How to Set Up a Solar Charge Controller for a Battery Bank

A Charge controller is an integral part of a solar system. It regulates the irregular voltage coming from the solar panel to a reliable voltage and pushes that power to your battery to either boost or trickle charge the battery. A MPPT controller would also be tracking the voltage for the maximum power point ensuring you get the most power from the panels at any given time.

We have listed some easy quick steps to setting up your charge controller that ensures safety for your controller and system.

  1. Select a Surface for Mounting

    Select a Flat Vertical surface where the controller will be mounted. This area should be away from direct sunlight and water. It is also have good ventilation with ample room above and below (150mm) and away from any source of high temperatures.
    Also ensure there is enough room for the wiring.

  2. Mount the Controller

    Use the Controller to mark the areas on you surface for drilling. Drill holes in the marked locations. Secure the controller using the mounting screws. Make sure not to screw too tightly.

  3. Hook the Battery

    The battery should be the first thing you connect to the Battery. You should NEVER connect a Solar Panel to the Controller without a Battery. The charge controller should be clearly labeled for ‘BATTERY + and -‘make SURE the polarity is correct.

  4. Connect to the Solar Panels

    The charge controller should also be labeled for a ‘PV INPUT + and -‘. This is where you hook up the panels. Make sure not to mix up the positive and negative Positive (+) is usually red, while negative (-) is usually black. If you are not sure you can check polarity using a multi meter.

  5. Connect Accessories

    At this point you can connect the Temperature Sensor if the controller has one or if necessary.

  6. Fusing

    Ensure at least 2 fuses that go in between the charge controller and the battery and the controller to the panels. This will protect you controller from any surges in the system.

  7. Programming

    Depending on your system you may need to customize settings to suit your battery which includes setting up parameters for the type of battery. Always use the recommended settings for batteries from the manufacturer. Some controllers can be programmed right from the controller LCD display screen while others might require an App or computer program to set custom parameters.

Solar Panel Sizing and Wiring

The Solar panels may come with MC4 connectors. Don’t cut these connectors as it may void the warranty.  Rather buy two extension cables with bear sides and one with male and female connector. Use the bear side to connect directly to the controller.

To connect multiple solar panels in series join the Positive to negative terminal or in parallel positive to positive. There should be one one positive and one negative terminal at the end of the array to connect to the solar panels.

Note that when using Parallel wiring the amperage from every solar panel is added and this gives the amperage of the system. Make sure that this does not go beyond the rated amps of the controller. In a Series connection the current is divided by the total number of panels while the voltage is added up. Again the Voltage should not go beyond the rated voltage of the controller.

If you want to add more solar panels than the rated amps on the controller, you can add another controller and parallel it to the first controller.

Battery Voltage

While the first step to the process is connecting the battery to the controller. This is after you ensure that the battery voltage is higher than 6V for a 12V system and 18V for a 24V system. Otherwise, the controller can detect the battery voltage.

The controller should have a system voltage recognition mechanism to recognize whether it’s a 12V or 24V system. This is determined by how you wire your batteries. Battery systems can go up to 36V and 48V. Ensure your controller can support the system setup.

You may still need to set battery type (whether Sealed, Flooded or Gel) and capacity in amp-hours. There are also options for user-defined settings and parameters where you can change to suit your batteries. This is especially important if you are using lithium batteries.

Load

You will find a load option on the terminal of a solar controller. This is not just for any load but must be a DC power device with the same working voltage as the rated voltage of the battery. Do not connect an inverter to the load terminal as the inverters have surges that might blow the controller.

Some controllers have 5V output for small loads like lights and light chargers.

Wire

Under sizing the wiring is a really bad mistake to make while they may be drops in voltage because of bigger wire better safe than sorry. Do not use a 10 AWG wires on 30 amp controller or system for that matter.  30 amps will warm up the wires and you would need something around 6 AWG.

LED Indicators

The LED indicators can help detect errors in the system and if there’s any short circuiting in the system it will flash to indicate. If the system is working it will show the charging status. Some controllers have two separate indicators for the PV and for the battery. Reference the controller’s manual to see what the colors of the indicators mean. Different controllers use different colors to indicate errors of if the system is working.

Mounting

A controller may have 20-40 amps of current flowing through it at any given time. This produces a great deal of heat. This heat must be dissipated other the charge controller will fail. This is why it is recommended to choose a controller with a good heat sink. Also ensure to mount the controller where there is good ventilation.