Firefighters thought they had extinguished the post-crash blaze. Then they heard popping sounds.
On the scene of a fatal crash involving a Tesla Model X in Mountain View, Calif., in March 2018, the fire department contemplated the energy hazards that lay in the wrecked electric vehicle before them. When further complications and potential dangers surfaced, the fire department called for help from the vehicle manufacturer.
In this case, it was fortuitous that Tesla’s headquarters was just across San Francisco Bay. In a matter of hours, two Tesla engineers had arrived at the crash site. But not every electric vehicle crash occurs in close proximity to industry-leading engineers.
As EVs proliferate, safety advocates and crash investigators are increasingly concerned about the risks lithium ion batteries pose to emergency responders.
In a report issued this month, the National Transportation Safety Board found vehicle manufacturers have given firefighters and other responders insufficient guidance on how to counter high-voltage battery fires and dissipate stranded energy, which can remain in batteries damaged in crashes and result in post-crash fires days or weeks after a collision.
First responders need to know “when it’s safe to transport the vehicle, how long they need to leave the road shut down, when it’s safe for a tow-truck operator to come and how to control risks for thermal runaway,” Kristin Poland, NTSB deputy director, tells Automotive News. “There are aspects of this where we feel the manufacturers have the best information and can help those emergency responders make good decisions.”
A review of the response guides for 36 models found that automakers provided vehicle-specific guidance on fighting battery fires in only two cases, according to the NTSB report.
The report does not delve into vehicle or battery designs; instead it concentrates on better protections for emergency responders in the aftermath of crashes and fires. It recommends manufacturers provide more specific information in emergency-response guides on mitigating thermal runaway, identifying stranded energy during a response and storing EVs with damaged batteries.
Further, the NTSB recommends that federal safety regulators consider a manufacturer’s adherence to ISO and SAE International standards when compiling emergency-response guides for EVs.
“This is very supportive of the fact fire service needs this training, and it’s critical they receive it,” said Michael Gorin, emerging issues program manager at the National Fire Protection Association. “The electrification process is continuing onward, especially with the new administration, and we need to continue to raise awareness and deliver this training.”
To date, the association’s training on EVs has reached approximately 250,000 firefighters. But that leaves the remaining three-quarters of the nation’s firefighting work force uncovered, not to mention law-enforcement officers, tow-truck operators and other responders.
“There’s a lot of work to be done,” Gorin said.
EVs account for only a sliver of the 170,000 vehicle fires that occur each year, according to the National Fire Protection Association, and there are no known instances of first responders suffering major injuries or being killed by battery malfunctions following crashes.
But the NTSB, the federal agency charged with conducting investigations into transportation crashes and forming safety recommendations, is concerned the dangers will grow as electric vehicles move into the mainstream.
Concerns over the use of lithium ion batteries in transportation began in June 2011, when a plug-in hybrid Chevrolet Volt caught fire in a salvage yard three weeks after undergoing crash tests. Two years later, the NTSB probed battery fires aboard a Boeing 787 in Boston and assisted in two international investigations into similar lithium ion fires on other aircraft.
“Whether that battery is in an airplane or car, it’s the same issue,” said Tom Barth, a survival factors investigator for the agency who worked on the aviation investigations and spearheaded this month’s EV report. “What it comes down to is, ‘If you have thermal runaway occur in a cell, how do you stop it from propagating from one cell to the next or from one module to the next?’ ”
The question persisted. An August 2017 crash in Lake Forest, Calif., involving a Tesla Model X brought renewed automotive concerns. Firefighters extinguished a post-crash fire but did not realize they needed to spray water onto the battery compartment underneath the vehicle. The battery experienced thermal runaway and reignited when a tow-truck operator winched the vehicle onto the tow truck.
The NTSB reviewed four cases in its safety report, and all four involved fires with Tesla vehicles in 2017 and 2018. But Poland stressed that the recommendations in the report should be heeded industrywide.
“We did not think as we started to go through this that it was a specific Tesla issue,” she said. “We felt like the safety issues that we identified were common to all electric vehicles, and we were seeing that through information we saw in Europe and other locations that were having problems extinguishing these fires with high-voltage lithium ion batteries.”
Perhaps nothing illustrates the complexity like the fatal Mountain View crash, one already familiar to NTSB investigators because the board had probed the role Tesla’s Autopilot played in the crash.
After arriving, Tesla’s engineers attempted to inspect battery components, but popping sounds again emanated from the battery, according to the report. They decided it was too risky to further analyze the vehicle along Highway 101.
Authorities needed a flatbed to avoid further stress on the vehicle structure. But it was metal, so they propped the Model X on wooden blocks. Six hours after the crash occurred, a fire truck escorted the flatbed from the scene and along an hourlong, uneventful ride to an impound lot.
When the Tesla engineers arrived, they underscored the importance of leaving a 50-foot radius around the vehicle. That was impractical, so the workers “did the best they could,” according to the report. Twenty minutes later, a California Highway Patrol officer heard popping sounds coming from the Model X, and the San Mateo Fire Department was summoned. Forty-five minutes later, they were called again. The battery had reignited.
Five days after the crash, the battery ignited one last time, and firefighters arrived to find flames 8 to 12 inches high.
“For me, that one was really eye-opening,” Barth said. “The fire department had access to the engineers, and there was still confusion about how to handle this vehicle and the attempts to remove the stranded energy; they were not able to do it effectively. That pointed to the fact that, ‘Hey, this stranded energy, there’s still gaps in the regulatory approach.’ ”
Despite the presence of two fire departments familiar with electric vehicles and two battery engineers from the vehicle manufacturer, the solution proved vexing, the risks resilient.