Li-ion batteries – a fire hazard

Physical damage to battery cells, pollution in the electrolyte or the poor quality of the separator may cause a fire in li-ion batteries.

An explosive fire in a Lithium-Ion battery

In June 2018, a client of ours experienced an explosive fire in a Lithium-Ion battery used for a custom-built electric bike. The owner of the bike was about to show the battery to his family when it suddenly caught fire lying on the kitchen table! The battery was not connected, neither to the charger nor to the bike.

The fierce fire, experienced by our client as being like fireworks, could not be extinguished, and the fire spread to the interior and the building structure, causing a near total loss of the building.

Our own investigators have done technical studies of the damaged battery and the battery cells. The probable root cause of the fire is physical damage to the battery, causing thermal runaway in the battery. The built-up pressure was released through cracks in the first battery cell affected, causing thermal runaway in some of the other cells.

Root cause of the fire    

Senior researcher Helge Weydal, at the Norwegian Defence Research Establishment (FFI), explained the hazards of Li-Ion batteries in an article in Risk Consulting issue 2/2017. Fires can be caused by physical damage to battery cells, such as that which our client experienced, or they might also be caused by pollution in the electrolyte or the poor quality of the separator.

li-ion battery cells
Investigators from If checking li-ion battery cells that started the fire

Countless numbers of devices

The number of devices using Li-Ion batteries in households and businesses worldwide is enormous. We are surrounded by billions of devices: mobile phones, laptops, radios, cameras, flashlights, radios. Equipment that consumes even more energy, such as lawn mowers, other power tools, and in the Nordic countries even rotary snowploughs, belong to households.

Electric cars are coming rapidly into several international markets. Buses, ships, ferries, large trucks, and even aeroplanes are being developed for commercial purposes, all using Li-Ion technology as the power source. Large Li-Ion battery banks are used in power storage for optimising solar power technology.

We are surrounded by billions of devices.

Fire statistics trends

Is there an increased risk of fire in introducing all these devices into our homes and workplaces? Our statistics do not show any clear trends, considering the enormous number of units. We receive fire claims caused by batteries in or charging for flashlights, electric bikes, drones, radios, and even children’s toys. But still the ‘normal’ root causes, such as electrical faults, not following safety manuals, oil fires, and hot work, are much more common sources of fire.

Looking across the Atlantic to the US, interesting stories unfold. During the past few years, up until 2017, more than 500.000 hoverboards were recalled after at least 99 reported events of smoking, fire, or explosions in devices, according to the Consumer Product Safety Commission. After introducing strict guidelines for approving batteries for hoverboards, the problem seems to have nearly disappeared in that market.


The US Navy banned the use of e-cigarettes after 15 incidents in less than a year caused injury to personnel or material damage. The statistics by the Federal Aviation Administration (FAA) build up for this concern. Looking all the way back to 1991, the authorities have registered all events of overheating, smoking, or fire in Li-Ion batteries in passenger and cargo aeroplanes or registered at airports.

The curve grows steeper every year with the increasing number of devices in our society. There were 238 reported incidents over the whole period, of which 94 occurred just in 2017–2018. Of these 52% occurred either in battery packs or e-cigarettes, and 18 % started in mobile phones.

The list of recalls over the years is long. A quick Internet search shows HP and Dell laptops have experienced recalls, as well as the Samsung Galaxy Note 7 and even battery-powered radios.

Reported recalls by device

Reported recalls by device

Electric cars

Electric cars are seldom the centre of attention related to battery fires, but there have been some examples of wrecked cars with heavy damage to the battery pack causing thermal runaway and fire. Not only can the batteries form a fire risk. In the case of electric cars, even though they have several built-in safety barriers in their battery and charging systems, the use of so-called emergency chargers in regular sockets can lead to overvoltage and fire in electrical switchboards or in sockets.

If Insurance investigators in Finland decided to examine whether driving nails through the battery pack of an electric fat scooter would cause a fire.

Remember the power needed to charge such large batteries might often create much larger resistance in the circuits than they were originally built for. Correctly dimensioned over-voltage protection must be fitted, alongside the use of fuses that are adequate for such charging.

High-energy fire

Taking a step back, given all the devices on the market, the number of fire incidents is not very high. The problem is the fierce fire experienced, just as in our client case mentioned above. A Li-Ion fire is difficult to fight due to the chemical reaction continuously creating oxygen.

Mitigating fire risk

There are several mitigating actions taken by battery suppliers to prevent fire from occurring. As Helge Weydal Larsen explains, there would normally be built-in surveillance of charging and battery status. An X-ray of all batteries, to ensure the electrolytes are not polluted, is a precaution used by serious battery producers. Power tools are often considerably better protected from external impact and damage than regular consumer goods.

Why is all this important information for industrial businesses?

During our client visits, we often come across private devices such as radios brought to the workplace, power banks, and e-cigarettes.

A common recommendation issued in loss prevention reports is that the employer must keep track of these devices. Private electric and chargeable devices should be inspected and approved before allowing employees to bring them to work, regardless of the power source.

Means of getting around

In the larger industrial estates and warehouses, we can often find employees using kick-scooters to cover large distances rather than walking on foot. Introducing electric kick-scooters or fat scooters might be even more tempting. However, be aware that this might introduce a new fire hazard to the company. Tests done by our investigators clearly show that physical damage to battery packs might start a thermal runaway in the battery and consequently a fire. Rough handling of scooters at the workplace can therefore, in a worst-case scenario, cause injury to personnel or a fierce fire.

With the introduction of large battery banks storing power from PV panels for later use, a new fire risk can occur. These banks should be stored in separate fire compartments and protected with proper extinguishing systems, or preferably located an adequate distance from the production buildings. This could be the difference between an isolated battery fire and total damage of the location.

Better battery safety

Make sure the batteries used in your business are of high quality and approved according to relevant standards.

  • Inform all employees of the possible fire hazard. This is also good employee policy, caring for their safety.
  • Do not allow employees to bring personal Li-Ion devices to the workplace without approval.
  • Ensure charging is done in a safe manner, and ensure that electrical systems are properly dimensioned.
  • We recommend that charging is only done on a non-combustible base, away from any storage, and in areas with properly fitted smoke detection.
  • Make sure that devices exposed to rough handling and damage are inspected. Greater than usual heating of the device when charging or during use is a sign that something is wrong.
  • Make sure connections are properly fitted and undamaged, to prevent electric arcs.
  • Follow airline regulations for transporting and handling battery-powered devices when travelling.

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Photo of Anders Rørvik Ellingbø.

Anders Rørvik Ellingbø

Head of Risk Management Services, Norway

Contact Anders Rørvik Ellingbø