The US Consumer Product Safety Commission (CPSC) has issued a public warning urging consumers to immediately stop using Unit Pack Power (UPP) e-bike batteries with model numbers U004 and U004-1 due to fire and burn hazards.

While the notice is US-focused, it’s relevant for UK riders because the same UPP models have been discussed in relation to incidents and enforcement activity on this side of the Atlantic. The common thread is that aftermarket batteries are often purchased online across multiple platforms and can lack the safety certification riders assume they’re getting.

What the warning covers

CPSC’s warning names UPP batteries with model numbers U004 and U004-1 and describes reports of overheating and fire. It also urges consumers to use micromobility products that have been designed and certified for compliance by an accredited laboratory to relevant safety standards.

What UK riders should take from this

If you’ve bought a replacement battery online — particularly for a conversion or older e-bike — take five minutes to confirm the brand and model information. If you can’t confidently identify it, treat that as a red flag. For most riders, the safest option remains the dull one: buy the correct, manufacturer-approved battery and charger from reputable sellers, and avoid mismatched chargers even if the plugs “fit”.

Finally, don’t ignore warning signs. Excessive heat, swelling, strange smells, hissing, or smoke are all cues to stop using the battery and get it assessed safely.