investigation did not reignite.

“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,” NTSB said in a statement.

“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 re-ignition,” the agency added. “The risks of electric shock and battery re-ignition/fire arise from the ‘stranded’ energy that remains in a damaged battery.”

The agency’s safety recommendations include:

  • Mitigating thermal runaway and the risk of high-voltage lithium-ion battery re-ignition.
  • Mitigating risks associated with stranded energy in high-voltage lithium-ion batteries during emergency response and before removing a damaged electric vehicle 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.
editor@aashto.org

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