Car Battery Charger
Electronic Schematics > Automotive > Car Battery Charger

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


Part Total Qty. Description Substitutions
R1 1 500 Ohm 1/4 W Resistor  
R2 1 3K 1/4 W Resistor  
R3 1 1K 1/4 W Resistor  
R4 1 15 Ohm 1/4 W Resistor  
R5 1 230 Ohm 1/4 W Resistor  
R6 1 15K 1/4 W Resistor  
R7 1 0.2 Ohm 10 W Resistor  
C1 1 0.1uF 25V Ceramic Capacitor  
C2 1 1uF 25V Electrolytic Capacitor  
C3 1 1000pF 25V Ceramic Capacitor  
D1 1 1N457 Diode  
Q1 1 2N2905 PNP Transistor  
U1 1 LM350 Regulator  
U2 1 LM301A Op Amp  
S1 1 Normally Open Push Button Switch  
MISC 1 Wire, 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.

This is the schematic of the Car Battery Charger Power Supply


Part Total Qty. Description Substitutions
C1 1 6800uF 25V Electrolytic Capcitor  
T1 1 3A 15V Transformer  
BR1 1 5A 50V Bridge Rectifier 10A 50V Bridge Rectifier
S1 1 5A SPST Switch  
F1 1 4A 250V Fuse  

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.

Title: Car Battery Charger
electronic circuit
Published on: 2005-02-02
Reads: 2864
Print version: Print version

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Electronic circuits > Automotive > Car Battery Charger