Electric car battery fires rare but challenging to extinguish, rescue officials say

Electric car battery fires occur roughly six to seven times a year in Finland, making them rare compared with the approximately 1,200 passenger car fires recorded annually, according to rescue service statistics.

“Combustion-engine cars burn almost daily, but electric cars less than once a month,” said Kimmo Rytkönen, a teacher at the Emergency Services Academy Finland. He said he expects the number of battery fires to rise as the vehicle fleet ages.

When an electric car’s battery pack enters thermal runaway—a chemical reaction inside the cells—extinguishing the fire becomes a matter of managing that reaction rather than simply putting out flames, said Ismo Huttu, principal lecturer at the academy. The only way to control thermal runaway is to cool the battery pack, using either external cooling, water injection through a hole drilled into the pack, or submerging the vehicle.

Cooling takes at least half an hour in a real incident and requires thousands of litres of water, Huttu said. “If the extinguishing equipment under the car delivers 150 litres per minute and it takes 30 minutes, you can do the math. And 30 minutes may not be enough.”

If a driver hears an unusual sound or sees pale smoke from the battery during a journey, they should pull over immediately and exit the vehicle. “There is nothing you can do except call the emergency number,” Rytkönen said, noting that the smoke from the battery is toxic.

The difficulty increases when the burning electric car is indoors, as the toxic smoke can form an acid when combined with moisture and may even penetrate a firefighter’s protective suit, Rytkönen explained.

Battery packs can also reignite later. “There have been cases worldwide where the battery has reignited even two weeks later,” Rytkönen said. As a precaution, a burned electric car must be placed in quarantine for a minimum of two days, he added.

The Emergency Services Academy in Kuopio now includes training on cooling electric car battery packs, using a gas fire to simulate a battery blaze. Students practise with a six-metre extinguishing lance placed under the vehicle while a second water stream is aimed at the car from above.