Updated: Oct 19
After a rash of fires in New York this year, caused by e-bike and e-scooter batteries, the importance of battery safety has become deadly apparent. The health, financial and lifestyle benefits of cycling on an electric bike are only becoming more appealing but not at the cost of your home, or worse. The gears of government are slow to protect consumers, with dangerous poor-quality E-bike batteries being sold online with alarming frequency. How can we protect ourselves, our families and possessions, from ‘thermal runaway’ and the subsequent threat of fire that some lithium ion batteries pose right now?
Lithium- ion batteries currently make up the vast majority of e-bike batteries on the market. We won’t get too in the weeds on the chemistry/technical aspects of these batteries, but we will identify the primary causes of failure and go over what you can do to best mitigate each risk.
Physical damage to the battery may not be the first thing you think of when worrying about battery safety, but it is the aspect you have the most control over. If you do take a tumble on your bike, in many cases you may be completely fine. Just take the time to identify if there are any impact marks on the outer shell of the battery, as this could be an indication of internal damage. It’s also a good idea to bring it to a local shop for a safety check-up, not only for the electronic components but the regular bike parts as well. Also keep an eye out for any bulging on the battery after it may have taken impact, as this is often an indication of thermal runaway (which can lead to fire). A more common way that damage can occur to an e-bike battery is in a car collision with the bike on a car-rack. For this reason, we (and most e- bike manufacturers) recommend taking the battery off the bike and bringing it into the car with you as it’s much less likely to take direct impact this way. As an additional benefit, the bike will also be much easier to lift onto your rack without the extra weight of the battery.
Overheating, the second cause of failure we’ll cover, is also relatively easy to mitigate. Here in the pacific Nortwest, this is less of a concern than it might be in other climates. Even so, it is a good practice to keep your battery out of extreme temperatures when possible. The safe operating temperature for lithium ion batteries is -4℉ to 140℉. This is usually less of an issue while riding and more while in storage, where the battery cells can die completely if left in these extreme temperatures for extended periods of time. Our rule of thumb for our particular climate is: If you’re storing your bike for more than a month in a non-temperature controlled space, then bring your battery inside with you (ideally discharged to between 20% and 80%).
Overcharge is the most concerning of the three failure points we are bringing up. This is fresh in many people’s minds after the previously mentioned fires in New York. Overcharge, as its name suggests, happens when additional charge is attempted to be given to the battery after all of its cells are at full capacity. This can lead directly to thermal runaway, where cells self heat causing several unwanted effects, most concerning of which is fire. Surprisingly (or maybe not), this problem has already been more or less solved. E-bike batteries of reputable manufacture, generally have the ability to stop taking charge when it reads full capacity on its cells. Shoddy manufacturing, presumably as an attempt to lower cost, is the likely culprit in the majority of these fires. On the consumer side, the question of avoiding this issue essentially boils down to identifying batteries of higher quality build to mitigate risk. The most convenient way to identify batteries of quality, is to look for one of the UL certification logos on the battery itself. In doing this you’ll end up noticing that brands of good reputation, for instance Bosch, certify all of their electric bike batteries to UL’s highest standard (UL Listed). Anecdotally, we have also had little issue with batteries under the slightly lower standard of UL Recognized. Photos on this post give examples of these UL logos.
Hopefully additional consumer protections in the future will make this a moot point and no outwardly dangerous batteries will be allowed to be sold to consumers in the first place, but until then, hopefully this has helped in your e-bike search, or put your mind at ease with your current e-bike. The additional safety standards required to get these certifications on batteries do increase the price of the batteries, but it is more than reasonable when considering the danger they pose under the current lack of regulation.
Our shops take battery safety very seriously. It is a consideration when bringing in any new electronic system. We are not only salespeople and mechanics, but riders of the same bikes, so we spend a considerable amount of time curating what bikes we bring in at any given time to create a lower barrier to entry and more peace of mind in purchasing. We hope you’ll stop by for a guided test ride and a chat if you’re in the greater Seattle area.
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