Here’s a simple solar battery charger circuit that I used for more than 4 months now and still works fine. The circuit is very simple and easy to make with universal board. It uses the LM317 linear regulator for the charging circuit.
About the circuit:
The circuit is very simple, it only uses LM317 linear regulator to limit the charging voltage to 14.8V. D1 is use to avoid the LM317 to draw current from the battery when the solar voltage drops below the battery voltage. Change D1 if you think that the charging current will go above 1A. In my case I used 1N5400.
Calibrating:
If you notice I used trimmer instead of a fix type resistor. This is to have set the output more accurately. To set the output of the regulator, remove the battery and turn on the LED light connected to it. Adjust the trimmer until the output voltage becomes 14.8V.
Caution:
Some safety tips:
- For safety, you can connect a fuse to LED light, battery and Solar cell output.
- Make sure the output of the solar panel used is less than 1.5A. LM317 regulator can only handle up to 1.5A.
BUILD:
Conclusion:
For sure this is not a good implementation but I only created this project because this is easier than designing a complex charger. I have no enough time to design and build a better solar charger but I am planning to build one in the future. The circuit is not efficient and it waste power because it uses a linear regulator. Switching regulator will be better for charging battery for solar but this one does the job with less effort to build one.
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