This auto battery charger uses no transformer, rectifier, or filter capacitors on the schematic. No reason why you cannot add these. This charger will quickly and easily charge most any lead acid battery. The auto battery charger delivers full current until the current drawn by the battery falls to 150 mA. At this time, a lower voltage is applied to finish off and keep from over charging. When the battery is fully charged, the circuit switches off and lights a LED, telling you that the cycle has finished.

Auto Battery Charger Circuit Schematic

Auto Battery Charger Schematic

Auto Battery Charger Circuit Schematic

A heatsink will be needed for this auto battery charger ( U1.)

Auto Battery Charger Parts List

Resistor
R1  500 Ohm 1/4 W
R2 3K 1/4 W
R3 1K 1/4 W
R4 15 Ohm 1/4 W
R5 230 Ohm 1/4 W
R6 15K 1/4 W
R7 0.2 Ohm 10 W
Capacitor
C1 0.1uF 25V Ceramic
C2 1uF 25V Electrolytic
C3 1000pF 25V Ceramic
Diode
D1 1N457
Transistor
Q1 2N2905 PNP
Regulator
U1 LM350
Op Amp
U2 LM301A
S1 Normally Open Push Button Switch
MISC Wire, Board, Heatsink For U1, Case, Binding Posts or Alligator Clips For Output

To use the auto battery charger circuit, hook it up to a power supply/plug it in. Then, connect the battery to be charged to the output terminals. All you have to do now is push S1 (the “Start” switch), and wait for the circuit to finish.

C1 6800uF 25V Electrolytic Capacitor
T1 3A 15V Transformer
BR1 5A 50V Bridge Rectifier 10A 50V Bridge Rectifier
S1 5A SPST Switch
F1 4A 250V Fuse

If you want to use the auto battery charger without having to provide an external power supply, use above circuit. The first time you use the circuit, you should check up on it every once and a while to make sure that it is working properly and the battery is not being over charged. Source: Auto Battery Charger

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