Battery Charger Circuit using a Solar Panel and 220V Supply

This clever circuit charges your battery with sunshine and regular electricity.

It uses a solar panel to soak up the suns rays during the day and keeps your battery charged.

But do not worry about cloudy days, it can also use regular electricity 220V at night to keep things going.

Plus, it has a backup battery like the ones in smoke detectors so your system keeps working even on super cloudy days.

This way, your battery always has a power source no matter the weather.

Circuit Working:

Parts List:

Solar Power Source Details:

During the day the connected load is powered by either the battery or the solar panel, with the battery compensating if the solar panel output is insufficient.

A single solar cell typically generates 0.5V and around 50mA in bright light rated at 45mW.

A 12V solar panel comprises 24 solar cells connected in series capable of providing 1 ampere in daylight.

For this circuit, a 12V 5W solar panel is used, providing around 300mA current to power the security system and charge the battery.

DC Power Source Details:

Night charging is facilitated by a 12V DC obtained from a 0 to 12V 1 amp step down transformer and a full wave rectifier D3 through D6.

Capacitor C2 filters out ripples from DC to ensure clean power for the security system and the battery.

Resistor R4 provides 80mA current at night for trickle charging the battery while power to the security system is supplied by the battery.

This trickle charging feature saves AC power and protects the battery from overcharging as it receives sufficient charge during the day.

Battery Status Indicator:

This part of the circuit indicates the battery voltage and the solar panel voltage.

Zener diode conducts only when the battery voltage is above 11.6V illuminating the red LED.

The LED turns off when the battery voltage drops below 11V.

If the LED does not light up it indicates either the battery is not fully charged or the solar panel is not providing 12V.

LDR Switch:

This switch controls the DC power supply from the transformer at night.

During the day, the LDR offers low resistance, allowing more current to the base of T1 a PNP transistor, which remains off due to the high base voltage.

T2 also remains off due to the lack of base bias.

At night, the LDRs resistance decreases, making the base of T1 negative turning it and T2 on.

This provides charging current from the emitter of T2 with R4 limiting it to 80mA for trickle charging the battery.

VR1 can be adjusted to set the LDRs sensitivity.

Battery Charger Circuit Setup:

Construct the circuit on a General Purpose PCB and enclose it in a suitable case.

Mount the LDR on the case to receive sunlight and place the solar panel where bright sunlight is available.

Before connecting the battery ensure it is fully charged using a charger.

Formula:

From the above circuit when choosing a solar panel, there are a number of things to take into account including the lead acid batteries capacity, the solar panels output and efficiency and the surrounding circumstances.

The following formula will lead you through the procedure:

Determine the Charging Current Needed:

The charging current needed for lead acid batteries is usually a small portion of their capacity.

It is generally advised to charge batteries at a pace between 10% and 20% of their capacity.

Let us say I_charge to represent the charging current.

I_charge​ = 0.1 × C_battery​

You may get a conservative estimate of the charging current using this formula.

Based on the specifications of the application or the manufacturers recommendations for your particular battery, adjust the multiplier (0.1).

Establish the Required Solar Panel Output:

Watts are used to rate the power production of solar panels.

You may use the following formula to determine the size of solar panel required to supply the necessary charging current:

P_solar​ = ​I_charge​​ / V_solar

where,

• P_solar is the solar panels power rating expressed in watts
• I_charge is the charging current in amperes determined in step 2
• V_solar is the average voltage of the solar panel, typical values, based on setup vary from 12V to 24V

Note:

You can figure out the right size solar panel and charging rate for your lead acid battery system by doing these computations and processes.

Depending on the demands of a particular application or the surroundings, adjustments could be required.

How to Build:

To build a Battery Charger Circuit using a Solar Panel and 220V Supply you need to follow the below mentioned steps:

• Connect the solar panel to the battery via a diode D2 1N4007 to prevent reverse current flow.
• Connect the transformer output to the bridge rectifier D3 to D6 and then to the capacitor C2 for filtering.
• Connect the battery to the load.
• Connect the Zener diode in parallel with the battery to indicate battery voltage.
• Connect the LEDs to the zener diode for battery status indication.
• Connect the LDR to the base of T1 and collector of T1 to the base of T2 for switching the transformer power supply at night.
• Connect a leg of VR1 to LDR and the other to ground.

Additional Steps:

• Mount the LDR in a position to receive sunlight during the day and darkness at night.
• Adjust VR1 to set the LDR sensitivity.
• Enclose the circuit in a suitable case, ensuring proper ventilation for the transformer.

Note:

Building and working with electrical circuits can be dangerous.

Ensure you have the necessary knowledge and take appropriate safety precautions such as using insulated tools and working in a dry environment.

If you are not experienced with electronics consider seeking help from a professional or someone with expertise in this area.

Conclusion:

To conclude kindly remember when working with high voltage circuits it is essential to take necessary safety precautions such as using insulated tools working in a dry environment and avoiding contact with live circuits.

If you are not experienced with electronics, consider seeking help from a professional.

References:

Solar Battery Charger Circuit

Problem with charging battery with dual power supply