How dangerous are e-bike batteries? – BIKE IMAGE

It’s the horror of e-bike riders: when charging, the battery suddenly catches fire. The flames leap over and set the house or apartment on fire. Although this scenario is not very likely, it cannot be ruled out. Fires caused by batteries in bike shops and homes regularly make the news.

The flames and even explosions in the test show how much energy is in the batteries.

Risk factor battery cells

The good news first: The chances of something like this happening to you of all people are very low, the product experts from the Dekra testing institute assure us after the testers have examined the potential danger of defective e-bike batteries. According to statistics, the general risk with millions of electric bicycles is only in the per thousand range. But what can happen in the rare case of a damaged battery pack is dramatic. During the controlled test under the supervision of the fire brigade (impacts, falls and punctures), there were powerful explosions with fragments flying meters and flames that shot out of the energy cells. It is particularly problematic that batteries used in pedelecs can catch fire again and again. This is because it is not a single battery, as one might like to believe, but battery packs in which many lithium-ion cells are connected together, which ignite each other and thus accelerate the fire. E-bikers should therefore have the potential danger on their radar.

Caution hot! Batteries that have long since burned out still pose a risk.

The correct handling of e-bike batteries

In order to keep the risk as low as possible, the product experts recommend adhering to all tips and recommendations for handling the energy sources. Batteries should be checked regularly by a professional as part of routine bicycle maintenance. Possible errors in battery management, which regulates the distribution of energy between the cells, can be identified quickly.
In addition, you should not charge the batteries longer than necessary, at best not overnight. If you are unsure, you should also load on a fireproof surface away from easily flammable objects and be nearby in case something happens. In principle, it is also true that you can trust batteries from well-known bicycle brands more than those that are installed in cheap bikes.

If the battery pack of an e-bike is severely attacked, it will immediately catch fire

Our most important tip: Batteries that have been dropped or damaged should never be charged or used, but must be checked by qualified personnel and replaced if necessary.

A nail puncture simulates damage to a battery cell.

The most important questions and answers about e-bike batteries:

How do I charge the e-bike battery correctly?


Lithium-ion cells can be charged for any length of time, regardless of their state of charge. In conjunction with the charger, the battery management system (BMS) protects the battery from overloading when charging. Interruptions in the charging process do no harm. On the contrary: Manufacturers recommend frequent partial charges, which should have a positive effect on the service life. Important: Rechargeable batteries should only be charged with the associated charger. Otherwise irreparable damage may result. Battery expert Stefan Scheuer adds: “The battery doesn’t like charging when it’s warm and discharged. I don’t charge my battery continuously at night, nor do I charge my smartphone. This is about functional reliability and the question: how safe can devices be detect the end of charging? A charger and the BMS must detect when the battery is charged. The charger can have a source of error, and if a battery’s BMS also fails, it will continue to charge and it can explode. I don’t take that risk “But there is a solution for that: a timer. Then the battery may only be 90 or 95 percent charged, but that doesn’t matter and is even beneficial for the service life.”

How do I store my e-bike battery correctly?


If the e-bike is not used for a long time, the battery should be stored dry, cool and with 30 to 60 percent of the charging capacity. We recommend checking the state of charge every two months.

What should I watch out for with e-bike batteries in winter?


Cold reduces the performance of the battery. At temperatures below zero degrees Celsius, it is advisable to insert the battery that has been charged at room temperature shortly before setting off. When the outside temperature is ten degrees or more, experts recommend taking the battery into the warmth.

What should I watch out for with e-bike batteries in summer?


In summer, the battery should be protected from direct sunlight as much as possible.

How do I prevent deep discharge in e-bike batteries?


Not all e-bike batteries have a battery management system that prevents deep discharge. The capacity of the battery cells is completely extinguished, and a process can be initiated that leads to a short circuit when the cells are recharged.

What should I look out for when buying a battery?


When buying a battery, you have to make sure that proof of the EN 50604-1 standard is provided and that a type certification is available.

Can I build or repair an e-bike battery myself?


All the experts BIKE BILD spoke to strongly advise against it. The cells should only be opened and serviced by qualified personnel.

Can I continue riding with an e-bike battery that has been dropped?


Even a supposedly harmless tipping over of the e-bike can damage the battery and become a source of danger. If in doubt, the energy carrier should be checked for damage at the bicycle workshop.

Are e-bike batteries from brand manufacturers safer than cheap ones?


Hannes Neupert, 1st Chairman of Extra Energy eV, has been dealing with the subject of battery safety for decades and resolutely disagrees: “Any battery can burn. Saying that branded products are definitely safe is like saying that because someone has a lifeguard certification, they can no longer drown.”

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