Connecting Multiple Charge Controllers to one Battery Bank

As we know, the solar energy system mainly comprises of

  • The solar panel(s)
  • Batteries
  • Charge controller(s)
  • Inverter

For an efficient system, each component plays its part.

Solar panels capture light and convert it into electrical energy. This charges the batteries, which keeps the solar system working, even at night. An inverter converts the direct current electricity into alternating current energy.

Now the question remains, what does a charge controller do?

A charge controller is a device that:

  • Controls and regulates the voltage and current from solar cells to the batteries.
  • Prevents the batteries from overcharging that can result in severe damage.

Using an MPPT charge controller over a PWM gives the best results.

How to Wire Multiple Charge Controllers?

As you probably already know, you can wire solar panels either in series or parallel.

If you change the wiring you can change the way voltage or current behaves:

  • In series, the current stays the same while the voltage adds up.
  • In parallel, the voltage stays the same while the current adds up.

Sometimes, you will add more solar panels to your system. This is the reason why you would need a bigger charge controller. Logic will tell that you need to discard your old charge controller and buy a bigger charge controller. But what if you could just add another charge controller?

You already know that wiring solar panels in parallel will increase the current. Thus we need to wire our charge controllers in parallel.

If we were to wire them in series, we would charge a 12V battery bank with 24 Volts which will damage the battery.

There is one pitfall you have to avoid and that is that the combined current of the two charge controllers will be healthy for the battery.

For example, each charge controller delivers 20 amps at 14 volts to the battery. this brings up the following question: Is the battery capable of receiving 40 amps at 14 volts? You have to check the battery specifications for this. Look for charging current on the datasheet on the battery.

The cables that leave the ports of the charge controller to the battery should have the same length. This is to minimize the losses in the wires and more importantly, charge them at the same current.

Solar panel to multiple charge controllers and one battery

In the following image you can see how multiple charge controllers with one solar array or string are wired in parallel:

Solar panels connected to multiple charge controllers
Solar panels connected to multiple charge controllers

Strings to multiple charge controllers and one battery

In this example, there are two strings or arrays of solar panels that go to every charge controller. This setup is ideal if you have multiple solar panels that do not have the same rating. Refer to the article about series and parallel wiring solar panels.

You can also use this kind of setup on a boat. If one charge controller is in the shade of a sail, but the other is in full sunshine, the sunny panel will still deliver its max power. The shaded panel will deliver reduced power. This is very similar to wiring your panels in parallel.

Two strings to multiple charge controllers and one battery
Two strings to multiple charge controllers and one battery

Strings to multiple charge controllers and multiple batteries

The setup would be the same as in the first and second example, but instead of going to the busbar, you go directly to the battery terminals.

Synchronizing Multiple Charge Controllers

If you are using two or more charge controllers they do not need to be able to communicate with each other.

Some models are able to do this like the Victron BlueSolar and SmartSolar models. The communication happens with the built-in Bluetooth module for the SmartSolar model. For larger systems, they recommend using the VE.can port.

The reason for communication between charge controllers is so that only one charge controller will balance the cells, not all of them.

Both charge controllers will deliver their maximum amount of current to the battery.

 

Display of bulk, absorption, or float current and voltage levels.

Conclusion

You can wire charge controllers in parallel to support an expanding solar system. You do not need to have charge controllers that are able to talk to each other.

 

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