Electric car batteries are catching fire and that could be a big turnoff to buyers

(CNN) -- Automakers seeking to forge ahead in the electric vehicle market have been hitting a bump in the road recently: batteries keep catching fire.

At the end of September, BMW initiated a recall in the United States of 10 different BMW and Mini plug-in hybrid models because of a risk of fire caused by debris that may have gotten into battery cells during manufacturing. Then, in early October, the National Highway Traffic Safety Administration opened an investigation into reports of apparently spontaneous battery fires in Chevrolet Bolt EVs. GM says it is cooperating with the investigation.

A few days later, Hyundai announced that it was recalling 6,700 Kona Electric SUVs in the United States, among about 75,000 of that model to be recalled worldwide, after it had received numerous reports of vehicles catching fire while parked.

By all indications, electric car battery fires remain infrequent occurrences, even compared to gasoline and diesel fires. But they get attention because electric vehicle technology is still considered relatively new.

And that has the potential to turn prospective buyers away from the burgeoning market for electric cars, said Michelle Krebs, director of automotive relations at AutoTrader.

AutoTrader's parent company, Cox Automotive, regularly surveys car shoppers about their priorities when lookingfor a new vehicle and the top two are always dependability and safety, Krebs said. Reports of vehicles catching fire are obviously bad on both counts.

"There will be a full court press for the automakers to get a handle on this because this is their future market and they need to address it and they will," she said.

Tesla faced this last year aftertwo highly publicized battery fires, which spurred it to update its vehicle software. Years earlier, after a car fire caused by battery damage from road debris, Tesla added plates underneath its cars to better protect the batteries.

Why batteries burn

Lithium-ion batteries, whether they're in cars, smartphones or automobiles, cancatch fire if they've been improperly manufactured, damaged or abused or if the software that protects the battery from getting too much or too little electric charge failed to do its job, said Ken Boyce, principal engineering director at the product safety and testing group Underwriters Laboratories.

Fortunately, when you consider how many lithium-ion batteries there are in the world today, battery fires are pretty rare.

"It's been estimated to be about one in 12 million. So that's quite favorable," said Boyce. "There's a couple of caveats on that, though. As we see four to six to eight billion [lithium-ion battery] cells going out each year, that one in 12 million, that starts to get up there."

Battery cells are the individual small batteries that, in an electric car, are put together inside a battery pack. An electric car can have hundreds or even thousands of battery cells inside one or more battery packs.

Consumer demand for electricvehicles that can drive farther before needing to recharge have led manufacturersand researchers to seek ways to make batteries that store more energy. The goal is to do this without making battery packs bigger and heavier. That means increasing energy density, or the amount of energy that can be stored in a given amount of battery space.

This can be done in a number of ways, but it has to be done while adhering to accepted industry safety standards because more energy in the battery means more energy potentially spilling out of control if something goes wrong.

"It's not that the energy density going up makes it more dangerous," said Boyce. "It just means that it's that much more important to make sure that safety is really holistically and very effectively managed."

Gasoline also burns

Gasoline-powered cars can also catch fire, of course. That shouldn't be surprising since combustion is central to how they work. They carry around containers of highly flammable liquids, they have engines that get very hot and electrical equipment that can make sparks. Still, car fires remain relatively rare and have been getting rarer. But it's hard to fairly compare the numbers of gasoline fires to electric car battery fires.

In 2018, the most recent year for which statistics are available, there were about 181,500 "highway vehicle" fires reported in the United States, according to the National Fire Protection Association. The vast majority of these would have been in gasoline- or diesel-powered cars or trucks.

Nowhere near that many electric vehicles would have caught fire that year. But, of course, there are far fewer electric and plug-in hybrid cars on the road. Fires become more likely as vehicles age, noted Marty Ahrens, a research manager at NFPA, and most electric cars on the road today are still very new.

It's also important to note that people haven't stopped buying gasoline cars despite the obvious risk of fire, pointed out Matt DeLorenzo, senior executive editor at Kelley Blue Book. And, as they see more and more electric cars being driven by friends and neighbors, they probably won't be deterred from buying an electric car based on a relative handful of reported incidents.

"If it's something that is fairly isolated, even though they're studying it, but it's not every car is catching on fire, then I don't think it'd be a problem," he said.

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