Reviving Ancient Rechargeable Bike Lights

By Julia Evans (Rewritten)

I recently rediscovered a pair of rechargeable bike lights I purchased a decade ago. After leaving them unused for years, I attempted to charge them, but the results were disappointing: they lasted roughly 5 minutes before dying again.

Despite having limited knowledge of electronics, I've long been interested in the possibility of repairing old gadgets. This felt like the ideal entry-level project since the culprit was likely just a degraded battery. To tackle this, I headed to my local queer makerspace to access a soldering iron and a supportive community.

Disclaimer: I am not an electronics expert. Consequently, this guide contains no professional safety warnings because I simply don't know enough about safety to provide them.

The Repair Workflow

Step 1: Breaking In

The exterior of the light was made of silicone. I performed a somewhat haphazard cut along what looked like a seam. While I definitely ripped some of the material and the process was messy, I successfully reached the internal circuit board.

Step 2: Disassembly

I located the screws holding the internals together. To minimize the risk of losing tiny parts or failing to put them back, I removed only the absolute minimum number of screws required to free the board.

Step 3: PCB Extraction

Once the screws were out, I pulled the circuit board from the housing.

Looking at the board, the battery connection is located roughly to the left of RI3 and above Q2.

Step 4: The Desoldering Process

Since I had never desoldered before, I consulted an iFixit guide. Following that advice and some local tips, I used this strategy:

1. Use a desoldering pump to clear the bulk of the solder.
2. Gently pull the components apart to separate them.
3. Crucial: Take frequent breaks to let the battery cool down to avoid overheating.

Initially, I thought I had to remove a specific metal piece, but it turns out the replacement battery comes with its own tab, so I could leave that part alone.

Step 5: Identifying the Component

The battery markings were cryptic, reading something like 3 and LI???77. There was a metal piece welded to the top that seemed impossible (and dangerous) to remove.

I generally try to avoid LLMs, but I was completely stuck on the part number. I asked one, and it suggested the model LIR2477. A quick search confirmed this matched my battery perfectly. (I am still curious about non-LLM methods for identifying such parts!)

Note: A friend, Lauria, showed me how to use the DigiKey search tool, which is a great resource, though they didn't stock this specific part.

Step 6: Procurement

I sourced the following from AliExpress:

order_details:
  vendor: AliExpress
  shipping_time: 2 weeks
  currency: CAD
  items:
    - part: LIR2477
      count: 2
    - part: silicone_adhesive
      count: 1

Step 7: Final Assembly

Once the parts arrived, I returned to the makerspace to finish the job.

• Solder the new batteries into place.
• Reinstall screws (though I dropped a few that were too small to find).
• Apply silicone glue to the casing.
• Perform a "halfhearted" attempt at clamping the pieces.
• Let the glue cure for 24 hours.
• Dispose of old batteries at a proper recycling center.

Conclusion

The final result isn't perfectly seamless, but it's functional. I'm currently in a tragic predicament where I have to wait for a new Mini USB cable to arrive because I've discarded all my old ones, so I haven't yet verified the new battery's actual runtime.

The total cost was approximately: $\text{Total} \approx \$20 \text{ CAD}$

Regardless of whether the repair lasts forever, it was a rewarding experience to learn a new skill and fix something with very little prior electronics knowledge!