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How to charge solar batteries with a generator?

If you decide to lay down the use of electricity for a very long time and rely on solar energy, you will need a very powerful solar batteries. These batteries should hold charge for hours when the sun is not available.

There are days when the sun is not available for days. Even with your solar batteries you will need to use other charging methods. 

In our blog today, we are going to focus on charging a solar battery using a generator. We will discuss all the dos and the don’ts of using a generator to charge your solar batteries. Stay tuned. 

Can I connect a generator to my solar system?

A solar PV system is an excellent alternative of reducing the large electricity bill. However, solar energy is not that reliable. You will still need to power your home even when there is a storm or during the winter.

To ensure your home is still running as usual, you can connect any type of generator to your solar system. However, there are a few things you need to know;

  1. Using generator is not free: if you are using generators parallel to your solar PV system you will need to fill the generator with fuel. You will therefore incur some cost. However, the amount you pay for fuel is at least 50% less of what you would have paid for electricity. 
  2. You will need special type of inverters made for generators: Generators burn fuel to produce energy in DC form. You will need a special inverter to convert DC into AC. Generators inverter have the following features;
  • Generator inverters have an inbuilt carbon monoxide detector and safety switch. When fuel burns it produces some gases which are toxic. A CO detector will detect the gas when it’s emitted and shut it down. 
  • These inverters have the capability to reduce noise produced when a generator is running. 
  • Generator inverters ensures the system runs efficiently. You can switch off the inverter to use solar energy stored in batteries. 
  1. You will need a ZED advance controller: ZED advance controller protects your generator from surplus power from solar panels. 
  2. You need transfer switch that separates the diesel generator from the grid. 
  1. Use input#1 with current transformer from the generator.
  2. Input#2 from grid
  3. Connect output#A to input#2 of combiner box 
  4. To send load feedback ZED advance, get a set of current transformer. 
  5. You need 10 Core Cable to connect ZED Advance with current transformers and 3 core cables for sending voltage feedback to ZED Advance. 
  6. You need CAT 5 or CAT 6 Cable for connecting ZED Advance to Solar Inverters and LAN. 
  7. Lastly, you need a LAN connection to connect ZED Advance with the internet.

How to charge solar batteries with a generator?

Charging a solar battery with a generator is not that complicated provided you know the how. This video  will provide you with the required information about charging solar batteries with generators.

I will then give you a step-by-step guide on how to charge your solar battery. 

Step 1: Disconnect the utility grid

If you have a grid-tied inverter system, there are some cables directing to the system. The grid-tied system also has a control panel that allows you to see what goes on in your system.

From the system, there is a switch that allows a charge to enter your system. Switch off the plug. When the plug is switched off, the appliances will continue running with the charge left in the battery backup. 

Step 2: Check the ratings on the generator

Knowing the rating of the generator will help you adjust the settings on the control panel. 

  • On the control panel, set the amount of amps the battery inverter should be drawing from the generator. 
  • As you are running the connections, the appliances will be consuming the charge in the solar battery. This will help you know if the generator is charging once it is connected.

Step 3: Connect your generator

  • Before connecting a stand alone generator to the solar PV system, ensure the generator has enough fuel and also distilled water.
  • Use the plug provided to connect the generator to the grid. 
  • Start the generator and check if there is any input power entering your grid. This can be done by checking the control panel. 
  • Both the generator and the solar panel will be charging the battery. Therefore, the battery will charge faster and you will also reduce the fuel used. 

Step 4: Disconnect the generator

  • Once the solar battery is fully charged, switch of the plug available at the connection between the grid and the generator.
  • Remove the generator
  • Bring the utility grid back.
  • Switch the grid system plug back.
  • Start using your power to power appliances. 

The power that comes from the grid Inverter system is in AC. You therefore don’t need any more equipments.

Can you connect a generator to a solar charge controller?

Most of the generators produces more current an voltage. This might overload your system. To prevent this, add a solar charge controller designed to be used with a solar generator.

A charge controller will reduce the voltage that reaches the solar battery. The charge controller will also regulate the temperatures generated by the generator is when burning fuel. 

How long does it take to charge a battery bank with a generator?

How fast a generator charge a battery bank depends with a few factors;

  • A 12V battery will take up to 2hours to charge fully. However, if it is completely drained it might take 20% more time. 
  • Large batteries will take longer than smaller batteries. 
  • The amount of current you set at the control panel will determine how fast your battery will fill. 
  • If you are charging a battery bank when it is still powering your system, you will definitely take longer than when the battery is only charging. 
  • A battery connected to the solar panels will fill faster than a battery being charged by the generator only. 

Basically, how you long it takes for your solar battery to fill depends on your usage. Ensure you have a charge controller to aid in the battery charging. 


Connecting solar PV system in your home is one thing, keeping the system running is another. Your solar system might stop working due to unforeseen accidents such as storms, winds and even degradation. To ensure the system is still running after this circumstances, install a power backup system such as a generator. 

Although generators are convenient ways of powering your home, you will incur some cost when buying fuel. However, the cost you spend on fuel is way low than what you would have paid for electricity. 

Most grid-tied inverter system provides an option of connecting other systems such as a generator, utility grid and the solar panels. The battery backup will therefore charge with the help of the selected sources. You can shutoff any system you don’t want running when you are charging your solar battery.

The guide above provides the information you need to connect a generator to a solar PV system. 

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