solar charger circuit schematic

Solar Charger for 6V Battery

Here is a solar charger circuit that is used to charge Lead Acid or Ni-Cd batteries using the solar energy power. The circuit harvests solar energy to charge a 6 volt 4.5 Ah rechargeable battery for various applications. The charger has voltage and current regulation and over voltage cut-off facilities.

The circuit uses a 12 volt solar panel and a variable voltage regulator IC LM 317.
The solar panel consists of solar cells each rated at 1.2 volts.
12 volt DC is available from the panel to charge the battery. Charging current passes through D1 to the voltage regulator IC LM 317. By adjusting its Adjust pin, output voltage and current can be regulated.

Schematic of the Solar Charger Circuit

solar charger circuit schematic

Solar charger with current regulation and cut off.

video presentation of the working circuit with a 6V battery

VR is placed between the adjust pin and ground to provide an output voltage of 9 volts to the battery. Resistor R3 Restrict the charging current and diode D2 prevents discharge of current from the battery.

Transistor T1 and Zener diode ZD act as a cut off switch when the battery is full. Normally T1 is off and battery gets charging current. When the terminal voltage of the battery rises above 6.8 volts, Zener conducts and provides base current to T1. It then turns on grounding the output of LM317 to stop charging.


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  • Ajay

    Plz tell me sir erickshaw roof panel price and bulk panel send rate list only panels and all it am price

  • Josephs Christian

    Please Sir, how do you calculate the base resistance used alongside the Zener diode to switch on the cutoff transistor? Thanks.

  • Bijit

    Sir I want to make a solar lamp and my solar panel configuration is 7V 0.1mA and we want to charge NI MH thee cell battery total is of 4.5V. So please tell what are the changes requied in this circuit.

  • ashutosh

    Sir ,
    I have a 5.8 v solar panel and I want to charge li-ion battery (2010 Mah) what should be the circuitry and equipments I will require for the same..

    Thanx in advance…

  • sandeep

    i have toshiba c-640 laptop and 10w solar panel .on the charger of laptop marked output is 19v 3.42A .
    can i use this circuit diagram to charge a laptop? and can i add a voltage divider in this circuit a 5, 16,19 and 21 volts output? can you help me.

  • Afsorul Haque Barbhuiya

    Hi sir,
    I want to use a solar panels having capacity of 12 volt that can provide sufficient energy to charge a battery of 8.4 volt. Also I want to charge my smartphone by using solar power because my mobiles charger connector has been corrupted , so please sir help me to initialize the system that can provide sufficient energy to charge my smartphone with out connector .Please sir……..

  • Zoals

    I’ve done this circuit for 6 volts 4.5aH battery, LM317 gives max 7 volts with 12 volts 10W solar panel or 12 volts 1A transformer.

    So thinking some thing wrong I have done another circuit which is also giving same 7 volts output even after adjusting VR.

    Please let me know the issue.

  • vinay

    solar charger for 6volts battery was good but if the battery over charge what should be done can you please explain sir what should be done

    • sleniofernandesyahoo-in

      Hello Mr. Vinay, I had a similar question like yours. I wanted to know how to upgrade this circuit bye adding LEDs to show the charging process and charged process.

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  • Benoit

    Is it possible to use this to charge 4 cells of 1.4v?
    Please tell me about thé components zener résister?
    Is a solar panel provided 6v good?

    • Jim Keith

      I recommend this circuit instead:

      While it is intended for charging a lead-acid battery, it works OK with other battery types as well. However, it is harder to set the voltage with other types of batteries –one method is to charge them via the usual means, connect to the solar charger and adjust the voltage for perhaps a 10mA end of charge current.