E-Bikes Are Going to Keep Exploding

Just past midnight on a Tuesday in June, a fire broke out in an e-bike repair shop in Manhattan. Sometime around midnight, an e-bike battery erupted into flames mid-charge. The blaze was quick and likely very, very hot. Firefighters responded within five minutes, but it was already too late: Flames spread to nearby apartments, killing four people.

It was not the first incident like this. New York City has been rattled by more than 100 battery fires so far in 2023, according to its fire commissioner, killing 13 people. In one incident in January, an e-bike or e-scooter battery caught fire and injured 18 children at a day care in Queens. Battery fires are not just happening in New York: From January 2021 to late November 2022, the Consumer Product Safety Commission received reports of more than 200 “fire or overheating incidents” and 19 fatalities, from 39 states, related to “battery-powered micromobility products”—industry jargon for e-bikes, e-scooters, and hoverboards.

America has an exploding e-transportation problem—and no easy way to fix it. Many e-bikes and e-scooters are perfectly safe, but bad batteries (and other bad hardware, such as chargers) at risk of igniting are making their way into some products. Policy makers are working on the issue, but no solution will arrive overnight. For the foreseeable future, more e-bikes will explode, and more people may die. “That’s the simple and horrifying truth right now,” William Wallace, the associate director for safety policy at Consumer Reports, told me. Unfortunately, when it comes to e-bikes and the like, we are stuck in a kind of battery purgatory.

If this problem has an epicenter, it’s New York City. New York’s density makes it particularly vulnerable to these fires. The city’s delivery workers often rely on e-bikes to do their job, because they are particularly useful in compact areas. And because millions of people live stacked on top of one another, fires can more easily spread between apartments there than in more sprawled cities such as Los Angeles (though a fire at an electric-scooter store in Venice Beach did kill one dog in March). But as e-bikes and e-scooters have taken off across the country, fires have been reported in other places, too, such as Virginia, Colorado, and Washington. Abroad, the London Fire Brigade says it has responded to one e-bike or e-scooter fire every two days so far this year.

E-bikes and e-scooters use lithium-ion batteries, which are everywhere—in our phones, in our laptops, in the Nintendo Switches we use to play Mario Kart. The vehicles are just the latest consumer products that use this technology to start spontaneously exploding. In 2006, Sony laptops were recalled after they started to combust. In 2017, it was Samsung Galaxy smartphones. In recent years, we’ve seen exploding hoverboards and vape pens and Teslas.

What makes the batteries so useful is also what can make them risky. “They put a lot of energy into a small little package,” Michael Pecht, a mechanical-engineering professor at the University of Maryland, told me. The batteries help us keep our smartphones powered for days without adding much bulk. They also can be strung together to power electric vehicles, letting us commute hundreds of miles on a single charge. Because they’re so energy dense, they’re also sensitive. Material between the positively charged “anode” and the negatively charged “cathode” keeps the energy separated. A small tear in the material can result in what Pecht termed “an explosive thermal runaway”—blistering heat in an instant, which can cause a battery to catch fire or blow up.

This sort of disaster scenario is not very common, to be clear. Reports of fires and explosions pale in comparison with how ubiquitous these batteries are. That’s because they can be—and frequently are—made well. Pecht told me that there are “very good” manufacturers and “very, very bad” ones. He has personally assessed facilities all over the world, everything from top-of-the-line businesses to low-quality “garage shops.” The southern part of China, he said, is home to a lot of the latter, though the country also has “some of the best manufacturing.” When it comes to battery sourcing, big, well-established companies such as Apple are going to use a reputable supplier.

Compared with other industries, the markets for e-bikes, e-scooters, and vapes are “more of the Wild West,” Pecht said, having so many manufacturers. Fancy e-bike companies might choose a best-in-the-business manufacturer for their products. But smaller or newer companies looking to make a quick buck may end up going with a sketchier manufacturer that isn’t producing batteries to industry safety standards (though the Consumer Product Safety Commission does not have mandatory requirements). For example, a low-quality manufacturer may go with a simple polymer separator; more expensive, high-performance batteries use a ceramic coating on top of the polymer to improve safety. And the fact that e-bikes are big puts them particularly at risk. “There are no other ‘cheap’ products with such large batteries, at least I cannot think of one,” Yushin told me over email. “The larger the battery size, the higher is the probability of something going wrong and causing a fire.”

Faulty batteries aren’t the only cause of e-bike or e-scooter fires. The device’s battery-management system—the hardware that connects to the battery, and the charger that plugs into it—also matters. “If you overcharge your battery, you can destroy it, effectively,” Gleb Yushin, an engineering professor at Georgia Tech, told me. A good battery and charger should prevent this from happening by shutting off when the battery reaches full power, but in some instances, it continues to fill with energy until it ignites. User error doesn’t help either. And e-bike owners may be unknowingly putting themselves at risk by using improper or cheap chargers, or by purchasing sketchy secondhand batteries. A Guardian investigation found inexpensive, unsafe chargers for sale on eBay, Amazon, and Wish.com.

Some simple precautions can go a long way. The National Fire Protection Association recommends buying only devices, batteries, and chargers that have been tested by an accredited lab; UL certification is the big one (look for the letters UL in a circle). People who have already purchased their bike can educate themselves on its specific hardware (actually read that manual). And be sure to charge it safely—using the charger that came with the battery—while it’s supervised. That means not leaving it plugged in overnight.

The obvious solution here would be for the CPSC to implement tougher standards. Wallace said that he would be “very disappointed and even more concerned than we already are if we didn’t see some sort of broad enforcement action this year.” It may not be that far off: The CPSC has called a meeting later this month to talk about lithium-ion-battery safety, with a focus on e-bikes, hoverboards, and e-scooters. A bill introduced in Congress would give the CPSC six months to create and implement such regulations. New York City, for its part, has already adopted a batch of new e-bike laws aimed at reducing risk, and late last month, the city announced that it will be adding safe e-bike chargers and storage to public-housing complexes around the city.

Still, no law can make the fire-prone e-bikes that have already been sold across the country suddenly disappear. And although standards help, they won’t prevent counterfeiting or the resale of used batteries. Eventually, Pecht thinks, we’ll shift to using different materials for high-density batteries, materials with less safety risk. But don’t hold your breath: Yushin said that he doesn’t think lithium ion will be supplanted anytime in the next 50 years. And the fact that so many types of devices caught fire before e-bikes likely means that e-bikes won’t be the last to ignite, either.

In the meantime, Pecht said that he’s fielding calls and emails almost every other day from the managers of apartment buildings whose residents are spooked about e-bikes. They wonder if such bikes are safe to store in a communal garage, for example. Pecht points out that the issue is bigger than just e-bikes: By that logic, you could argue, “Don’t have a vaping device in your apartment, because that could be a problem.” America’s battery challenges are complex. We want lots of power in a small package, and that involves some risk, whether the device is an electric scooter or a vape pen. Don’t be surprised if we’re stuck in battery purgatory for years to come.

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