Lithium-ion battery fires are intense and scary. As someone who repairs used smartphones, I’ve pulled out quite a few burning iPhones with punctured lithium-ion batteries. And the smartphone battery you’re carrying in your pocket right now is similar to the one in an electric car. Except that EV batteries store a lot more energy—so much so that some firefighters are specially trained to put out extremely intense EV fires that occur after an EV battery catches fire following a road accident.
If you’ve been reading the news about EVs, you’ve probably seen a lot of scary stories about the rise of battery fires. Recently, the National Transportation Safety Board and the California Highway Patrol announced that they were investigating a Tesla semi-truck fire that started after the vehicle hit a tree. The lithium-ion battery burned for about four hours.
Does this mean that you should be concerned about personal electric vehicles as a potential fire hazard? Actually, no. It makes more sense to worry about gas-powered vehicles burning down than electric vehicles, because EVs are less likely to catch fire than traditional vehicles.
“Battery fires due to manufacturing defects are really rare,” says Matthew McDowell, co-director of Georgia Tech’s Advanced Battery Center. “Especially in electric vehicles, because they also have battery management systems.” That software can help keep track of the various cells that make up an EV battery and prevent it from exceeding its limits.
How do electric vehicle fires occur?
In a crash that damages an EV battery, a fire can start with what is called thermal runaway. An EV battery is not a solid brick. Instead, think of it as a bunch of smaller batteries, called cells, pressed together. With thermal runaway, a chemical reaction in one of the cells starts an initial fire, and the heat quickly spreads to each adjacent cell until the entire EV battery is burned out.
Greg Les, director of the University of Michigan’s Battery Institute, divides EV battery fires into two distinct categories: accidents and manufacturing defects. He considers accidents to be anything from a crash that punctures a battery to a charging error. “Let’s leave that out,” Les says. “I think people understand that if you have an accident, regardless of the type of vehicle, you can have a fire.”
While all EV battery fires are difficult to extinguish, fires caused by manufacturing defects can be more concerning to consumers because they occur randomly. (Recall when Samsung recalled all its phones because of a battery issue that posed a fire hazard.) How can such a rare problem with EV battery manufacturing cause fires at seemingly random moments?
It all depends on how the battery is designed. “Somewhat misengineered, the cells short out, and then they start to heat up,” says Less. “The heat causes the liquid electrolyte to evaporate, creating gas inside the cell. If it gets hot enough, it can catch fire, explode, and spread to other cells.” This type of defect is likely responsible for a recent spate of high-profile EV fires in South Korea, one of which damaged more than 100 cars in a parking lot.
What to do if your EV catches fire
According to the National Fire Agency, if your EV catches fire while you are driving, immediately find a safe way to pull over and pull away from the main road. Then, turn off the engine and have everyone get out of the vehicle immediately. Do not delay the work by gathering personal belongings and just getting out. When calling 911 and requesting the fire department, stay at least 100 feet away from the burning car.
Also, you should never try to put out the fire yourself. This is a chemical fire, so a few buckets of water won’t be enough to put out the fire. An EV battery fire can be extinguished by emergency responders using about 10 times more water than a gasoline vehicle fire. Sometimes firefighters may decide to let the battery burn out on its own without spraying water.
If an EV battery catches fire, the chemical fire can re-ignite after the initial combustion has died down. The battery can even burst into flames again days later. “Both firefighters and secondary responders, such as vehicle recovery or towing companies, need to be aware of the potential for isolated energy remaining in undamaged parts of the battery,” NTSB investigator and biomechanical engineer Thomas Bass said in an emailed statement. “This energy could create an electric shock hazard or cause the vehicle to catch fire again.”
As the fire diminishes or goes out for a moment, you may want to go back into your car to grab your wallet or other important items, but resist the urge. Wait until your local fire department arrives to assess the situation and tell you it is safe. Staying away from your car will also help minimize the chance of inhaling harmful fumes from a battery fire.
How can we make EV batteries safer?
Beyond the rapid recall and replacement of potentially defective lithium-ion batteries, the two researchers I spoke with were excited about the future possibilities for another type of battery, solid-state, that could make EVs more reliable. “These batteries have the potential to be more thermally stable than lithium-ion batteries,” McDowell said. “They can heat up quite a bit and still remain quite stable.” In a solid-state battery, the liquid electrolyte is no longer part of the battery cell, eliminating the most flammable aspect of battery design.
While these solid-state batteries are already available for some small electronics, producing them in large quantities remains a hurdle that electric vehicle manufacturers are working to overcome.
This article originally appeared on wired.com.
