Dual Mode Inverter Battery Charger

Here is a dual charger for Inverter battery. It can charge the battery via Solar panel as well as from AC power to keep the battery always in top condition. Even though a 12 volt Solar panel gives around 20 volts in full sunlight, it is available only three or four hours in a day. During the remaining hours, the intensity of light is very low and the condition worsens in cloudy and rainy days. This results in incomplete battery charging that ultimately leads to memory effect and permanent damage of the battery. This charger shifts the charging to AC mode when the voltage from solar panel reduces below 12 volts and restores the solar charging when the sunlight is sufficient enough again.

The circuit uses a voltage comparator built around IC1. It is powered by the voltage from the solar panel and ZD1 provides 12 volts regulated supply to the circuit. Its Inverting input is referenced at 10 volts using a 10 volt Zener while the Non inverting input receives a variable voltage through R3, VR1 and R4. When the solar panel gives more than 12 volts output, pin3 of IC1 gets a higher voltage than pin2 ( as set by VR1) and its output turns high. T1 conducts and the relay energizes. The battery gets charging voltage through the Common and NO contacts.

Click Image to get enlarged view

When the solar panel output reduces to 12 volts, output of IC1 turns low and the relay de-energizes. Then the battery charges through the Common and NC contacts of the relay. The NC contact is connected to the Transformer power supply using a 15-0-15 volt 1 Ampere transformer .If the switch S1 is closed, the AC charging continues during night also.

9 responses to “Dual Mode Inverter Battery Charger

  1. Pingback: PowerFilm 28w Rollable Solar Panel Charger

  2. SIR…………..,

    Actually in present situation every body using
    Inverter- Battery – Charging circuit mainly depends on normal available 230V A.C. Supply only. The battery terminal is permanently connected with Inverter terminal. So if you are change the circuit in such a manner , the battery can accept both way of charging simultaneously
    ( Normal A.C.Supply as well as solar charging source ). then it is very useful one………………

    I have mentioned some points here for the kind perusal please.

    (1). But depends on availability of any one charging source, another source (either normal AC Supply or Solar ) disconnect automatically it self from the circuit.


    (2). Both the source is simultaneously used for battery charging without any problem.
    ( Battery charging time is reduced so much…..)

    (3). We must avoid manual disconnect Battery from the normal inverter charging circuit and reconnect it to Solar charging circuit.

    I expect a good reply sir…………….

  3. SIR……………….. !!!
    Thank you so much…..
    I have already have 800VA sukam inverter with 160 AHr. AMCO made Battery. I need a solar charger circuit wanted in parallel with the normal 230V AC supply charger. Can you help me………….. ?
    If so THANKS in Advance tooooooooooooo

    R A M ” S

    • Hello Ramachandran
      I think the circuit above will satisfy your requirement. It delivers around 1 amps current from the transformer. Battery capacity and charging current has no relation. If it is 12 volt battery, use a 15-0-15 or 0-15 volt transformer 2 or 3 ampere rating. The battery will take around 1-2 amperes(If it is good) initially then it drops to 500 mA or less during the remaining period. Since the inverter battery is always connected to charger slow charging with low current is ideal.


  5. Dear Sir, Thank you very much for very useful circuit especially for the current situation in tamilnadu(India). I am planning to use 300 or 400 watt solar panel to charge my existing 12V 150Ah battery (850VA Microtek Inverter). I have some basic questions & clarifications…Kindly advice.
    1. I need to use atleast 30A solar charge controller to charge my battery..can i just connect the output of charge controller directly to replace the solar panel. I have concern about higher current flow.
    2. What happens when power fails during day time (whenthe solar output is 12 or 12+ volts)..the relay energizes and battery is connected with NO..Inverter needs battery to discharge or to invert DC to AC. Battery + terminal is engaged with solar panel side. Am i right? This may be very basic or annoying question. Sorry for that! Kindly advice.