This circuit uses constant current LEDs to adjust charging current. Leds pass a constant current of about 15mA for an applied voltage range of 2 to 18V. They can be paralleled to give any multiple of 15mA and they light up when current is flowing. The circuit will charge a single cell at 15, 30, or 45mA, or cells in series up to the rated supply voltage limit (about 14V).
