Car Battery Charger

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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.

    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

  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.

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Car Battery Charger
Sunday, April 12, 2015 11:03:44 AM
I am a novice but I built this charger and it works just like it's supposed to. I am going to hook this up to a table fan that I converted to a generator and charge the battery on windy days. Great site.
Car Battery Charger
Friday, October 21, 2011 8:11:48 AM
from the power supply the positive and negative of the supply connects to where in the charger? it only has one "IN" where does the negative of the supply go? the ground goes to the transformer right?
Car Battery Charger
Friday, September 16, 2011 5:10:16 AM
I just know more about car battery. Don't over charge the battery or it will damage it.
Car Battery Charger
Thursday, September 01, 2011 6:59:10 AM
Can i use a 8amp 13.8V voltage regulator as an input supply for the car battery charger?
Car Battery Charger
Wednesday, February 09, 2011 3:17:59 PM
what should the output voltage of the charger be? i got around 15 V according to multisim. thanks
Car Battery Charger
Thursday, October 28, 2010 8:41:28 AM
hi, when saying "most any lead acid battery" do you mean it will charge a 6 Volter too?
Car Battery Charger
Sunday, October 10, 2010 7:04:10 AM
can i use any other diode instead of D1 IN457?help me plz....
Car Battery Charger
Friday, June 25, 2010 1:15:25 PM
Thats a great circuit ! I am gonna use it as a storage battery charger. Thank You
Car Battery Charger
Sunday, June 20, 2010 11:41:25 PM
the circuit that u suggested has 18v input i think it should be DC voltage and as you know a 12v AC transformer after passing throgh a diode bridge give 18v DC( 12x2 root squire). so i think a 12vAC transformer with 3 amp current are enough for this circuit, is it ok?
Car Battery Charger
Friday, May 28, 2010 8:38:17 AM
Nice circuit. what needs to be changed if i want to make it charge a 140 amp battery quckly. I need a 10A to 20Amps charger at least, For my ups, we get 4-5hrs blackout here every day.
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