EMTB 02/2020

Fire risk

Again and again we hear about rechargeable batteries that caught fire and caused considerable loss. How great is the danger really?

Hanover, Weil am Rhein, Mainz, Bad Vilbel. In all these German cities there have been fires in recent months which the fire brigade attributed to e-bike batteries that had caught fire. Are pedelec batteries really as dangerous as that? How come that a rechargeable battery catches fire just like that? First of all: A rechargeable battery does not catch fire just like that. If it does happen, however, it is usually due to a short circuit in the battery because the separator, which is a membrane that separates the cathode and the anode in a battery cell, sustains damage. This happens, for example, when the battery cell expands uncontrollably in hot weather, when the ion transport through the separator is paralysed due to excessive cold, or when the separator is damaged as a result of a forceful impact. The escalation then almost always occurs during charging. Since an e-bike battery consists of a large number of battery cells due to its high capacity, the probability of a defect is somewhat higher than in the case of a smartphone, for example. All in all, however, it is still very low. We asked the bicycle expert Dirk Zedler how he assesses the risk of rechargeable batteries catching fire.

Graduate engineer Dirk Zedler, sworn expert for e-bikes
In my experience, the problem is much more often caused by a defective socket, the charger or the user than the rechargeable battery itself. I can therefore only advise you to act with a certain amount of circumspection. Do not charge or store the battery in heat or freezing cold, avoid deep discharges, do not use externally damaged batteries and use batteries from well-known manufacturers such as Bosch, Panasonic or BMZ. These manufacturers simply have the most experience in the field of battery management and are therefore the safest. And last but not least: Keep away from battery refurbishing, i.e. the recycling of an old battery.

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