A crashed and burnt-out Tesla Model S.
A crashed and burnt-out Tesla Model S from an NTSB report.

A new National Transportation Safety Board report on the fatal Florida crash of a Tesla Model S highlights the unique fire safety challenges posed by the batteries that power electric cars.

In the May 8 Fort Lauderdale crash, first responders used 200 to 300 gallons of water and foam to extinguish the flames, according to the NTSB preliminary report (PDF). After the fire was out and the vehicle was loaded onto a tow truck, the car caught fire again. After that fire was extinguished and the car was in the storage yard, it ignited a third time. A different fire department responded and put that blaze out.

According to Andrew Klock, emerging technologies program manager at the National Fire Protection Association in Quincy, Mass., electric vehicles (EVs) aren’t inherently more prone to fires than conventional gasoline cars. But when their batteries do ignite, the fires can behave very differently from gasoline blazes. That makes this type of fire unpredictable and potentially dangerous for firefighters who may not have been trained to deal with battery fires. 

More Water

A lot more water is required for EV fires than for conventional fires, Klock says. That’s because it’s critical for firefighters to lower the temperature of the burning lithium-ion cell. Conventional car fires can be smothered with water and foam, and they don’t usually reignite once they’re extinguished. With EVs, a battery fire may be inside a compartment that’s protected by shields, where the water isn’t directly affecting the flames. According to Klock, the point of fighting a battery fire is to lower the temperature to a point where the chemicals stop burning.

Fire departments have been encouraged to use thermal imaging to monitor the batteries even after the fire is out, according to a study prepared by the industry research firm Exponent for the Fire Protection Research Foundation.

“We’re gearing up to train more departments as we see more electric vehicles on the road,” Klock says. “The real issue is education.”

Departments are warned not to store a vehicle with a damaged battery within 50 feet of a building or another vehicle until the battery can be fully discharged. And the National Highway Traffic Safety Administration has advised fire departments to allow lithium-ion battery fires to burn themselves out if there’s no immediate threat to life or other property.

Tesla offers many of those same warnings to first responders in its Emergency Response Guide (PDF), in which the automaker advises that battery fires can take up to 24 hours to extinguish. The guide notes that “smoke or steam indicates that the battery is still heating,” and it urges that firefighters not release a vehicle to law enforcement officers or towing personnel until there has been no heating detected for 1 hour. A Tesla spokeswoman said the automaker had no comment on the NTSB report.

This investigation is just one of several automotive battery fires the NTSB has examined. In November 2011, the agency teamed up with NHTSA to look into a fire involving the lithium-ion battery in a Chevrolet Volt (PDF), where fire erupted on a vehicle three weeks after it underwent crash tests. From that investigation, NHTSA concluded that crash tests could compromise battery packs and lead to a fire, and that turning the EV upside down in rollover tests also could short out the batteries and cause a fire.

The NTSB is also currently investigating a fire involving a Hollywood director’s Tesla Model S on June 15 in Los Angeles. That incident drew a lot of internet attention after the director’s wife, “The West Wing” actress Mary McCormack, posted an eyewitness video on Twitter, showing bright orange flames shooting from under the front of the car, burning its tires and spreading quickly.

Lithium-ion battery fires aren’t new or unique to EVs. The NTSB and the Federal Aviation Administration have sounded alarms on lithium-ion battery fires in commercial aviation after some scary in-flight fires that were difficult to put out. Fires with Samsung’s Galaxy Note7 phone led to a high-profile recall. So-called hoverboards drew warnings (PDF) from the Consumer Product Safety Commission in 2015 and again in 2017, after the agency logged more than 250 fire or overheating incidents.

While EVs may pose challenges for first responders during fires, experts say there’s no reason for consumers to be any more concerned for their safety in an electric car than in a gasoline-powered vehicle. There are lots of ways conventional cars can catch fire, said Steven Risser, a researcher at Battelle Institute in Columbus, Ohio, who has studied electric-vehicle safety, in a report funded by NHTSA. There are hundreds of conventional car fires a day, compared with one every once in a while with an EV, he said.

The challenge of lithium-ion batteries in cars is that there hasn’t been nearly as much time to study the unique properties of battery packs, Risser said in an interview with CR. And when things go bad, there’s a chance for them to go bad in a dramatic fashion, he said.

Consumers shouldn’t panic or shy away from buying EVs because of the fire risk, which is still relatively low, Risser said. They’re better off concentrating on aspects of the car that are likely to yield more safety, such as better crash-test ratings, he said.

“We’re always consumed by the spectacular event,” Risser said. “If you’re playing the odds, you’re much more likely to be involved in a crash than a fire.”