This 12V battery charger circuit is a high-performance charger for gelled-electrolyte lead-acid batteries. This charger quickly recharges the battery and shuts off at full charge. Initially, charging current is limited to 2A. As the battery voltage rises, current to the battery decreases, and when the current has decreased to 150mA, the charger switches to a lower float voltage, which prevents overcharge. When the start switch is pushed the output of the charger goes to 14.5V.


As the battery approaches full charge, the charging current decreases and the output voltage is reduced from 14.5V to aout 12.5V, terminating the charging. Transistor Q1 then lights the LED as a visual indication of full charge.

12 Volts battery charger circuit diagram

12v battery charger