solar inverter battery charger

12V Solar Inverter Battery Charger

Here is an energy saving solar inverter battery charger. It harvests solar energy to replenish 12 volt inverter battery. It has auto cut off facility to stop charging when the battery attains full charge. The charger uses a 24 volt solar panel as input.

The circuit uses a variable voltage regulator IC LM 317 to set the output voltage steady around 16 volts. Variable resistor VR controls the output voltage. When the solar panel generates current, D1 forward biases and Regulator IC gets input current. Its output voltage depends on the setting of VR and the output current is controlled by R1. This current passes through D2 and R3. When the output voltage is above (as set by VR) 16 volts, zener diode ZD2 conducts and gives stable 15 volts for charging.

Charging current depends on R1 and R3. Around 250 to 300 mA current will be available for charging. Green LED indicates charging status. When the battery attains full voltage around 13 volts, Zener diode ZD1 conducts and T1 forward biases.

This drains the output current from the regulator IC through T1 and charging process stops. When the battery voltage reduces below 12 volts, ZD1 turns off and battery charging starts again.

Solar Inverter Battery Charger Circuit Schematic

solar inverter battery charger

Connect the circuit to the solar panel and measure the input voltage. Make sure that it is above 18 volts. Connect the circuit to the battery with correct polarity and adjust VR till LED lights. This indicates the conduction of ZD2 and output voltage. Use heat sinks for LM317 and TIP 122 to dissipate heat.

Note : The same circuit can be modified for charging different types of batteries. The only modification required is the change of ZD1 and ZD2. Select ZD2 value for the required output voltage and ZD1 for cut off voltage level. For example for 6 volt battery, ZD1 should be 6.1 volts and ZD2 6.8 volt. For Mobile battery, ZD1 should be 4.7 volts and ZD2 5.1 volts. All the other components remain same.


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  • altair880gmail-com

    According to Colin Mitchell … this circuit does not work. The output does not rise beyond 11.8 Volt no matter the input voltage. The LED always stays on. They should have armed it before publishing it. It is a waste of time and materials.

  • jacksuraj-surajgmail-com

    Respected Mohankumar;
    iam Suraj – Electrical and Electronics Engineer from Bahrain, my humble request could you please send me the 12 volt solar inverter circuit – which can charge 16.2 volt battery (parallel connected 2.7 volt batteries (2.7 x 6 = 16.2 volt)) respectively,
    thank you

  • jacksuraj-surajgmail-com

    Respected Mohan kumar,
    kindly send me the materials required for the project 12V Solar Inverter Battery Charger to charge 16.2 volt battery , to
    thank you,

  • Colin Mitchell

    mohnkumar is not here any more. He cannot help you as he does not know anything about electronics.
    Just connect the panel directly to the battery via a diode.
    If you use the battery every night, it will get charged every day.

  • shafqat

    respected mohnkumar
    i am from pakistan
    my requriements for a solar controler charer are
    solar panel 150wtt
    Isc=9.08 ampere
    to cahrge a battery of
    12 volt AND 95_AH .

    The circuit should stop work when the battery is charged , and start work when the battery is discharge.the battery charging should be safely.

    i need urgently a circuit with along their calculation and working of each componenti n detail in the circuit.
    each component lternative (at least 1 or 2).
    my email is
    if you are salling such circuit plz urgently email me .

    sir tell me what modification is needed in this circuit.for such a requirment.

  • Colin Mitchell

    The circuit obviously does not work.
    Look at the 100 ohm resistor !!!!!!!!

  • Amos

    @colin have tried this circuit?

  • Colin Mitchell

    The circuit above does not work AT ALL

    Just connect the panel directly.
    No charger is going to tell you when the battery is full.

  • Amos

    I want a controller that protects overcharging, discharging of the battery and shows when the battery is full.

  • Colin Mitchell

    Why? It does nothing.

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