With more powerful batteries, ebikes could travel further and carry greater loads, but there’s concern that they could also pose a greater fire risk
by PROF JENNIFER WEN Prof Jennifer Wen is head of the Fire and Explosion Modelling Group and programme lead for Energy and Environment at the University of Surrey’s Institute for Sustainability.
COMMENT
The UK Government recently launched a consultation that seeks public and industry opinion on doubling the legal power output (not speed) of ebikes sold in the UK from 250W to 500W. The plan has sparked concerns within the fire safety community.
There’s a wide range of batteries used on ebikes, but those currently in commercial use are all based on lithium-ion technology. They’re battery packs made of individual battery cells (which can be cylindrical or box-shaped), connected together to provide the required voltage and capacity to power the bike.
While ebikes and escooters offer a great way to get around a city, if the batteries become damaged or fail, they can start incredibly ferocious fires that can quickly spread out of control. And incidents of fires involving lithium-ion batteries are increasing.
According to the London Fire Brigade, lithium-ion battery fires represent the fastest-growing fire risk in the capital. There was a 78 per cent increase in battery fires in 2023 compared to 2022, with 155 ebike fires and 28 escooter fires recorded. A recent Freedom of Information request by The Guardian found that, as of May 2023, fires sparked by faulty ebikes and escooters in the UK had injured at least 190 people and killed eight.
Transport for London, the body responsible for the capital’s buses, trains and taxis, banned escooters from the transport network in December 2021 due to the growing concern over fires.
So how are the fires started? Lithium-ion batteries contain flammable components and reactive materials. Under mechanical impact or through overcharging, these materials react with each other to generate heat, which is accompanied by abnormal electrical behaviour and an increasing reaction rate. This results in cell rupture and the ejection of gases and sparks that can lead to fires and even explosions.
When an ebike battery catches fire, it’s extremely difficult to extinguish because of the underlying electrochemic
