What makes an e-bike battery specific

An e-bike battery typically stores 400 to 700 Wh, at 36 V or 48 V, almost always in NMC chemistry for its energy density. It is made of cylindrical cells (often 18650 or 21700 format) welded in series/parallel, with an integrated BMS and, very often, a maker-specific locking system (Bosch, Shimano, Yamaha, Decathlon…). This last point matters: the pack talks to the motor over a proprietary protocol, which complicates DIY repairs.

Recognising an end-of-life battery

The warning signs:

  • Range drop: the assist no longer covers the usual distance, at equivalent route and assist level.
  • Abnormal charging: the battery hits "100%" very quickly then drains abruptly, or refuses to charge.
  • Cut-outs under load: the assist drops on climbs (high internal resistance; the BMS cuts on the voltage sag).
  • Physical signs: a swollen case, smell, abnormal heating — in which case stop using and charging immediately.

Only a cell-by-cell workshop test gives the real SOH. A pack is sometimes condemned by a single failing cell or a locked BMS while most cells stay healthy — hence the value of a diagnosis before any decision.

Repair, replace or repurpose?

Three routes depending on the situation:

  1. Repair: technically possible (replacing weak cells), but often limited by the BMS/motor locking of major brands and by safety requirements. Best left to professionals.
  2. Replacement: a new e-bike battery frequently costs €300 to €700 — enough to sometimes prompt buying a new bike. Always weigh it against the bike's price and condition.
  3. Reuse: if the pack no longer suits the road but its cells retain SOH, they have a place in a stationary storage pack.

Safety and legal obligations

An e-bike battery is never thrown out with household waste: it's illegal and a proven cause of fires in sorting centres. It falls under the WEEE stream and the Corepile take-back scheme. You can return it to a recycling centre, a retailer (take-back obligation), or drop it off at cirBATT for second-life recovery. Never store a swollen or damaged battery near flammable materials.

An e-bike battery's second life at cirBATT

On arrival, the pack is disassembled and each cell tested. Cells above 70% SOH are grouped by performance and reassembled, with our proprietary BMS, into a stationary storage module. An e-bike battery "dead" for the road can thus power a household's solar self-consumption or an SME's peak shaving for years — and you are paid according to the recovered capacity.