Everything for Electronics
Posted in: Nuts and Volts (December 2012)

USB Li-ion Charger

    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.



[Source] http://circuitsdiy.com