Even before gas prices hit all-time highs, the best electric bikes and electric scooters have become increasingly popular ways of getting around. But, their increased presence has brought with it an increased danger of fires, both from uncertified batteries and from improper charging and storage.
In New York City, for instance, there were 18 deaths as a result of fires from lithium-ion batteries, which prompted the city to implement stricter regulations on the sale of e-bikes — and specifically, their batteries. As a result, the number of e-bike fatalities from fires in the city dropped to just one in 2025.
But, there are dozens upon dozens of ebikes and electric scooters for sale on Amazon and other online retailers, so how do you know which bikes are safe, and which pose a potential hazard? And, once you buy an e-bike, how to you properly store and recharge its battery?
To find out, I talked to Dr. Robert Slone, the Senior Vice President and Chief Scientist for UL Solutions, which regularly tests and certifies thousands of products each year to make sure they’re safe for consumers.
Rob leads UL Solutions’ innovation in safety, security and sustainability science. As senior vice president and chief scientist, guides UL Solutions in advancing scientific innovation and technical expertise across sustainability, safety and security.
What should shoppers look for when buying an e-bike?
We can only speak to our certification, but what they can look for in terms of a UL-certified e-bike [UL 2849] is the UL mark, the U and the L in the circle. For e-bikes, we've gone a step further. We apply a holographic label, which is much more difficult to fake or to counterfeit. And that is typically placed either, and or I guess, on the battery pack and or the bike frame. So it's visible and it's pretty easy to see.
What are some of the tests that you put a battery through?
If your ebike or scooter has been certified by UL Solutions, it should have a sticker on it somewhere. However, you can also look up products at UL Solutions database.
We do a full range of tests in terms of overcharging. We test the battery management system, which is like the software system of the battery. We address environmental concerns in terms of hot and cold conditions, water exposure.
I live in the New York City area and the streets are not always the smoothest, to say the least. So vibration testing, drop testing, shock testing, those sorts of things are also part of what we do, both for the battery and then also for the bike itself, for the frame and the motor and those sorts of components.
We look at aging and cycling of the battery. Is it showing signs prematurely of overheating or aging and danger signs like that? And then electrical elements like overcharging the battery also play a role.
And then basics on the design manufacturing. What's the quality of the manufacturing? Do you see metal bars and sharp edges, whether on the frame in the bike or in the battery itself?
Once someone gets an e-bike, what are some tips for charging it safely?
The first thing to know is that this is a system. It's the battery, the bike, and the charger. In the New York area we've had a difficult journey with e-bikes, to say the least. One fire in Astoria [was caused when] an e-bike was paired up with a mismatched charger, an aftermarket charger that was never designed for that e-bike. It caused the battery to go into thermal runaway.
Make sure you're using either OEM original battery and charger or OEM approved battery and charger.
So if you were to lose your charger, you shouldn't just go into Amazon and find a charger that says ‘compatible with whatever.’
No, I would go back to the original OEM site or call them or get the information or go back to the place where the bike was purchased to ask the question and confirm which chargers are designed to work with that e-bike. There's no universal charger out there. That's not something that exists today for this segment of products.
It's not like recharging a phone.
Definitely not like that. You know, and even for phone charging in the earlier days and even today, you can get into trouble. But e-bikes, it's actually not uncommon to have that be a source of a charging issue or a fire during charging is that these things were never designed to work together.
Any other tips?
One of the other things in safely charging a battery in an e-bike is to pay attention to where that's happening. This is where I give a lot of credit to our sister organization, the Fire Safety Research Institute.They've done a lot of public outreach to tell people, please, please, please do not put your e-bike at the one and only entrance and exit to your apartment.
Because if you do that, you plug it into the wall and you go to sleep, these are explosive fires, and you're not going to be able to respond in time to it in all likelihood. And that has been, again, a source of many of the tragedies and really severe outcomes.
What are some other sort of common mistakes that people make when charging batteries?
I think ignoring some of the signs, like swelling of the battery. If you see outgassing, then that's actually time to either remove the bike from its current location. You really, really need to be aware that that battery is in its last moment, so to speak, if you're seeing outgassing. The overheating and swelling usually come first, and that's when you really want to go on and replace the battery before it even gets to that outgassing point.
Should you charge a battery to 100%?
There should not be a problem with charging a battery to 100%. The reason I say that is because the battery management system, the BMS or software, is designed to tell the user if there's a problem. The bike will stop short of 100% charging if it's overheating, provided the BMS is functioning properly. Part of our testing and certification process is to check the software that it is functioning correctly and shuts the charging process off if there's a problem.
In fact, that is also one of those signals that if it's not making it to 100% or your BMS is warning you along the way, it's warning you. So you need to kind of take a closer look at that and understand, is the battery starting to deform? Is the battery hotter than it should be or hotter than it's been earlier in the life of that bike or that battery pack?
If you're going away for a vacation, what are some steps that you should do to make sure you've safely stored your ebike or scooter?
If you're going to be away for a long time, there are a couple of basics. To the extent [you have] storage space that's away from flammables, that's a good basic rule. Do not keep the device charging while you're away. Do not keep it charging unsupervised.
The lower the charge state — if you can discharge or use up [the battery] — before you leave, that's better. In fact, many of these devices are shipped in a lower charge state. So I think following that type of guidance is a good way to ensure that while you're away, nothing really big is going to happen with that device.
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