E-Bike Conversion Kits and Aftermarket Batteries: Where the Fire Risk Comes From

A conversion kit can turn a pushbike into an e-bike for a fraction of the price of a new one. It can also bring together a battery, a charger and a motor from three different sellers, fitted at home, for the first time.

Why fire services single them out

London Fire Brigade says it has particular concern about the risk posed by conversion kits and modified e-bikes. Not every kit comes with a battery or charger, so these are often bought separately, sometimes from different sellers, which raises the chance of an incompatible charger. DIY installation can also damage the kit (London Fire Brigade, n.d.).

Its warnings are blunt: an incompatible or substandard charger risks overcharging the battery (London Fire Brigade, 2024), and there are currently no safety standards for the conversion kits themselves (London Fire Brigade, 2025).

The Australian picture

NSW's information standard for e-micromobility products requires suppliers to give buyers warnings against modifying the device (NSW Government, 2025). Queensland fire officials have also reported people making home modifications to the battery packs that power their devices, alongside incompatible charging equipment, as causes of fires (South Burnett Online, 2023).

Aftermarket batteries

The same logic applies to replacement packs. A higher-capacity or cheaper battery from a different maker may not match the bike's controller, charger or mounting, and its management system is unknown. Second-hand batteries add the risk of hidden damage.

If you already ride a converted bike

• Have the conversion checked by a professional bike mechanic.
• Use the charger matched to that battery, and never a universal one.
• Don't charge it unattended, overnight, or near the only way out.
• Store the battery in a containment bag when it is off the bike.
• When the battery needs replacing, use one specified for the system.

Our guide to swollen and damaged batteries covers when to take a pack out of service. A 2 m x 2 m e-bike blanket and the full e-bike range round out the kit.

General guidance only. Fire blankets and containment bags contain a fire and buy time; they do not extinguish thermal runaway. In any battery fire, get clear and call Triple Zero (000). Our extinguishers are certified to EN 3-7:2004+A1:2007 and are supplementary to your statutory fire safety equipment.