This simple circuit for charging car batteries is interesting for its behavior which can be defined as similar to that of the alternator regulator mounted on cars.

It is in fact able to charge the battery up to the chosen voltage (normally 13.8 V) and keep it constantly without the risk of overcharging.

Its power is not bound to the scheme, which refers to the most convenient and recommended solution, but also works in smaller dimensions, taking longer, or larger with better results.

Bill of Materials

R1: 4,7 ohm

R2 : 100 ohm

R3 :1 K ohm

R4 : 1,5 K ohm

R5 : 680 ohm

P: 1 K ohm potentiometer

C1 : 1000 uF 25 V

C2 : 2,2 mF 25 V

T: Transformer 80 VA - 13,5 V

D1 : Bridge rectifier

D2-D3 : 1N4001

D4 : diode 50 V 15A

SCR :100 V 8-10A

IC : 7912 voltage regulator

LED :

F1- F2 : fuse

Gerber files available