Lithium-ion battery fires can be intense and frightening. As someone who used to repair second-hand smartphones, I've extinguished my fair share of flaming iPhones with punctured lithium-ion batteries. And the type of smartphone battery in your pocket right now is similar to what's inside of electric vehicles. Except, the EV battery stores way more energy—so much energy that some firefighters are receiving special training to extinguish the extra-intense EV flames that are emitted by burning EV batteries after road accidents.

If you've been reading the news about EVs, you've likely encountered plenty of scary articles about battery fires on the rise. Recently, the US National Transportation Safety Board and the California Highway Patrol announced they are investigating a Tesla semi truck fire that ignited after the vehicle struck a tree. The lithium-ion battery burned for around four hours.

Does this mean that you should worry about your personal electric vehicle as a potential fire hazard? Not really. It makes more sense to worry about a gas-powered vehicle going up in flames than an electric vehicle, since EVs are less likely to catch fire than their more traditional transportation counterparts.

"Fires because of battery manufacturing defects are really very rare," says Matthew McDowell, a codirector of Georgia Tech's Advanced Battery Center. "Especially in electric vehicles, because they also have battery management systems." The software keeps tabs on the different cells that comprise an EV's battery and can help prevent the battery from being pushed beyond its limits.

How do electric vehicle fires happen?

During a crash that damages the EV battery, a fire may start with what's called thermal runaway. EV batteries aren't one solid brick. Rather, think of these batteries as a collection of many smaller batteries, called cells, pressed up against each other. With thermal runaway, a chemical reaction located in one of the cells lights an initial fire, and the heat soon spreads to each adjacent cell until the entire EV battery is burning.