Lithium-ion battery failures are driving a sharp rise in electric bike fires across the UK, with new data highlighting the growing risk to users.
A growing number of electric bike fires are exposing the risks hidden inside the lithium-ion batteries powering the UK’s e-bike boom, with new figures linking these incidents to 18 deaths and almost 700 injuries since 2019.
More than 2,000 fires involving e-bikes, e-scooters or their batteries were recorded by UK fire and rescue services between 2019 and 2025, according to data obtained by BBC Verify. The figures point to a particularly rapid increase in battery-related incidents, which climbed from just 32 in 2019 to 605 last year.
The rise comes as e-bikes become increasingly common on British roads. An average of 153,000 new electric bikes have entered use each year since 2020, according to the Bicycle Association, meaning a larger battery population is also creating more opportunities for faults, damage and unsafe charging practices to result in fires.
Why lithium-ion batteries can catch fire
The danger is rooted in the chemistry inside the battery.
E-bikes typically use lithium-ion battery packs containing multiple individual cells. During normal operation, lithium ions move between two electrodes while an electrolyte allows the battery to store and release energy.
Problems arise when a cell is damaged, overheated, manufactured incorrectly or subjected to electrical conditions outside its intended limits. A short circuit inside the cell can generate heat, which can trigger a chain reaction known as thermal runaway.
As the temperature rises, the battery’s internal materials can begin to break down and release flammable gases. Those gases can ignite, generating still more heat and potentially causing neighbouring cells to fail. The result can be a rapidly escalating fire that is difficult to control.
The UK Government specifically identifies thermal runaway as a serious fire risk associated with lithium-ion batteries used in e-bikes.
This also helps explain why these incidents can become dangerous so quickly. A battery may contain a substantial amount of stored chemical energy in a compact package, while a failure can involve several cells rather than a single conventional ignition point.
What makes electric bike fires more likely?
Battery quality is one part of the equation, but it is not the only risk.
Government guidance identifies counterfeit or poorly manufactured products, physical damage, incompatible chargers and unauthorised modifications as factors that can increase the likelihood of an e-bike fire.
Altering a bike’s electrical system can change the loads placed on its battery and components, potentially generating excessive heat.
Charging is particularly important because it combines the battery’s stored energy with an external electrical supply. Using the wrong charger can create unsafe charging conditions, while damaged batteries may fail even when apparently being used normally.
A battery that becomes unusually hot, swells, leaks, produces a strong chemical smell or makes hissing or cracking noises should therefore be treated as a potential failure rather than a minor fault.
How can the risk of electric bike fires be reduced?
The most effective measures are relatively straightforward. Owners should use the charger supplied or approved by the manufacturer, avoid modifying battery systems and buy batteries and e-bikes from reputable sellers.
Charging should take place somewhere that does not obstruct an escape route, and batteries should not be left charging while people are asleep or away from home. Government guidance also advises against covering a battery or charger while it is operating.
Physical damage deserves particular attention. Batteries can be compromised during crashes or after being dropped, even when damage is not immediately obvious. A suspected damaged battery should not be charged or used.
Most importantly, prevention should not be confused with firefighting. If a lithium-ion battery begins smoking or catches fire, official advice is to raise the alarm, leave the building and call 999 rather than attempting to extinguish it.
The rise in electric bike fires does not mean e-bikes are inherently unsafe. Instead, the data highlights a specific vulnerability of high-energy lithium-ion systems: when a battery fails, the consequences can escalate rapidly.
As the UK’s e-bike fleet continues to expand, understanding how batteries fail may be just as important as encouraging people to use them.
