Mobile phones, laptops, cars and e-bikes burn or even explode. If you focus on the topic, you get the impression that batteries are more flammable than patrol tanks. What is your opinion on this topic?
Of course, bicycle batteries do have a hazard potential. This is always the case in technology with a certain energy density. And we simply don't have as much experience yet in dealing with the high energy density of large, modern batteries as we do with petrol engines, for example. Internationally, batteries with more than 100 watt hours are defined as hazardous goods. Bicycle batteries usually have 400 to 1,000 watt hours, much more than any laptop. That is certainly a potential risk. On the other hand, I have never heard of an e-bike battery exploding and injuring someone in a fall or accident.
If a battery ignites, is it more likely to happen during charging, on the road or in a parked bike?
In the vast majority of cases it happens during charging. On the manufacturer side, this is both a problem of the quality of the individual cells and one of the battery management system. Good chargers have sensors interacting with the battery controlling both the charge level of the individual cells and their temperature. Constant checking of the individual cells is important because a battery fire usually starts from a single overheated cell and then develops as a chain reaction through the entire battery. On the user side, it makes sense to store the battery for a while at room temperature before charging. Minus five degrees affect safety and durability, plus 50 degrees too - by the way, a good argument for easily removable batteries on the e-bike instead of batteries that have to be charged outside on the bike. What I would definitely rule out are aftermarket “quick chargers” and retrofit batteries of unclear quality. Greatest safety is provided by batteries and chargers from the same manufacturer.
A cyclist cannot simply check the quality of chargers and cells. But what can really everyone do?
Safe charging is crucial. I have already come across a case where a house burnt down because a battery had been loaded on the wooden workbench next to spray cans and solvents. There are three simple and effective ways to protect yourself: Firstly, the battery should be charged on a non-flammable surface. An old, large floor tile will do. Secondly, it is better not to charge the battery unattended overnight or leave it plugged in, but to charge it during the day so that you can react in the unlikely event of a battery fire - amateurs cannot do more than unplug it and then cool it with a bucket of water. The third safety measure is a smoke detector in the room, because fumes and smoke from a battery fire are quite toxic.
All in all, however, I see no reason for hysteria: I read the other day that one billion rechargeable batteries are put on the market worldwide every year. At least some of them are likely to be of lousy quality and run with poor battery management systems. But you really rarely hear about battery fires!
The interview was conducted by Jörg Spaniol
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