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This is very simple but good enough lead acid battery charger. I am using it many years with great success.

The charger has charging current limiter and short circuit protection.

The incandescent Light Bulb at the primary of the transformer do not allow the current at the secondary coil of the transformer to rise up more than the light bulb wattage will allow. The light bulb is acting like current limiter!


It is simple but excellent!

The charge time for empty battery depend of battery capacity (Ah) and the current which transformer can deliver (the power of the transformer)

If the transformer output voltage is 32V AC, then this simple charger can be used for charging any lead acid battery from 6V to 24V. You just need to select a light bulb with the appropriate wattage for the desired charging current according to the diagram below. Then connect the charger to battery (regardles of the battery voltage) and the charger will start charging the battery!

I have placed all the elements of this charger in a suitable metal box, and on top of the box I have mounted three light bulb sockets connected in parallel. So, depending on type of the battery and desired charging current, I can easily put one, two or three bulbs depending on desired charging current.

From time to time, you have to check the voltage when battery is connected to charger, and be sure to stop charging when voltage will rise to 15 V (for 12V battery)

You can short Plus and Minus wires of the charger all day long and current will not rise more than incandescent light bulb wattage will allow. That is why I called it automatic charger :-)




The idea is taken from the book "Mala Skola Elektronike" (d-r Vladimir Krstic)

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Mile Kokotov (2022)

MIle Kokotov, M.Sc. is industrial engineer manager and has a master`s degree in technical science with almost 40 years expirience in RF-technics. He is Acttual President of The Radio Amateur Society of Macedonia

Feel free to visit other articles and projects on his website

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