Why do e-bikes keep bursting into flames?

On Tuesday, an e-bike in east London burst into flames, destroying the first floor of a house and leaving a man in hospital.

The story, sadly, is not an original one – and others have had even more tragic consequences.

But as the popularity of e-bikes shows no sign of slowing down, why are so many of them catching fire?

The answer lies in the battery. More specifically, the quality of it.

E-bikes are generally powered by lithium-ion batteries, the same basic cell as found in laptops, smartphones and electric cars. These products are widespread and generally safe, but not infallible – hence why you can’t put a laptop in your checked luggage, because if it catches fire in the cargo hold, there’s no one around to deal with it.

‘When lithium-ion batteries fail they create a fire unique in its ferocity,’ says Stephen Curtler, product safety manager at Electrical Safety First. ‘When this happens, the battery goes into a process called thermal runaway, which is almost impossible to stop once triggered. 

‘The battery is made up of many individual cells, so when thermal runaway occurs, these cells heat up to an extreme temperature, causing the neighbouring cell to fail and catch fire in what is a domino effect. 

‘This process releases oxygen, meaning a fire of its kind is much more difficult to bring under control.’ 

There is no shortage of shocking footage online of such explosive fires taking place, including those issued by the emergency services. However, while the London Fire Brigade isn’t warning people about exploding phones and laptops, it has issued multiple alerts about e-bikes. This begs the question, why are they so prone to going up in flames?

Consider this – when was the last time you or anyone you knew tried to change the battery on your phone or laptop? Probably never. If you did, you probably took it to a professional.

But when an e-bike needs a new battery, buying a replacement is just a few clicks away, before being shipped and clipped into place. 

However, as with all online purchases, it is a case of buyer beware. The internet is awash with substandard batteries that are not safe for use – often proving so in devastating fashion, leading to damaging, and even fatal, fires in people’s homes.

‘We have major concerns about the safety of e-scooter and e-bike lithium-ion batteries for sale via online marketplaces, where substandard versions of these products as well as chargers are easily sold,’ says Mr Curtler. ‘We urge the government to regulate online marketplaces to stem the flow of dangerous goods entering the market.’

Between January and May this year in the capital alone, the London Fire Brigade had been called to 52 e-bike and 12 e-scooter fires, including a fatal incident on New Year’s Day.

The organisation echoes Mr Curtler’s advice.

‘Cheaper batteries purchased from online sources which don’t necessarily adhere to UK safety regulations are more likely to fail and present an increased fire risk,’ says LFB deputy commissioner Dom Ellis. ‘Our advice is also to buy from a reputable seller.’

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