Description of the 12V battery charger electronic scheme :
Below is a very simple circuit that can be used to charge 12v car battery. In this circuit there is installations to control the charging current and voltage. The circuit is based on the circuit MC78T12ABT IC from Freescale. IC is actually a 7812 with a TO-3 package with a capacity of 3A.
T1 is a transformer to reduce voltage and the diodes D1 and D2 perform as a rectifier. C1 capacitor is to filter and the capacitor C2 decoupling. The ground terminal of IC1 is raised to 2.1V using the diodes D3, D4 and D5. Thus, the output of IC1 is fed to 14.1V (12 + 2.1). The battery is charged through diode D6. D6 blocks the flow of reverse current from the battery to the load circuit when AC power is not available. Meter M1 shows the charging current and M2 of the charge voltage.
12 V Car battery charger parts list :
R1 : 2.2K
C1 : 1000uF/25V
C2, C3 : 0.01uF
D1, D2, D6 : BY127
D3, D4, D5 : 1N4001
D7 : Led
IC1 : MC78T12ABT
T1 : 15 V CT
F1 : 1A
