How do I make sure that my ebike battery won’t catch fire?

QUESTION: Read your review of the Specialized Turbo Creo SL 5.0. I am considering upgrading from my Specialized Sirrus 2.0; ten years old now. My hesitation is all the articles about e-bike batteries catching fire. Your opinion will be greatly appreciated. —Tony M.

RBR’S STAN PURDUM REPLIES: I understand and share your concern. I don’t want to burn my house down either. However, many reactions to e-bike battery fires are little more than gut responses and some veer into the realm of the paranoid. So this is my shot at a clear-eyed answer.

At the current state of technology, lithium-ion batteries are going to be powering our ebikes for at least a couple of more years, and even the best of those operate by means of a chemical reaction that produces heat. That said, given the great number of ebikes in use worldwide, and the relatively few number of fires related to ebikes, the fire threat has to be considered rare. See more here.

What’s more, within their limits, lithium-ion batteries are an efficient way to power ebikes. The demand for ebike batteries is exploding, and within the next 5-10 years, we may have solid state units that store power differently and are less likely to burn, but even before then, other chemical formulations may become available that offer lower burn risks. See more here.

Still, given that there is some risk, the current solution has two parts: 1) learn to shop for ebikes differently and 2) when you become an ebike owner, learn a set of practices that minimize the risk of fire.

Shop Differently

Experts in the ebike industry point out that cheaper ebikes and low-quality batteries — often imported from China — are more likely to explode than those that meet better manufacturing standards. That usually means you get what you pay for. In the current wild west of ebike manufacturing, you’re likely better off purchasing an ebike — or at least an ebattery — from a respected brand than from a new seller with the lowest price.

Especially with batteries, motors and chargers, you should look for the UL mark. That tells you that the equipment has met or exceeded the standards of the Underwriter Laboratories, a third-party certification company that’s been looking into safety matters on consumer items for about 125 years. Regarding ebikes, UL now has a protocol — UL 2849, the Standard for Electrical Systems for eBikes — that ebike equipment makers must meet to receive the UL mark.

The UL is not the only certification company, and it’s possible that equipment you are considering has been certified elsewhere. For example, the first ebike battery I had did not have the UL sticker but did have the CE mark, which shows compliance with the European Union Restrictions on Hazardous Substance requirements (usually abbreviated RoHS). While I haven’t tried to compare the two certifications, the EU mark did give me a measure of confidence in the battery (which, as far as I could tell, was made in China).

None of this is to say that a lower priced item without the UL mark might not work fine, but not letting price be the sole driver of your ebike decision and asking about UL certification of the equipment are both checkmarks in the “confidence” column.

Learn Best Practices

The manual that came with my Specialized Turbo Creo SL ebike, which I purchased new earlier this year, contained a few explicit instructions regarding charging the battery. One, which was repeated in two different sections, warned to use only the Specialized charger and the charger cord that came with the bike and not to use that charger on any other brand of ebike, even if the charger fit into the other battery’s port. Since I have seen similar warnings in the manuals of other ebike brands, I take this to be a universal rule.

The manual also said to make sure the charger’s socket and plug are clean and dry before connecting and charging the battery.

Also, one should not modify, open or disassemble the charger, nor should one allow it to overheat (some warming of the charger is normal, but it should not become so hot you cannot touch it). The charger should not be exposed to open fire or radiator heat.

Sheri Rosenbaum reviewed a special fireproof bag designed for charging ebike batteries that you might also consider.

Consumer Reports gives some additional recommendations:

• Do not leave an electric bike unattended while it’s charging, and don’t leave it charging overnight.
• If a battery overheats or you notice an odor, a change in shape or color, leaking, or odd noises, stop using it immediately.
• If the battery reacts in an alarming way, and it is safe to do so, move the device away from anything that can catch fire and call 911.
• Keep batteries and devices at room temperature. Do not place them in direct sunlight.
• Store batteries away from anything flammable.
• Do not use aftermarket batteries.
• Do not charge an electronic device under your pillow, on your bed, or near a couch.
• Do not block your primary way into and out of the building with an electric bike.
• Do not leave an electric bike in a child’s room or in any sleeping areas.

The idea of not leaving the battery charging overnight or where you cannot see it is based on the fact that some of the fires that have occurred started when the charging was unattended. There was no one around to quickly unplug them when something went awry.

That principle — keeping an eye on things — has applications in other areas as well. Lars Hundley, the RBR publisher, told me about a conversation he had with an attorney at a party who specialized in liability issues related to home fires. Her advice was never, ever leave your dryer running when you are not in the house, because that’s one of the most common ways people burn their houses down.

Will we all follow that advice to the letter when charging our ebike batteries? Possibly not, but we can at least avoid plugging the charger in and then forgetting it. When I charge my batteries, I set the alarm on my phone so that I return to check things every 45 minutes or so. I’ve never had the slightest problem while charging ebike batteries, so it’s tempting to assume there never will be, but I don’t allow myself to go there. 

Still, I look forward to solid state or whatever improved batteries are on the way. 

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Stan Purdum has ridden several long-distance bike trips, including an across-America ride recounted in his book Roll Around Heaven All Day, and a trek on U.S. 62, from Niagara Falls, New York, to El Paso, Texas, the subject of his book Playing in Traffic. Stan, a freelance writer and editor, lives in Ohio. See more at www.StanPurdum.com.