Adafruit Micro Lipo USB LiIon/LiPoly Charger 100mA 500mA

Tiny USB LiIon/LiPoly charger for single-cell

This compact board charges a single 3.7V or 4.2V lithium-ion or lithium-polymer cell from any USB port. It arrives fully assembled and tested with a 2-pin JST cable included. The default charge rate is 100mA, safe for any compatible cell size and USB source. A solder jumper on the back raises the current to 500mA for larger packs.

Fits directly into a USB port

The PCB-style USB connector plugs into a standard port without extra cables or enclosures. The supplied JST cable mates with common battery packs, leaving the rest of the project free for other circuitry. No external power supply or host controller is required beyond the 5V USB rail. Builders needing multi-cell charging or higher currents will need a different solution.

Three-stage charge cycle with LED status under load

Charging begins with a preconditioning phase, moves to constant current at the selected rate, then holds a constant-voltage trickle to maintain full capacity. A red LED indicates active charging while a green LED signals completion. The 100mA default keeps thermals modest during sustained operation, and the 500mA option remains within typical USB current limits for continuous use.