Simple Solar Inverter Circuit with Charger

This post shows you how to build a circuit that can take power from a solar panel and turn it into household electricity AC.

It has two parts: a charger and an inverter.

The charger uses an 18V solar panel to charge a 12V battery.

The inverter uses the battery power to create household current AC through a transformer.

A switch lets you switch between charging the battery and using the battery to power appliances.

What is a Solar Inverter Circuit with Charger:

A solar inverter circuit with a charger is a combination of circuits that allows you to convert solar energy into usable electrical power and store it in batteries.

The primary components of such a circuit include a solar charge controller, an inverter and a battery bank.

Circuit Description:

Parts List:

Circuit working process:

Solar Panel:

The solar panel converts sunlight into electrical energy and provides a variable voltage output depending on sunlight intensity.

The TIP35 transistor is configured as an emitter follower.

In this configuration the emitter voltage follows the base voltage minus the forward voltage drop across the base emitter junction.

The 15V zener diode connected to the base of the TIP35 helps clamp the base voltage to around 15V preventing it from rising too high.

The zener diode acts as a voltage regulator for the base emitter junction.

The output voltage of the emitter follower is regulated to around 14V after accounting for the 0.6V forward voltage drop across the transistor.

This regulated voltage is suitable for charging a 12V battery.

The SPDT switch allows the user to choose between two modes: solar charging and inverter operation.

In the solar charging mode the switch connects the solar panel to the battery for charging.

In the inverter mode the switch disconnects the solar panel and connects the battery to the inverter.

Inverter Circuit:

The 2N3055 transistors are configured in a cross coupled arrangement to create an astable multivibrator or a flip flop circuit.

This configuration allows the transistors to switch states alternately producing an alternating current AC output.

Transformer:

The 9-0-9V secondary winding of the transformer steps up the voltage produced by the inverter transistors.

The primary winding of the transformer is connected to the collector emitter circuit of the 2N3055 transistors.

Battery:

The 12V 25Ah battery serves as an energy storage source.

In the inverter mode, the battery provides power to the inverter circuit, and the inverter produces AC output.

Operation:

• When the switch is in the solar regulator position the solar panel is connected to the battery through the emitter follower circuit.
• The solar panel charges the battery, and the voltage across the battery terminals increases.
• When the switch is in the inverter position the solar panel is disconnected and the battery is connected to the inverter circuit.
• The inverter circuit consisting of the cross coupled transistors and transformer converts the DC power from the battery into AC power.
• The transformer steps up the voltage and the inverter produces an AC output across its secondary winding.

Formulas:

Here with relevant formulas emitter follower circuits primarily deal with biasing the transistor and analyzing its AC characteristics.

1. DC Biasing:

Base Current (IB): Because IB depends on transistor gain (β) and circuit configuration, there is no one formula that can be used to calculate it, although you may approximate it using:

I_B = (V_CC – V_BE) / (R_bias)

where,

• V_CC: Supply voltage
• V_BE: Base Emitter voltage around 0.6V for silicon transistors
• R_bias: Resistor connected between base and voltage source e.g. voltage divider biasing

Emitter Current (IE): The transistors current gain determines how base current and emitter current are related:

IE = (β + 1) * IB

• β (or hFE): Transistor current gain

2. AC Characteristics:

Voltage Gain (Av): The voltage gain of emitter followers is almost 1, it can really vary between 0.8 and 0.999:

A_v = 1

Note:

These formula offer a fundamental comprehension.

Use small signal equivalent circuits, which require more component characteristics for a more thorough examination.

How to Build:

Building the solar inverter circuit components connections process is mentioned below:

Solar Charger Circuit:

• Connect the positive terminal of the solar panel to the base of the TIP35 transistor.
• Connect the negative terminal of the solar panel to the ground.
• Connect the emitter of the TIP35 to the positive terminal of the battery.
• Connect the collector of the TIP35 to the positive terminal of the solar panel.
• Connect the base of the TIP35 to the 15V zener diode.
• Connect the other end of the zener diode to the ground.
• Connect the positive output from the emitter follower to the positive terminal of the battery.
• Connect the negative output from the emitter follower to the negative terminal of the battery.
• Connect one pole of the SPDT switch to the positive output of the emitter follower.
• Connect the other pole of the SPDT switch to the positive terminal of the solar panel.
• Connect the common terminal of the SPDT switch to the positive terminal of the battery.

Inverter Circuit:

• Configure the 2N3055 transistors in a cross coupled arrangement.
• Connect the collector of the first transistor to the base of the second transistor and vice versa.
• Connect the emitter of both transistors to the negative terminal of the battery.
• Connect the primary winding of the transformer to the collectors of the 2N3055 transistors.
• Connect the secondary winding of the transformer to a load or the output you intend to power.
• Connect the common terminal of the SPDT switch to the junction point of the collectors of the 2N3055 transistors and the primary winding of the transformer.
• Connect one pole of the SPDT switch to the negative terminal of the battery.
• Connect the other pole of the SPDT switch to the negative terminal of the transformer.

Testing:

Solar Charging Test:

• Set the SPDT switch to the solar regulator position.
• Ensure that the solar panel charges the battery and the output voltage remains within safe limits.

Inverter Test:

• Set the SPDT switch to the inverter position.
• Check the AC output across the secondary winding of the transformer.

Note:

• Care should be taken to ensure that the components are appropriately rated for the given power levels and safety measures should be considered to prevent over discharging of the battery.
• Additionally, this simple solar inverter circuit with charger should include protective features such as fuses and temperature monitoring to ensure safe and reliable operation.

Safety Precautions

• Include fuses in the circuit to protect against overcurrent.
• Implement circuits or devices to prevent over discharging of the battery.
• Monitor the temperature of critical components to avoid overheating.
• Insulate connections to prevent short circuits.

Conclusion:

This is a basic post, and the actual construction may vary based on specific component values, ratings and the desired power output.

Always refer to datasheets for accurate information on component specifications.

If you are not familiar with electronics consider seeking assistance from someone with experience or consulting with a professional.

Additionally, ensure compliance with local electrical codes and safety standards.

References

Single Phase Solar inverter with smart Charge control

Inverter for the Solar Panel