Kevin Noel spends his days selling electric bikes and scooters — and helping clients whose vehicles are misbehaving. He’s never had a problem with his own ride, a blue-and-white e-bike decorated with stickers, but he has heard the stories about electric-bike fires and seen his fair share of fried batteries.

“I charge it inside my house,” Noel, who works as bike shop assistant in Brooklyn, said of the bike’s lithium-ion battery. “I leave it on the charger overnight, and nothing ever happens.”

Lightweight lithium-ion batteries have become the norm in e-bikes and electric scooters, which power New York City’s massive delivery economy. If properly cared for, these power-packed batteries aren’t inherently dangerous. But they can cause exceptionally destructive fires if they’re broken, refurbished or stored improperly — particularly in bike shops or apartments with multiple batteries inside.

The frequency of fires involving the e-bike batteries is swiftly rising citywide. So far in 2022, the New York City Fire Department says it has investigated close to 70 such fires, including one fatal blaze. Between January and early May 2021, FDNY reported just 18.

If this pace continues, Daniel Flynn, chief fire marshal at the FDNY’s Bureau of Fire Investigation, expects twice as many e-bike fires this year compared to last.

“We’re not telling people not to get them,” said Flynn. “We just want to stress that they do present a danger and to be aware of that.”

Advocates said that delivery drivers need higher wages to afford better-quality batteries, safe places to charge and education on how to spot a dangerous battery. Usage data is hard to come by, but a report by Los Deliveristas Unidos counted some 65,000 New York City delivery workers in September 2021, most of whom use e-bikes to get around.

The bikes were legalized in 2020 after calls from cycling and delivery worker advocates. Experts say that between the increased reliance on delivery and the need for outdoor recreation, the pandemic pushed e-bikes’ popularity to new heights. Lyft has also gradually added more electric models to the Citi Bike sharing program.

“The tool is not the problem,” Hildalyn Colón Hernández, policy director for Los Deliveristas Unidos, a union for delivery workers, said of the bikes. “The tool is like a car. It’s how to use it safely. But that means education.”

Why e-bike batteries explode

Because they’re so much lighter than conventional batteries and can hold a lot of energy, lithium-ion batteries were a revelation for electric bikes, according to Mike Fritz, co-founder of Human Powered Solutions, a bicycle consulting firm. He should know: he’s been on e-bike engineering teams since the 1990s.

Fritz explained that lithium batteries contain a flammable liquid that conveys electrical current through its power cells. If the battery shorts and overheats, the fluid can ignite, creating a powerful fire with plenty of fuel.

“They burn hot, they burn smoky, they’re difficult to extinguish,” he said. “Imagine taking a butane torch and turning it on and trying to put out the fire.”

Cheap, damaged or refurbished batteries are more prone to these malfunctions, Fritz added. He says users should look for batteries that are certified by Underwriters Laboratories, which sets safety standards and tests units to ensure they comply.

Fritz and other experts said e-bike riders should charge their batteries far from flammable items like beds and couches — and away from an apartment’s main entrance so they can escape if the battery does ignite. They should also never leave their batteries charging unattended or overnight. Keeping the power storage units out of extreme heat or direct sunlight can prevent their overheating, too.

“The worst thing you can do is plug that thing in and walk away,” Fritz said.

Delivery drivers, who may ride their bikes for 10 or more hours per day in heat waves, snowstorms and other battery-straining weather conditions, are especially vulnerable. Their bikes and batteries endure an extraordinary amount of wear and tear, notes Dan Steingart, battery expert and professor of chemical metallurgy at Columbia University.

“Batteries have not been used in this context, in this way, at this scale, ever,” he said. “We’re sort of learning as we go here.”

Safer solutions

Advocates and experts alike point out that much of the conventional wisdom for e-bike battery safety isn’t practical for delivery drivers. Overnight charging, for example, is the only option for riders who spend their entire workdays out on the streets. And outdoor charging isn’t an option because of the risk of theft.

“Those batteries are essential for this workforce,” said Colón Hernández. “They’re not just using it to go for a ride.”

High-quality batteries can cost hundreds of dollars — too expensive for many delivery workers, who only make about $12 per hour, including tips, according to the Los Deliveristas Unidos report. They’re forced to use unsafe cheap or refurbished batteries instead.

In June, Los Deliveristas Unidos is planning on opening a hub where delivery workers can safely charge their bikes. They’re also leading trainings for drivers to help them keep their bikes in good shape and spot the signs of a battery on the brink — overheating, leaking, changes in shape or color, unusual sounds or odors.

Fritz also had some recommendations for bike shops, which can house dozens of batteries at a time. He said shop owners should invest in fireproof cabinets for battery charging and work with the fire department to figure out a fire safety plan.

Experts and advocates stressed that the fires are relatively rare considering how many e-bikes zip across city streets every day.

“The likelihood of a lithium-ion battery fire is minuscule,” Fritz said. “But when it does happen, it’s so potentially catastrophic that it’s worth precautions.”