Feb 19, 2013


This charger will quickly and easily charge most any lead acid battery. The 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. 

This is the schematic of the Car Battery Charger



Total Qty.
R11500 Ohm 1/4 W Resistor
R213K 1/4 W Resistor
R311K 1/4 W Resistor
R4115 Ohm 1/4 W Resistor
R51230 Ohm 1/4 W Resistor
R6115K 1/4 W Resistor
R710.2 Ohm 10 W Resistor
C110.1uF 25V Ceramic Capacitor
C211uF 25V Electrolytic Capacitor
C311000pF 25V Ceramic Capacitor
D111N457 Diode
Q112N2905 PNP Transistor
U11LM350 Regulator
U21LM301A Op Amp
S11Normally Open Push Button Switch
MISC1Wire, Board, Heatsink For U1, Case, Binding Posts or Alligator Clips For Output


  1. The circuit was meant to be powered by a power supply, which is why there is no transformer, rectifier, or filter capacitors on the schematic. There is no reason why you cannot add these.
  2. A heatsink will be needed for U1.
  3. To use the 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.
  4. If you want to use the charger without having to provide an external power supply, use the following circuit. 
  5. 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.
This is the schematic of the Car Battery Charger Power Supply

Total Qty.
C116800uF 25V Electrolytic Capcitor
T113A 15V Transformer
BR115A 50V Bridge Rectifier10A 50V Bridge Rectifier
S115A SPST Switch
F114A 250V Fuse

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