USB li-ion charger

This is a simple li-ion charger without a dedicated li-ion charger IC. This circuit can be used to efficiently and intelligently charge any single cell Li-ion battery pack like mobile battery, digicam battery, etc.


  • Charging via mini-USB connector which is very common.
  • Charging status display by LED
  • Simple circuit by using opamp, resistor, and not by any complex dedicated IC or micro-controller.
  • Charges completely drained (0V) battery packs.
  • Max charging current 500mA(limited by USB supply), depending on battery.

Here’s the corrected schematics and the board design of the circuit.

USB Li-Ion charger circuit diagram


These works are licensed under a Creative Commons License license.

Current Status: Completed and released. PCB and full kit available for buying on request.