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Build Your Own Automatic Car Battery Charger


This is a project for those who want to build their very own  Automatic Battery Charger. This is a project made by one of  the member of  Elab Forum, duc_tech. But as a reminder, this circuit don’t have a current limiter which means this charger is good to use only on a known good battery but not on a battery that have defects like having a short or open plates which will cause the diodes, switching Thyristor and transformer to heat easily. As a suggestion by Pinoy_Tech, “Series wire wound resistor is the quick and easy solution, others used series bulb instead.”

Here are some of the pictures of the said project making an automatic car battery charger.

automatic Car Battery Charger

Schematic Diagram of Automatic Car Battery Charger


PCB Board

Top View of the PCB Board

Making the Casing From an ATX Power Supply salvage casing

Project Casing

A transformer made from a re-winded from a defective UPS transformer.

Rewinded Transformer

Transformer and Board

Transformer In the Casing

On Testing Stage

Battery Tester on Testing

Testing Mode

On testing Mode

The finish Product

Finish Product

Final product

Final Results of the Project


The part, SCR1 -S4006LS3 OR S1006LS3, is hard to find locally so try to use TRIAC-Q4010L4
and it works but makes sure that the MT2 pin is the input from rectifier else there will be no output.

Posted by Ronelex 2 Responses

2 Responses to “Build Your Own Automatic Car Battery Charger”

  1. Keshinro Amos says:

    Can the charger charge a 12volt car battery?

  2. E.L. Gabriel says:

    Hello, I came across this site recently. I’ve built several of these battery chargers myself as far back as 2005 when I first acquired an old Arlec 10 amp simple charger and searched the net for some sort of regulation control. I then went about making the control circuit on a 2.5 square inch strip board with fan cooling, volt and amp gauges and led’s. I used tyn816 and c106d SCR’s. It was a great charger it never let me down. I used to take it to work to charge new vehicle batteries over night before delivery. I set float charge to 13.60 volts and the years I used it never boiled a battery. Two weeks ago I built two of the same chargers for my 2 brothers in-law at my wife’s request as a Christmas present without volt gauges, I hope they will appreciate the effort I went through. Thanks, Merry Christmas and a Happy New Year.


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