Simple Car Battery Charger Circuit

This is a circuit for battery charger. But the circuit can places in a car. This is a simple design and useful to make it. In this circuit there is facility for monitoring the charging current and voltage. This is the figure of the car battery charger.


The circuit is based on the IC MC78T12ABT. The IC is nothing but a 7812 in TO-3 package with 3A capacity. The transformer T1 steps the mains voltage to 15V AC and diodes D1&D2 does the job of rectification. The transformer T1 can be a 230V primary; 15-0-15V, 3A secondary step down transformer. Capacitor C1 does the filtering and C2 acts as a decoupling capacitor. The ground terminal of IC1 is lifted to 2.1V using the diodes D3, D4 and D5. So the output from the IC1 will be a regulated 14.1V (12+2.1).The battery is charged via diode D6.The D6 blocks reverse flow of current from battery to charging circuit when the mains power is not available.