Lithium-ion battery fires can be intense and scary. As someone who used to repair used smartphones, I've put out my fair share of burning iPhones with punctured lithium-ion batteries. And the type of smartphone battery you're carrying in your pocket right now is similar to the one found in electric vehicles. Except that an electric vehicle's battery stores a lot more energy—so much energy that some firefighters receive special training to put out the particularly intense flames that come from burning batteries after traffic accidents.
If you read the news about electric vehicles, you've probably come across many disturbing articles about the increasing number of battery fires. Recently, the U.S. National Transportation Safety Board and the California Highway Patrol announced that they were investigating a Tesla semi-truck fire that broke out after the vehicle hit a tree. The lithium-ion battery burned for about four hours.
Does this mean you should be concerned about fire risks with your electric car? Not really. It makes more sense to be concerned about a gasoline-powered vehicle catching fire than an electric car, since electric cars are less likely to catch fire than their traditional transportation counterparts.
“Fires caused by manufacturing defects in batteries are really very rare,” says Matthew McDowell, co-director of the Advanced Battery Center at the Georgia Institute of Technology. “Especially in electric vehicles, since they also have battery management systems.” The software monitors the various cells that make up an electric vehicle's battery and can help ensure that the battery is not stressed beyond its limits.
How do fires occur in electric vehicles?
If an accident occurs that damages the EV battery, a fire can occur due to a process called thermal runaway. EV batteries are not a solid building block. Rather, you can think of these batteries as a collection of many smaller batteries, called cells, pressed against each other. In thermal runaway, a chemical reaction in one of the cells ignites an initial fire, and the heat soon spreads to all neighboring cells until the entire EV battery is on fire.
Greg Less, director of the University of Michigan's battery lab, divides electric vehicle battery fires into two categories: accidents and manufacturing defects. He defines accidents as anything from a collision that damages the battery to a charging error. “Let's leave those factors aside for now,” says Less. “Because I think people understand that a fire can occur in an accident, regardless of the type of vehicle.”
While all electric vehicle battery fires are difficult to put out, fires caused by manufacturing defects are probably more concerning to consumers because they seem to occur at random. (Think back to when all those Samsung phones had to be recalled because they were a fire hazard due to battery problems.) How can these rare problems in the manufacturing of electric vehicle batteries cause fires at seemingly random moments?
It all depends on how the batteries are designed. “There was a flaw in the design that caused the cell to short-circuit, which then generates heat,” says Less. “Heat causes the liquid electrolyte to evaporate, creating a gas inside the cell. If the heat gets high enough, it catches fire, explodes, and then spreads to other cells.” These types of defects are likely the cause of the recent, highly publicized electric vehicle fires in South Korea that damaged over a hundred vehicles in a parking lot.
How to react if your electric vehicle catches fire
According to the National Fire Prevention Agency, if an electric vehicle catches fire while you are behind the wheel, you should immediately find a safe way to stop and get the car off the main road. Then turn off the engine and make sure everyone exits the vehicle immediately. Don't delay things by taking personal items, just get out. Stay at least 100 feet away from the burning car while you call 911 and request the fire department.
Also, don't try to put out the flames yourself. This is a chemical fire, so a few buckets of water won't be enough to smother the flames. For electric vehicle battery fires, first responders need about 10 times more water than for gasoline-powered vehicle fires. Sometimes firefighters decide to just let the battery burn out rather than extinguish it with water.
When an EV battery catches fire, the chemical fire can reignite after the initial fire has died down. It's even possible for the battery to flare up again days later. “Both firefighters and emergency responders such as recovery or towing companies must also be aware of the possibility that there may still be unused energy in the undamaged parts of the battery,” said Thomas Barth, an investigator and biomechanics engineer with the NTSB, in an emailed statement. “This energy can pose a risk of electrocution or cause the vehicle to reignite.”
While it may be tempting to return to the car and grab your wallet or other important items when the flame diminishes or goes out for a second, resist that urge. Wait for the local fire department to arrive to assess the overall situation and give you the all-clear. Staying far away from the car will also help minimize your risk of inhaling unhealthy fumes coming from the battery fire.
How could EV batteries be made safer?
In addition to quick recalls and replacements of potentially faulty lithium-ion batteries, the two researchers I spoke with were also excited about future opportunities to make electric vehicles even more reliable using a different type of battery, called solid-state batteries. “These batteries could potentially have greater thermal stability than lithium-ion batteries,” says McDowell. “When they get very hot, they may remain quite stable.” With a solid-state battery, the liquid electrolyte is no longer part of the battery cells, eliminating the most flammable aspect of the battery design.
These solid-state batteries are already available in some smaller electronic devices, but large-scale production of large versions of these batteries remains a hurdle that electric vehicle manufacturers are trying to overcome.
This story originally appeared on wired.com.