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Hacker News front pageJulia Evans4 min readintro

Replacing the old battery on rechargeable bike lights

Read on jvns.caHN 207·125 commentsLobsters 24

Summary

Julia Evans documents how she opened a decade‑old rechargeable bike light, identified the dead Li‑ion cell, sourced a replacement on AliExpress, desoldered the old pack and soldered in the new one, then glued the housing back together. The light works again after a $20 CAD fix.

  • Identify obscure battery markings (e.g., "LIR2477") by visual match or simple web search; LLMs can help but aren't required.
  • Desoldering a small Li‑ion pack can be done with a pump and patience, avoiding overheating the cell.
  • Cheap replacement cells (≈$3) are often available on marketplaces like AliExpress when OEM parts are discontinued.
  • Re‑assembly can be improvised with silicone glue and a few remaining screws; perfect sealing isn’t always necessary for functional repair.

Engineers who tinker with legacy hardware can extend device life cheaply by learning basic desoldering and parts‑identification techniques.

4/10
electronicsrepairhobbymakerspacebattery

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