Firefighters doused the blazing Tesla Inc. Model X's battery pack, and then company engineers removed about one-quarter of its power cells before the vehicle was deemed safe to tow off a California freeway.
That didn't prevent the powerful and highly flammable lithium ion battery cells from reigniting. The car caught fire twice more within 24 hours of the March 23 fatal crash, and again six days later, according to a safety bulletin from the fire department in Mountain View.
Fires on electric vehicles are rare, but the volatile chemistry of their batteries and the need for special training on how to extinguish them raises new safety questions as automakers are poised to dramatically increase production. Techniques for putting out burning gasoline-fueled vehicles could worsen a blaze in a battery powered one.
"We're in uncharted waters here," said Donald Sadoway, a professor of materials chemistry at the Massachusetts Institute of Technology. "When you start putting 70 kilowatt-hour packs in a car, it's very different than what happens in a cellphone."
The growing popularity of lithium-based batteries that power everything from personal electronics to bicycles has periodically been marred by outbreaks of fires. Blazes in e-cigarettes, laptops and even battery packs on one of the most sophisticated jetliners in the world, the Boeing Co. 787, have led to government restrictions and frightening headlines.
The U.S. National Transportation Safety Board has opened investigations into two recent Tesla fires, along with an earlier blaze last year. The agency charged with setting vehicle safety standards, the National Highway Traffic Safety Administration, on Thursday announced it was also gathering information on the most recent episode, on May 8 in Fort Lauderdale, Fla. Swiss police are also examining a fatal Tesla crash last week that triggered a fire.
The issue isn't new. NHTSA also has conducted reviews of battery fires in the past, including a Chevrolet Volt that caught fire in 2011, several weeks after the agency conducted crash tests on the vehicle. Other manufacturers whose cars have been involved in fires include the former Fisker Inc. and Mitsubishi Motors Corp.