Another issue of "Useful parts", this time about TWS headphones.

Sometimes you can find cheap chinese True Wireless (TWS) headphones (clones of iPods or Xiaomi Redmi Airdots or anything else) on Aliexpress for around $2 (usually in "bundle deals" section).

If you buy them, you get:

  • a rechargeable LiPo battery of around 100-300 mAh (inside phone case),

  • a charging PCB suitable for low-capacity low-current batteries,

  • 2 tiny batteries from the headphones themselves.

I’ve tried 2 of such headphones. One case battery even came with a protection PCB. Second time it didn’t, so a separate protection module should be added. Interestingly, the built-in protection of one battery had ordinary DW01 and 8205 dual MOSFET, which means its overcurrent protection is set at around 2-3A (typical for such modules), which is probably at higher end for such a small battery.

In both cases the charger seems to be switching, not linear. You can find products that have a display that shows battery charge status in percent, very useful in general, but in particular with batteries inside an RC vehicle that doesn’t have displays. Simpler charger PCBs have 4 LEDs to indicate charge state.

I don’t know what capacity the tiny headphones batteries have. Internets say they typically have 20-50mAh, not sure about these super cheap chinese headphones. They can be used in model projects for sure. Just don’t forget protection PCB.