Can LiPo batteries explode 1

When lithium-ion batteries explode How does a battery fire start?

A man wants to charge his e-bike battery. Then the battery catches fire and the whole house burns down - as happened a few days ago in Gimbsheim near Worms. How does a battery fire come about and how can you protect yourself?

How does a battery fire come about?

Lithium-ion batteries have a high energy density, which is why they are so suitable for powerful devices such as e-bikes, notebooks or self-propelled lawnmowers. The high energy density has a downside, however, and that is the statistically low, but still existing risk of fire and explosion if things get out of control in the battery, there is a short circuit and the large amount of energy is discharged in one fell swoop, so to speak.

What is happening there?

The following happens: Like any normal battery, an accumulator has two chambers - electrode spaces - one on the anode and one on the cathode side. The charge carriers - in this case the lithium ions - flow between these two chambers in one or the other direction, depending on whether the battery is being used or is being recharged. So that everything happens in a controlled manner, there is a semi-permeable partition between the chambers, the so-called separator.

Semi-permeable means that the charge carriers in the battery - i.e. the lithium ions - can already penetrate the separator, but only slowly and carefully.

If the separator is damaged - be it due to excessive heat, be it because it fell on a hard floor or simply due to a production error, this partition becomes more permeable to the lithium ions than it should be - and that means in plain language: There is a short circuit. This means that the lithium ions migrate very quickly through the battery and chemical reactions occur very quickly, in which a great deal of energy is released in a short time. This leads to a chain reaction: the hotter the battery, the more damaged the separator and the faster the reactions run, so that temperatures of over a thousand degrees can arise.

How big is the risk?

It has to be said: the overall risk of a battery catching fire is low, less than one in a million. But because there are now millions of lithium-ion batteries, it just happens again and again.

How can you avoid battery fires?

There are a few precautionary measures that can be taken to reduce the risk. This includes always charging batteries with the devices that are designed for this. At temperatures between 10 and 30 degrees Celsius, if it is too cold or too warm, the risk of short circuits increases. If lithium-ion batteries are not going to be used for a longer period of time - e.g. on an e-bike during the winter break - remove the battery from the device, store it in a reasonably cool place, preferably when it is half full.

If the battery is too empty, there is a risk of deep discharge during prolonged storage - this also increases the risk of fire when recharging. If the battery is taken from a cold garage, it is best to let it warm up again at room temperature. And when recharging for the first time, it is advisable to stay close and check every now and then whether everything is okay.

How do you extinguish a battery fire?

However, once the battery catches fire, the rule is: Do not try to extinguish it with water. Because that can only trigger the actual explosion. Because of the great heat, water molecules can split into hydrogen and oxygen. And free hydrogen is extremely dangerous, then it comes to an oxyhydrogen reaction. Extinguishing powder is more suitable, which is also contained in good fire extinguishers. And the best thing is to call the fire brigade right away.

SWR knowledge. By Gabor Paal. Online: G. Paal and R. K├Âlbel

As of October 18, 2018, 1:24 p.m.