HomePractical recommendationFire, burning, intense heat: These risks are inherent in lithium batteries

Fire, burning, intense heat: These risks are inherent in lithium batteries

Lithium-ion batteries can be found everywhere: in smartphones, tools, cars and whenever there is a need for energy independent of the mains supply. They offer a whole range of advantages, such as high efficiency and long service life. They are also relatively inexpensive and can withstand many charging cycles. Nevertheless, the Li-Ion batteries are repeatedly criticised. One reason: Overheated batteries were responsible for fires in the past. We explain how the so-called thermal runaway occurs, whether it can be prevented and how to store lithium-ion batteries safely.


What is a thermal runaway?

Thermal runaway” or “thermal cycling” refers to a process that leads to the burning or exploding of a lithium-ion battery. If a battery overheats, a battery cell may start to burn. A chain reaction occurs: The burning cell heats up the neighbouring cell, which is also burning. It’s referred to as explosive burning.


Why does a battery overheat?

Usually the cause of a thermal runaway is found inside the battery. Construction defects, dust particles or damage can lead to a short circuit. Normally the positive and negative pole are separated from each other. This is ensured by the separator, a thin plastic film. If cracks appear in the separator, a short circuit and subsequent heat generation may occur. Especially fatal: Small damages usually do not yet cause a fire, but they are getting bigger and bigger. If a battery is damaged, the fire often breaks out several hours later. If an e-car is involved in an accident, its battery may still ignite after 72 hours or much later. You must definitely wait for this period of time, to be on the safe side. This also applies to other types of damage, such as when a smartphone has fallen to the floor.


Are you saying that lithium-ion batteries are dangerous?

Overheated lithium-ion batteries can cause fires in electric cars, smartphones, navigation systems, laptops and many other electrical devices. However, you can reduce the risk by following some important safety instructions:

  • Do not use fast charging.
  • Do not place battery-operated devices in the sun.
  • Only use original charging cables.


How do I recognise a defective battery?

You cannot normally see from the outside whether a lithium-ion battery has been damaged. An odour of plastic or gas can be an indication, and the bloating of the device also indicates a defective battery. Another security tip: A battery should never be warm when switched off.


How do I react in the event of fire?

If there really is a fire: Lithium-ion batteries can be erased with water. However do not make any risky attempts to extinguish the fire, it is better to call the fire brigade on 112.


More information and suitable products for the safe storage of lithium batteries can be found here (in German only).

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