[Earphone Repair] I tried replacing the battery in a rare cuff-style earphone myself [LiPo 400909]
Today, I’d like to share the story of repairing a rather uniquely shaped cuff-style earphone. Since most commercially available wireless earphones never fit my ears properly, this unusual design has been an absolute lifesaver for me.
However, recently, only the right earphone started giving a low battery warning just about 30 seconds after turning it on… Since I hadn’t changed how I used or charged it, it seems the battery’s lifespan had finally come to an end.
Disassembly Revealed a LiPo Battery
After carefully taking the earphone apart, I confirmed that a small lithium-polymer (LiPo) battery was housed inside.
The label stamped on it read “400909“. While this size is a bit uncommon, searching on AliExpress showed they were being sold for less than 500 yen each.
Replacing the Battery Myself! The Key Watch-Out Is “Heat"
Once the ordered battery arrived, I immediately started the replacement process.
The battery is of the type that is soldered directly to the circuit board. LiPo batteries are sensitive to heat, and excessive heating carries the risk of expansion or fire, so I proceeded with the soldering work carefully while keeping a close eye on temperature management.
Replacement Successful! The 30-Second Warning Is Gone
After the replacement, I reassembled everything as it was and turned the power on…
That pesky low battery warning that used to pop up after 30 seconds completely disappeared!
The battery life for both the left and right sides returned to roughly the same level, and I can now use them comfortably just like before. The battery replacement worked like a charm.
Was the Old Battery Slightly Swollen?
Looking at the removed battery again, the surface felt somewhat plump, or at least it seemed that way… While it wasn’t a case of severe swelling, there is no doubt it had degraded from long-term use.
Conclusion: Keeping Your Favorite Earphones Alive Longer
These cuff-style earphones are hard to replace with other off-the-shelf products. Buying a new pair might have been impossible to find, but I successfully extended their life by replacing the battery.
If you are also struggling with degraded earphone batteries, checking the size and structure of the battery might just mean you can repair it yourself much more easily than you think.
That concludes my account of repairing a uniquely shaped pair of earphones on my own this time around.