What firefighters need to know about electric car batteries

Understanding how they are made and what happens when they fail will keep firefighters safer at electric-powered car fires


On June 26, 2020, astronauts Chris Cassidy and Bob Behnken performed an extravehicular activity to swap out three aging nickel-hydrogen batteries for two more efficient lithium-ion batteries on the International Space Station (ISS). While I’m not an expert on space travel, since these batteries are housed on the exterior of the ISS, the use of lithium-ion batteries would be safe since there is no atmosphere in space to support combustion. Such is not the case with some lithium-ion batteries here on earth.

Traveling through any major airport, you might have heard the boarding gate personnel give a warning to all passengers from the Federal Aviation Administration stating that travelers can bring a Samsung Galaxy Note 7 phone on the flight with them, whether in the cabin or in checked luggage.

Most airlines also advise you not to bring anything with lithium-ion batteries, including any e-cigarette device, on your person or in checked bags.

A screenshot from a YouTube video shows a Tesla Model S on fire as a result of a battery fire.
A screenshot from a YouTube video shows a Tesla Model S on fire as a result of a battery fire.

The airlines themselves have had some negative experience with lithium-ion batteries used in the auxiliary power unit of the Boeing 787 Dreamliner. On at least four occasions early into the use of this aircraft, these batteries suffered what is referred to as “thermal runaway,” in which the heat from a failing cell causes itself and surrounding cells to fail, thereby generating more heat. In some instances, the units experienced enough heat to catch nearby combustibles on fire causing smoke in the cargo space or in the passenger cabin.

Following several residential fires across the country caused by lithium-ion batteries, including one in my department's jurisdiction, the concern over personal items using lithium-ion batteries prompted the NFPA to issue a tip sheet entitled “Lithium-ion Battery Safety for Consumers” on the use of such items as hoverboards, children’s scooters, remote-control gadgetry, laptops, toys, smartphones, e-cigarettes and even the 10-year batteries in smoke alarms.

The tip sheet cautioned that lithium-ion batteries store a large amount of energy in a very small space, are designed for specific uses, and like any other manufactured item can be subject to defects that cause the batteries to overheat, catch fire or explode.

The NFPA warned to cease using the item if a consumer noticed a strange odor, change in color, excessive heat, a change in the shape, leakage or odd noises coming from the consumer item.

Car batteries

The issue of lithium-ion batteries is not new to the NFPA. Many years ago, it began to look at the issue of lithium-ion batteries in electric cars. This research included a series of tests on vehicles with lithium-ion batteries. One of their conclusions was clearly stated in the following excerpt from that report:

“In each of the six full-scale burn tests, firefighters at the test site found that they needed to flow large amounts of water on the batteries, because fire kept flaring up even after it appeared to be extinguished. In one test, a battery fire reignited 22 hours after it was thought to be extinguished.

“Everything looked normal,’” recalled Andrew Blum, a researcher at the firm Exponent, which conducted the tests. ‘When we looked at the battery through a thermal imager, everything was back to ambient temperatures; the fire was extinguished as we would define it. But there was something going on internally in the module, and we just couldn’t tell.’ In two of the tests, firefighters ran out of air and had to switch tanks because of the length of time it took to fully extinguish the battery, according to Blum.”

While more and more products are being manufactured with lithium-ion batteries, their use in electric cars and other vehicles may currently be of the most concern to the fire service. Several years ago, I analyzed a crash and double fatality in Indianapolis of a Tesla S P85 and the issues Indianapolis firefighters found upon arrival.

Another Tesla S P85 reportedly crashed, this time in Australia along their major Pacific Highway. While this crash was not fatal, the Australian news media reported that it “closed the highway in both directions as emergency crews worked to pick up thousands of AA batteries … the front battery pack rupturing, spilling the batteries across both lanes.”

This media report caused me some grave concern for the Australian firefighters at the scene since they must have noted that the individual 18650A Tesla battery cells were larger with a wider cylindrical diameter than ordinary AA batteries.

Hopefully these firefighters realized something was different and took their time to research the Tesla Emergency Response Guide that included safe handling and disposal of these battery cells. The media report was sketchy at best, and did not shed any additional information on those details.

Understanding lithium-ion

Independent of the potential poor workmanship in the construction of lithium-ion batteries used in personal devices, in a crash involving an electric vehicle, if the metal housing shielding the lithium-ion batteries is breached, oxygen in the air can speed up the “thermal runaway” process, especially if the individual cells are damaged and scattered about the wreckage.

I discussed some of these issues with Celina J. Mikolajczak, Tesla Motors’ senior manager for cell quality and materials engineering. Mikolajczak also took part in the earlier NFPA research and helped author the Phase I Report, "Lithium-Ion Batteries Hazard and Use Assessment," which was designed to help assess the flammability of these batteries in storage facilities and how they could be controlled by automatic sprinklers with regard to the NFPA 13: Standard for the Installation of Sprinkler Systems.

Mikolajczak said that lithium-ion is a lithium-salt-based solution and not lithium metal per se. Specifically, the Tesla batteries are battery cells that are separately encased and have an ethyl-glycol (anti-freeze) coolant that independently cools each cell. The cooling system is designed so that, under normal operating conditions, if one cell would go into thermal runaway, it would not begin a chain of thermal reactions from one cell to another.

The takeaway from the experts, and from the experience of the Indianapolis Fire Department, have prompted me to suggest some guidelines for firefighter safety, not only for working on vehicles with lithium-ion batteries but also any fire in an alternative-fueled vehicle.

  • Wear full PPE and SCBA
  • Identify the type of vehicle involved — standard vehicle, EV, HEV, HF, etc.
  • Use a thermal imaging camera to help with the 360 size-up
  • Establish an appropriate incident command structure
  • Establish tactical priorities (fire, extrication, victim care)
  • Stabilize the vehicle
  • Power down, if possible
  • Secure a large, continuous and sustainable water supply — one or more fire hydrants or multiple water tenders
  • Use a large volume of water such as master stream, 2½-inch or multiple 1¾-inch fire lines to suppress and cool the fire and the battery
  • Consider that this could be a combined fire, extrication and hazmat incident
  • Have sufficient fire personnel and apparatus on scene for an extended operation to monitor the battery’s heat or possible re-ignition
  • When turning the vehicle over to a wrecker or towing company, brief their personnel on the hazards
  • If possible, follow the wrecker to the storage area, and place the battery-powered vehicle in a space away from other vehicles, buildings or combustibles

Several training guides are available on line including the Tesla website or NFPA’s several online training programs. Other alternative fuel programs are available here.

2016 Models S Emergency Responders Guide

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