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Hidden Battery Fire Risk in the Private Rental Sector

Following a spate of fires in rental properties a home insurance expert is warning people of the hidden fire threat of lithium-ion batteries.

This comes as a new survey by NFU Mutual reveals eight in 10 people are charging, storing or repairing their devices in a way which greatly increases fire risk. 

Lithium-ion batteries are found in almost every household in the United Kingdom, in common items such as mobile phones, e-cigarettes and cordless power tools. Larger types of lithium-ion batteries are found in e-scooters, bikes and electric vehicles. 


These batteries are capable of catastrophic failure, entering a self-heating cycle – or thermal runaway – that generally results in a fire which spreads as the battery expels its material. These fires burn hotter, for longer and are more ferocious than other types of fire. 

To understand the risk faced by UK households, home insurer NFU Mutual commissioned Yonder to conduct a poll of over 1,000 people across the UK. Certain actions can cause devices to overheat or batteries to degrade, increasing the likelihood of fire, and the survey asked whether respondents had done any of these.

The survey found that 80% of people had done at least one thing to leave their device at higher risk of fire. Well over half (57%) had left a device charging overnight and 35% when they were out, with 30% charging devices on soft furnishings like sofas or bedspreads. 

One quarter (23%) had bought a third-party charger online and 13% had used a damaged or frayed charger, while 6% had replaced a battery with a part not recommended by the manufacturer. 

One fifth (20%) had left rechargeable batteries in devices like power tools and 13% had left batteries in direct sunlight – with 8% charging devices in direct sunlight. 

Almost 1 in 10 (9%) had charged large items like e-bikes or e-scooters in hallways or next to doors, essentially blocking their path if the device were to catch fire. 

Luke Barnett, a home insurance expert at NFU Mutual, says:  “While it’s thankfully quite rare for batteries to fail, and are generally safe when used correctly, the results when they do unexpectedly start a fire can be devastating. As insurers, we see several factors that increase the risk of a battery fire and, shockingly, our survey suggests the vast majority of people are not charging or maintaining their devices in the safest way. 

“It may seem over-cautious, but leaving a device on charge overnight or when you’re out, or using a third-party charger, can cause your device to overheat and catch fire. This risk only increases if you’re keeping the device on soft furnishings or in direct sunlight. 

“Power tools and other products where the battery isn’t integral to the product are an often-overlooked fire risk. These items are infrequently used, allowing batteries to age and degrade, and may be stored in excessive heat or other unsuitable conditions, but can easily catch fire, with devastating consequences. 

“And while people may be tempted to save money by purchasing an unofficial third-party charger or replacement battery, this can greatly increase fire risk and ultimately lead to a much bigger bill – not to mention threatening your safety. 

“With recent stories of devastating fires and tragic deaths in fires sparked by overheating batteries, we’re imploring everyone to take fire safety seriously when it comes to electrical devices. As our survey shows, most people have been guilty of being complacent of the risk posed by electrical items, but we’ve had several claims which demonstrate that it can happen to anyone.” 

NFU Mutual has received property damage claims stemming from exploding e-bike, golf trolley and mobility scooter batteries, to mobile phones overheating and starting a fire.  In one claim, a beard trimmer was charging in a bedroom and overheated, sparking a blaze which caused fire damage in half the property. In another, a battery was left in a drill and caused a small fire in a customer’s shed. 

And demonstrating the dangers of third-party replacement, one claim involved a fire caused by a vacuum cleaner exploding as it charged, the owner having just changed the old battery for a third-party replacement. 


NFU Mutual's tips for preventing battery fires

- Avoid unapproved repairs using counterfeit parts 

- Charge devices using approved chargers designed for the product/battery being used 

- Only use batteries designed to be used with the device 

- Safely dispose of old batteries or rechargeable devices 

- Keep a close eye on items after they have been dropped, suffered a collision or other damage to ensure the battery is not overheating 

- Store electrical items and batteries appropriately – out of direct sunlight, uncovered by things like coats and blankets, and away from flammable material 

- Charge devices away from direct sunlight or extreme heat and avoid charging in areas like under the bed or on the sofa 

- Do not leave batteries plugged into a charger once they are fully charged 

- Remove detachable batteries from devices like power tools when not in use 

- Check for the CE or UKCA safety marking to ensure battery and chargers meet safety standards  

-Ensure areas where you are charging batteries have working smoke or heat detectors nearby. 

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