How to Connect Solar Panels to Multiple Batteries

The majority of solar panel systems rely on multiple batteries.

If connected correctly it increases the amount of energy you can store from your solar panels.

When wiring up your solar panels to your batteries, things can get a little confusing.

There are various cables, voltages, inputs, and outputs to take into account.

But once you understand the relationship between all the components it becomes much clearer.

In an easy-to-understand way, let’s go through the process of connecting your solar panels to multiple batteries.

Connect in Parallel to Increase Capacity

The first thing to get your head around is the way we are wiring up the batteries.

There are two different methods that produce different outcomes.

If you want to increase your battery Ah storage capacity then you want to connect them in parallel. (That’s what we’ll look at here.)

The other option is to connect them in series but this will result in a higher voltage and capacity will stay the same.

For example, let’s say you have two 12V 100Ah batteries. When these are connected together you get this result:

Connected in parallel = 12V 200Ah (Increased Ah overall)

Connected in series = 24V 100Ah (Increased V overall)

Connecting Solar Panel to Multiple Batteries Step-by-Step

Let’s go through how you will hook up your batteries and solar panel. 

Step 1 – Wiring Diagram

Before you start work you should draw your wiring diagram so you have an overview of where everything sits in your circuit. This way you will have a clear plan before you start. 

Here is a diagram for you to work from:

Solar panel and battery wiring diagram

The system is made up of 3 major sections and this is the order in which to connect them: 

  1. Batteries that connect to the charge controller 
  2. Solar panels that connect to the charge controller 
  3. Power Inverter that connects to the batteries

Throughout the process, we will always be matching up our connections ‘positive to positive’ and ‘negative to negative’ 

Step 2 – Wire Your Batteries

When working on the batteries you should wear gloves and safety goggles as they contain harmful acid and can spark. It is very important to protect your eyes.

So we are going to connect our batteries in parallel.

  1. Place your batteries side by side in the position you will keep them in. 
  2. Using battery cables connect all the positive (red) terminals in a string. 
  3. Then connect all the negative (black) terminals in a string.

 It should look like this:

Batteries wired in parallel

You will see that all the positive terminals a linked in a line and the same for the negative terminals.

  1. Finally, run a battery cable from the final positive battery terminal and wire it to the + battery input on the charge controller. Then do the same for the negative to the – battery input on the charge controller.
Connect batteries to solar charge controller

Now you have multiple batteries connected in parallel.

Step 3 – Connect Solar Panels

Always connect your batteries to your charge controller before your solar panel. Otherwise, the energy from a solar panel can destroy the charge controller as it has no output.

At this point, if you have multiple solar panels you can connect them together in parallel just like we did with the batteries.

To connect your solar panel to the charge controller you will need MC4 adaptors. These are positive and negative cables with an MC4 connection at one end and a stripped wire at the other. 

  1. Plug the MC4 solar panel outputs and the adaptors together. Positive to positive and negative to negative.
  1. Next, wire the stripped ends on the adaptors to the charge controller solar panel input. (Red to + and black to -)
connect solar panel to solar charge controller
  1. You should now have a reading on your charge controller and your solar panel can start charging the batteries.

Step 4 – Connect Your Inverter

The final thing to do is to connect your power inverter. This will draw 12V DC from the battery and convert it into 120V AC to run your appliances.

You should connect the inverter directly to the batteries, not to the charge controller. This is because the amps drawn by the inverter will be too much for the controller to handle.

  1. Put your gloves and safety goggles back on before working on the batteries.
  1. Connect the inverter to the same terminals you connected the charge controller. Hook up the red inverter cable to the red battery terminal. Then the black cable to the black terminal. 

Final Words on Connecting a Solar Panel to Multiple Batteries

Hooking up multiple batteries to your solar panel is not complicated. You should have no problems if you follow the step outlined in this article. 

Of course, some equipment can vary. So use this as a guide and check your components before you start for the best procedure.

To be honest, once you have the batteries wired together correctly, the process is exactly the same as connecting a solar panel to any other battery.

Just remember to connect your charge controller to your batteries before the solar panel. Then hook up your solar panel and once the sun arrives you’ll be ready to rock.

That’s it! Enjoy the sun’s free energy wherever you may be.

Looking for recommendations on what equipment to use? Check out my guides to the Best Solar Charge Controller and Best Off-Grid Solar System.