How often do electric cars catch fire?

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Given the intense stories of electric vehicle fires and past disasters with lithium-ion cell phone batteries overheating, it’s reasonable to be concerned about an electric vehicle (EV) battery fire. But how often does this actually happen and why?

Do electric vehicles catch fire more often than gasoline cars?

Compared to how long gasoline-powered cars have been around, there isn’t a ton of data on EV fires at the time of writing. But there is enough to make some determinations. AutoinsuranceEZ compared data from several sources to try to find an answer to the question of how often electric cars catch fire.

Their sources were:

  • National Transportation Safety Board (NTSB)
  • Bureau of Transportation Statistics (BTS)
  • Recalls.gov

Per 100,000 vehicles sold, hybrids actually had the most fires and battery electric vehicles the least. As for the type of vehicle with the highest total number of fires, it was by far gasoline-powered cars. Recall data showed that a variety of components could cause a fire in a gas-powered car, but with electric vehicles and hybrids, it was almost always the battery.

Overall, electric vehicles had about a 0.3% chance of catching fire, while gasoline cars had a 1.05% chance of catching fire. This should be good news for EV owners, but as the AutoinsuranceEZ report points out, car fires are dangerous regardless of the cause.

Electric vehicle fires are rarer, but harder to put out

Although data shows that electric vehicle fires are rarer than gas-powered car fires, electric car fires burn hotter and for a longer period of time. In gasoline cars, there is usually only one reaction, like a spark in a puddle of gasoline, that leads to the fire and that reaction eventually dies out. When an electric vehicle’s lithium-ion battery ignites, the battery burns the energy stored inside, becoming the fire’s main source of energy and taking much longer to burn off.

Lithium-ion traction batteries are designed to pack a huge amount of energy into a very small space. Each cell inside is filled with a flammable electrolyte, as well as electrodes that could short out if damaged or improperly maintained, causing the cell to overheat.

If a cell overheats, it can enter a process called thermal runaway — basically, a positive feedback loop where it continues to heat up very quickly — and ignite neighboring battery cells until everything goes uphill. Lithium-ion batteries can also reignite after being turned off if moving them causes additional damage or new shorts in the battery.

Since first responders are primarily trained in extinguishing fires in a gas-powered car, they may find it difficult to extinguish an electric vehicle fire because it behaves differently. Instead of cooling the part of the car that a firefighter would normally do, he has to direct the water to the underside of the vehicle where the battery is. Stored energy that remains inside the battery, called stranded energy, can cause the battery to reignite hours or even days after the initial fire has been extinguished if this energy is not properly managed.

What can cause an electric vehicle fire?

Several factors can trigger a fire in an electric car, mainly related to the battery. If the battery is damaged in an accident, for example, it can cause a short circuit in one or more of the lithium-ion cells and trigger a chain reaction of thermal runaway.

If improperly maintained, the components inside the battery can degrade to the point that a malfunction could start a fire. Manufacturing defects can also be the cause of car fires, both in electric vehicles and gasoline-powered vehicles.

Age can also be a factor. There’s not enough data yet to show whether electric car batteries that are, say, 20 years old pose more of a fire hazard, but you have to be aware of that because components can degrade over time with a intensive use and poor maintenance.

Should you be worried about electric car fires?

The bottom line at the time of writing is that electric vehicle fires are much rarer than gasoline car fires. They are also much hotter, burn longer and can therefore be very dangerous.

This doesn’t necessarily mean that all electric vehicles are more dangerous than gasoline-powered vehicles, just that standardized safety guidelines need to be developed specifically to deal with these fires when they do occur. If you own one, make sure that you take great care in maintaining the components so that the risk remains low.

RELATED: Why does the battery of an electric car degrade?


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