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.

Schematic

This is the schematic of the Car Battery Charger

Parts
Part
Total Qty.
Description
Substitutions
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

Notes

  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
    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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Comments

TARIQ
Car Battery Charger
Monday, May 04, 2009 10:43:37 AM
Thanks for your circuit, It is very simple and easy to built, Can i charge a car battery 12V40Ah ?
Eric K
Battery charger/maintainer
Sunday, April 05, 2009 7:05:42 AM
I just bought a battery maintainer for $20 at a local shop and have seen similar items elsewhere for similar money. Google for "battery maintainer". I see Home Depot has a Black and Decker one listed for about that. Cheaper and a little less bulky than a full on battery charger.
OSCAR
Car Battery Charger
Saturday, April 04, 2009 6:42:14 PM
Thank you for the circuit
anonymous
Car Battery Charger
Thursday, March 19, 2009 12:40:56 PM
I need a battery charger that will allow me to charge up my battery, while drawing from it 12volts @ 6 amps intermittent. What unit do you recommend that will not allow ac to come into my two way radio? In other words, I want my battery to be topped off, while keeping the charger hooked up to it. Is this possible? Your suggestions/comments, etc. Thanks, Chuck
anonymous
Car Battery Charger
Wednesday, March 18, 2009 6:03:51 PM
Just make sure the transformer or the input voltage gives at least 5A or else you won't get 5A out of the LM338. However, I am wondering if I can use a general comparator (LM339) instead of the LM301, it seems to work better when simulated in Multisim. -Nick
George
Charge a device of 23V battery from a 24V car battery
Thursday, March 05, 2009 6:45:13 AM
I was wondering if I can charge a 24V lead acid battery from another 24V lead acid battery. Can I remove the charge from one battery and transfer it to the other? If yes, which electrical device could do this? Thank you
Dark
Car Battery Charger
Monday, February 16, 2009 12:01:59 PM
Can I replace the LM350 with an LM338T? To get 5A current
alberto
Car Battery Charger
Thursday, January 29, 2009 11:16:57 AM
Hello, I have to charge a lead/acid battery 6V 140Ah (!!), will this circuit functioning? Which part should be modified? Thank you
oscar
Car Battery Charger
Friday, January 09, 2009 5:16:31 PM
good diagram.
ray fok
Car Battery Charger
Wednesday, December 24, 2008 11:53:48 AM
I have a 20-year old car battery charger (12 volts) still in good condition. My question is : can I still use it to charge a late model car battery ?
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