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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  • 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.

  • jonseguin

    Good day Mr. D.MOHAN KUMAR, is it ok if I put a led in series on the emitter of BC548 to indicate that the battery is full? Also putting an LED before or after D1 to indicate that their is a PV source input voltage? thanks for you circuit.

  • amit

    Yes it is tru e…..

  • ben

    is it possible to use this circuit to charge lipo battery ?

    • Kumar

      Charging a lead acid battery and a lipo battery is totally different. Lipo battery chargers have separate charging mechanism.

  • oak floor

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    He was once totally right. This submit truly made my
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  • Brandon

    Does anyone still use this post.

    Also i want to charge a 12v 7ah pb battery. Can i remove the 6v zenor diode and regulate my voltage to 13.8v. What else do i have to remove. Just a basic regulated circuit without compromising the oringinal to much.

    Hope to get a respons.

  • Brandon


    My output voltage is 7.01 is that correct.

    Setup as follows : x2 6v 3w panels in series.
    Input voltage to circuit 13.6v 3w
    Charging a 6v 4ah lead battery

    Isnt my outout voltage to low, my 1k VR is set fully clockwise.

  • Ashutosh Joshi

    I have 4 solar cells 5.5v and 450mA each in parallel. My circuit needs 5v and 1A output . How should I proceed? Will there be a current produced higher than 1A?

  • catalak

    i want to use it to charge cell phone. i have this solar panel. which circuit i must use?
    thank you..

    • Kumar

      This is solar panel with rating of 12volts 5w. You need to use a compatible buck converter.

  • benoit


    I am very interested by this topic and by your device.

    I want to do the same device but with a solar panel, and 4xAA batteries or 9V battery.

    The goal is during solar day recharge the batteries and cut off when there are loaded.

    During night, use the batteries to power a standalone xbee device (need 3,3v).

    On the output of the power device i will put a power regulator to deliver stable 3,3v needed by xbee.

    Is it possible to adapt your device to do mine ?