Can You Connect Charge Controllers in Parallel? (Yes, Here’s How)

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A parallel connection for solar panels is commonplace, but can you do the same with charge controllers? The answer is yes, you can. In fact it is the most practical solution for off the grid systems with large solar arrays and batteries.

Solar charge controllers can be connected in parallel to meet the requirements of high powered solar systems. The controllers may be connected to the same battery bank, but they must have separate solar sub arrays.

Requirements For Charge Controller Parallel Setup

Before you do any set up, make sure the following requirements are met:

  • Several solar controllers can be connected in parallel, but each one must have its own solar sub array.
  • Controllers can be connected to one battery bank, but their sub arrays must be separate.
  • If using an MPPT controller like the Renogy 40A Rover, individual sub array tracking is ideal.
  • The battery bank capacity must be sufficient for the number of controllers used.
  • Each solar sub array must be set according to the specifications of its controller.
  • Controllers in a parallel connection can be different sizes but must be the same type. For example, you can use a 20A and 30A PWM controller, but you cannot use a PWM and MPPT together.
  • Each controller should have a battery temperature sensor. Not all controllers have it, but it is ideal.
  • The controller charging profiles have to be similar.
  • Make sure the battery and charge controller wire sizes are correct.

These guidelines are for information purposes only. Refer to your charge controller manual for additional details on how to set up a parallel configuration.

How to Connect Charge Controllers in Parallel

The following example assumes you want to connect two charge controllers to one battery bank. Remember that solar controllers must have their own PV array. The other assumption is that the battery bank is the right size for your system.

  1. Connect the positive wire of controller 1 to the positive terminal of the battery. Repeat this step with the positive wire of controller 2.
  2. Do the same with the negatives. Connect the negative wire of controller 1 to the negative terminal of the battery. Repeat this with the negative wire of controller 2.
  3. Connect the positive wire of controller 1 to the positive connector of solar array 1.
  4. Plug the negative wire of controller 1 to the negative connector of solar array 2.
  5. On the second PV array, repeat the steps above with controller 2, connecting the positive and negative controller cables to the positive and negative connectors on the array respectively.

If you want to install an inverter, connect it to the battery via the cables supplied with it. For the best results, keep the cables as short as possible.

The batteries, controllers, inverters (if installed) and solar panels should be as close to each other as possible. The closer they are, the less energy is lost in cable transmission.

After all the components have been installed, place a load on the solar panel or inverter. The load should run fine if the installation was correct. A check of the system monitor will show you that the power capacity has been increased.

Can You Connect PWM Controllers in Parallel?

Yes, you can link up multiple PWM charge controllers in parallel. However most prefer MPPT because it is more efficient. But there are good PWM controllers available including the Pow Mr 30A Solar Controller.

Connecting two or more PWM controllers in parallel is similar to an MPPT. The controllers can share a single battery bank, but each must have its own solar sub array. The wires should be connected in the same manner as given earlier in this guide.

Whether it is PWM or MPPT, the controller must have its own PV array to ensure there is no conflict. If the controllers are connected to the same battery, they will combine forces so to speak, and regulate the charge flowing into the battery.

PWM controllers can be different sizes. Just make sure that the controllers support the type of battery whether it is gel, AGM or lithium ion. No matter which controller you choose, the batteries and panels have to be properly connected.

There are those who voice concern over using multiple controllers. But there should be no serious issue provided the wirings are correct. As long as the battery can accept the output of all the controllers, there is no problem.

The solar panels provide the energy and it is coursed through the batteries. The charge controllers make certain the right amount of current goes through. With a proper setup, the battery will not overload, overheat or overcharge. The controllers do not supply the power, it is the battery.

The Benefits of Charge Controller Parallel Configuration

A charge controller can only handle a certain amount of charging power. By connecting two or more in parallel, its capacity increases and becomes more efficient. If your system needs more power, a parallel connection is recommended.

Other benefits of installing another solar controller:

  • You want to increase power
  • Need to install additional solar panels
  • You want to install a PV module with specs different from what is in the current array
  • You need to create two separate solar arrays to maximize sunlight hours

A parallel controller connection is ideal for battery banks that require lots of charging power. Majority of MPPT solar controllers are designed to work with large scale batteries used in large homes, solar powered buildings, cabins and other off grid systems.

Batteries can be charged from two or more sources and that includes solar controllers. The more chargers used, the higher the current and the faster the charge.

For a parallel configuration to work, the battery bank maximum current must be capable of handling the controller output. You can find this info on the battery manual or manufacturer website.

Charge controllers may be combined with other chargers like AC power or generators. You could set up a system where the solar controller does regulation charge while the generator or AC does bulk charging.

Modern MPPT controllers have voltage regulators that coordinate and match the charging. The top brands also work with third party systems to ensure smooth operation.

How Charge Controllers Work Together

Charge controllers have different features depending on the manufacturer, but they share some common characteristics. Once configured the system needs very little input from you, but knowing the factors that affect performance helps.

Charge controllers can detect the state of the battery, specifically its resistance. The controller goes into bulk charge mode if resistance is low. If it is high, the charge is reduced. With two or more controllers, the battery gets charged faster.

The controllers either communicate or use SOC (state of charge) to regulate the voltage. This ensures the controllers work in unison and go through the various charging phases correctly.

Each controller profile should be the same, including the various settings. You can customize multiple controller settings and save them to ensure stability.

Controllers have a connector from the battery that leads to their respective voltage sensor. This feature allows multiple controllers to measure the battery voltage the same way.

Some controllers today have a temperature sensor. This enables each controller to gauge voltage temperature. Not all systems have this feature, but it helps to have these especially with outdoor battery setups.

Batteries are sensitive to heat and it has a direct effect on performance. This is one area where temperature sensors can help. Another is during the boost charging phase.

When the battery enters the absorption / boost phase, the controller has to lower the voltage. Controllers in parallel will restrict the voltage at the same time provided the settings are similar. A temperature sensor is going to make this process more reliable.

Differences in Absorption Charging Speed

You might notice that one controller may run the absorption charge faster than the other. This can happen, but it has little to no effect on the battery health.

If a controller has not completed the charge, it will maintain the voltage and finish the cycle even if the other controllers have moved on to the float. In some cases the controller may be able to supply sufficient current, and the voltage will end up at the float.

If any problems should arise the controller will notify you. Its display screen will show any error message, and you can use that information to fix the problem.

Conclusion

As solar systems become more powerful, the need for two or more charge controllers has increased. If you plan to set up a large solar array and battery bank, knowing how to put together a parallel setup for your charge controllers is essential.