Cordless tools, electric bikes and other devices powered by lithium-ion batteries have become part of everyday life in many homes – but as their popularity has grown, so has the number of fires caused by their batteries. While the damage is limited in minor incidents to, for example, the destruction of the tool or scooter in question, in the worst-case scenario an entire building has been destroyed.

“Where lithium-ion batteries are concerned, the risk of fire usually stems from the battery being damaged or overheating, or when a fault emerges during charging,” explained Kristel Kobi, Head of Property Damage at Seesam. “You should be particularly cautious with batteries and chargers bought from Chinese discount retailers, as there might be no way of verifying their quality or how safe they are. The risk increases when people start modifying batteries themselves or using them for things they weren’t intended for. It pays to bear in mind that a lithium-ion battery fire isn’t a normal fire, but a chemical chain reaction that’s gotten out of control, develops rapidly and is incredibly difficult to stop using anything you might have at home. And even if you do manage to put it out, the chemical reaction inside the battery can continue, meaning it could catch fire again.”

Although battery-related fires are mostly associated with electric vehicles, battery-powered tools also pose a significant risk.

A strimmer battery left charging destroyed a building

The most serious battery-related incident for Seesam occurred after an ordinary day’s gardening: little more than an hour after a homeowner used a strimmer and put its batteries in the garage to charge, family members noticed smoke coming from the building. Within minutes, the entire garage was ablaze, destroying it and all of its contents.

The insurance payout amounted to nearly 165,000 euros, but since some of the property in the garage – including a car – was not insured, the actual loss was even greater.

Due to the extent of the damage, it was impossible to determine why the batteries caught fire.

“That’s quite common in cases like this,” Kobi noted. “Fires often obliterate much of the evidence you’d otherwise find, making it impossible to determine the exact cause. A lot of fires involving lithium-ion batteries start when devices are charging, or immediately afterwards, but the cause can just as easily be mechanical damage to the battery, a manufacturing defect or incorrect use.”

Smaller battery-related fires occur more frequently. For example, in one incident covered by Seesam in which an electric bike battery caught fire, the insurance payout came to nearly 7700 euros despite the fact that the fire was extinguished before it could turn into a major blaze. In another case, a power bank with a faulty cable catching fire resulted in extensive smoke damage to the entire home and to much of its household property. The loss in this case amounted to nearly 30,000 euros.

The greatest risks arise while charging

Kobi says that a significant proportion of accidents could be prevented by adopting appropriate charging habits – the rule of thumb being that you shouldn’t leave batteries charging unattended or use batteries or chargers of unknown origin.

“Although it can be impossible to determine after a fire whether a battery was genuine or not, the sheer number of cheap, uncertified batteries and chargers on the market has increased the risk of accidents,” she warned. “The lower price might save you 30 or 40 euros initially, but in the worst-case scenario it could cost you your entire home.”

Lithium-ion batteries are highly sensitive to extreme operating conditions, which is why manufacturers build protective systems into both the batteries and the chargers. However, these do not rule out all risks. As such, Kobi recommends always using the chargers and batteries specified by the manufacturer, only doing so when you’re at home, and to stop using any battery immediately if it’s taken a heavy knock, has swollen in size or is hotter than usual.

If a high-capacity lithium-ion battery (such as the one in an electric scooter) catches fire, Kobi advises against attempting to extinguish it yourself. “Those sorts of batteries catching fire can cause an explosion, hurling red-hot pieces of metal in all directions and releasing toxic gases,” she cautioned. “The smartest thing to do is to leave the room, closing the door behind you, and call the emergency services immediately.”

Recommendations for the safe use of batteries

Never leave charging batteries unattended.
Once the battery is fully charged, remove it from the charger, then unplug the charger from the mains.
Use the manufacturer’s own chargers and batteries.
Never charge a battery on a bed, sofa or any other flammable surface.
Keep your devices and spare batteries in a cool place.
Never use batteries that are swollen or cracked or that have taken a heavy knock.
If a battery catches fire, leave the room, close the door behind you and call 112.