Fires in electric vehicles regularly stir social media. However, a battery-powered car has much less risk of catching fire than a thermal vehicle. If the fire is sometimes overwhelming, the emergency services have specific intervention procedures.
Jets of sparks, crackles, thick smoke: the conflagration of an electric vehicle battery can be impressive. However, you are unlikely to see one in your lifetime. Do electric cars catch fire more often? No ! Electric cars pose less of a fire hazard than their gasoline and diesel counterparts.
A study published in early 2022 by American insurer AutoInsurenceEZ demonstrated this in particular. A ratio of 25 fires/100,000 electric vehicles was found, against 1,529 fires/100,000 thermal vehicles and a surprising rate of 3,457 fires/100,000 hybrid vehicles.
Why can an electric car battery light up?
A battery can catch fire for a variety of reasons. Puncture, displacement, deformation or a simple malfunction of the BMS (the computer that regulates energy flows in the battery) can cause a short circuit and then thermal runaway of the cells, leading to a localized or generalized fire.
Most battery fires appear to be caused by a design or manufacturing defect. Bugs fixed quickly during extensive recall campaigns, such as those for the Hyundai Kona, or by remote upgrades, such as those carried out by Tesla after a series of fires.
Side impact protection
Traffic accidents are more rarely the cause of battery damage. If the tank of a gasoline or diesel vehicle can burst during an impact, it is more difficult for a battery that is protected by a metallic structure. Battery displacement cases refer only to extremely violent accidents and do not systematically involve a fire.
A package is, however, more likely to be punctured during a vertical impact and concentrated under the vehicle, with the horizontal surface facing the road being its Achilles heel. In this case, cell compartmentalization may contain leakage to the affected area. Also, an eviscerated battery does not leak large amounts of flammable liquid, unlike a fuel tank.
Is an electric car battery fire dangerous?
Like all fires, a battery fire is naturally dangerous. Obviously, it is necessary to evacuate the vehicle without delay at the slightest smoke or suspicious phenomenon. However, the absence of highly flammable fluid reduces the risk of damage from spreading through spillage. A battery contains solid or gelled materials that will burn on the spot.
According to a test carried out in late 2021 by the Austrian fire department, the universities of Graz and Leoben, as well as the consultancy ILF Consulting, an electric car fire (considering the entire vehicle and not just its battery) releases a little more heat than a fire in a diesel car. The latter measured between 6 and 7 megawatts (MW) the average “thermal load” of an electric, when a diesel releases about 5 MW. A rather small difference that would not cause a significant increase in risk to users, according to firefighters.
How do firefighters put out an electric car battery fire?
Emergency services had to adapt to the arrival of electric vehicles on the market. New protocols and materials are regularly introduced to quickly and safely contain a battery fire. A massive supply of water is always recommended, as in a thermal vehicle. “If the high voltage battery catches fire, is exposed to high temperatures, or is bent, twisted, cracked or broken in any way, use large amounts of water to cool the battery” therefore recommends Tesla.
Electric cars are designed to cut power immediately upon impact. To avoid any risk of electrocution, firefighters can manually remove the main circuit breaker or use a dedicated plug to plug into the vehicle’s charging port. This tool also prevents accidental starting, for example, if the driver presses the accelerator pedal.
To act more effectively on runaway batteries, rescuers can also get a special spear. Equipped with a punch, it allows to pierce the package to inject water directly at high pressure.
Finally, firefighters can use a thermal camera to identify hot spots and ensure the disaster is completely extinguished. In some cases, the battery can be kept under observation for several tens of hours and, more rarely, immersed in a container filled with water. As with a heat engine fire, the extinguishing water is loaded with pollutants. They must be collected by settling ponds normally located along roads.