Electric bicycles and electric scooters, or e-bikes and e-scooters, are more popular than ever, providing riders with a lower-cost and environmentally friendly way of getting around. But, unknown to many users, the lithium-ion batteries that power e-bikes and e-scooters have also been known to catch fire and cause explosions. With such batteries also present in a growing number of household devices, their use within communal buildings represents an increasing safety risk.
Growing uptake of electric bikes presents fire risk
In the UK, the market for e-bikes and e-scooters has undergone significant growth in recent years. According to data from market intelligence agency Mintel, sales of e-bikes almost tripled over the past five years to 155,000 in 2022.
The power supply to the majority of e-bikes and e-scooters are provided by a lithium-ion battery which can be charged in the home. Unlike conventional lead-acid batteries, lithium-ion battery cells combine a flammable electrolyte with significant stored energy, allowing them to provide higher energy densities and extended lifetimes. Although more expensive than their lead-acid equivalents, lithium-ion batteries are significantly lighter, making them ideally suited for use within electric vehicles.
Lithium-ion batteries are typically safe to use when operated in accordance with manufacturer specifications. However, the hazards increase where normal operating conditions are deviated from. If the lithium-ion battery cell creates more heat than it can effectively disperse, it can lead to a rapid uncontrolled release of heat energy, known as ‘thermal runaway’. In the worst-case scenario, this can result in a fire or explosion. When fires do occur, they tend to escalate very quickly, produce highly toxic gases and can make fire control and suppression extremely challenging, increasing the importance of fire prevention and evacuation strategies.
Lithium-ion batteries are also increasingly used in a wide range of household appliances, including many of today’s mobile phones and laptops. All lithium-ion batteries carry a fire risk, but that risk is greater with e-bikes and e-scooters. Partly, this is due to scale: the larger the battery, the greater the size of any potential explosion. But there are other reasons. Physical damage, such as impacts from a crash, could cause the battery to malfunction. Unlike most phones and laptops, many e-bikes also have removeable batteries for easy charging, which users may then replace with cheap, faulty, or untested alternatives.
Why do lithium-ion batteries catch fire?
The risk of lithium-ion battery fires has been on the rise in recent years, a fact that reflects their growing adoption among members of the public. According to the London Fire Brigade, lithium-ion battery fires represent the fastest growing fire risk in the capital. In 2022, the service attended 87 e-bike and 29 e-scooter fires, a total of 116 fires. So far in 2023, it reports being called to an e-bike or e-scooter fire, on average, once every two days.
Specific causes of lithium-ion battery fires include, but are not limited to:
User error where devices are charged with incorrect charger with the wrong output
Charging the device or device battery after it is fully charged
Charging of multiple device batteries at any one time, overloading the circuit
Improper storage of lithium-ion batteries, such as in direct sunlight, inside hot vehicles, or in proximity to flammable liquids
Fires following maintenance and repair by unqualified agents
Where speed restrictions on imported vehicles have been removed, fires may result from overheating
Users not allowing the battery to cool before attempting to re-charge or charge another device or vehicle
Use of cheap or unregulated batteries, such as those purchased during self-performed bicycle conversions and motor installations
Manufacturing defect in the supplied battery
External damage to the battery
Lithium-ion battery fires are typically the result of accidents. One common cause of such fires is the use of widely available phone chargers to charge an electronic cigarette or vape. Although users may simply be reaching for the nearest available charger capable of serving the device, they may not consider that the different power requirements mean that they are overloading the battery.
Similarly, the use of single-use vapes has causes house fires in the UK to soar by 108% in the last two years, according to data from insurer Zurich. The same research reveals that almost three out of four vape users are unaware that these devices contain lithium-ion batteries.
Any appliance that utilises a lithium-ion battery has the potential to initiate a fire. This includes hoverboards, massage guns, power tools, vacuum cleaners, and other appliances.
Lithium-ion fires in communal buildings – mitigating against risk
Owing to the large numbers of people present within communal office and residential buildings, the risk of lithium-ion battery fires within such premises is particularly severe. Where bikes are stored in communal areas or escape routes, a fire breaking out can quickly block people’s ability to escape.
To mitigate against the likelihood of a lithium-ion battery fire, owners and building managers should adopt the following measures:
Educate building users as to the dangers of lithium-ion battery fires
Make building users aware of the common warning signs of lithium-ion battery failure, including heat, bulging, noise, smell, performance, and smoke
Encourage users to physically inspect charging cables and equipment for damage or compromise before and after charging
Encourage users to allow batteries to cool before attempting to re-charge
Encourage building users to dispose of lithium-ion batteries via the appropriate local recycling locations; disposal of lithium-ion batteries in regular rubbish or recycling should be prohibited
Where lithium-ion batteries are permitted, provide designated charging areas for e-bikes and e-scooters; ideally, these should be located as far as possible from buildings, structures, and utilities, including waste compounds, gas storage, and other combustible storage areas
Ensure that charging areas do not obstruct fire exits
Only use charging equipment supplied by the manufacturer of the relevant machine, or where OEM-approved compatible replacement batteries have been fitted by a competent person; do not permit the use of voltage converters
Do not permit batteries to be charged unattended
Ensure charging facilities are adequate for user demand; do not permit the use of multi-point adapters for the charging of lithium-ion batteries
Where lithium-ion battery vehicles are owned or supplied by building owners, ensure all vehicles are included within a documented
Portable Appliance Testing Programme
Charging points should be protected against mechanical damage by vehicles, such as being installed above ground level, or protected by kerbs, bollards, or metal barriers
Implement procedures for the reporting of faults or damage to batteries and/or charging equipment
However, not all lithium-ion battery fires originate from within the affected premises. In multiple cases with which Lockton is familiar, fires have spread to a building from a neighbouring site.
As such, although the above measures remain effective at preventing fires from within the premises, the security of a building and its residents cannot be guaranteed without wider engagement with neighbours, recognising the mutual threat posed by inadequate lithium-ion battery handling.
This article has been included in the Lockton Risk Radar: Specialist Insurance Publication – October 2023 Edition (opens a new window).
For further information, please visit the Lockton Risk Control page (opens a new window), or contact:
Mark Hallworth, Risk Management Executive – Property Team Lead