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How to Size MPPT Solar Charge Controller? Find Out Now!

Written by Philip Lopez / Fact checked by Paul Lemaire

how to size mppt solar charge controller

Traveling in an RV will be a perfect choice for you to enjoy outdoor camping. The RV offers full appliances like a permanent house, including television, internet, gas stove, grill, etc. so that we have more entertainment besides camping. However, to use these electrical types of equipment, you need to park your vehicle at the RV parks and connect it with community services.

Currently, we have more choices in using energy for our RV and one of which is solar energy. Why does it become the best replacement among all available options and how to use it conveniently? In this article, I will answer these questions to help you understand more about solar energy.

Table of Contents

Understand about RV Solar Charge Controller


Do we need to answer why solar energy becomes the best electrical replacement? Because it is a cheap, clean, sustainable, renewable, and resilient energy source. The appliances of RV require a lot of energy, depending on their occupancy. If you use available options provided by RV parks, you have to pay some extra money to use them. Nonetheless, if you take advantage of solar sources, you won’t need to worry much about the excessive fee or difficult assembly in connecting electricity to your RV.

To create an electric current offering for your RV, we should prepare a solar power system with solar panels. The panels often used in this case have a capacity of 100 Watt. Many campers have integrated a lot of panels to produce stronger electricity. So, to deal with this large electrical power source, we need a material that can reduce the voltage from solar panels to your RV. That is an RV solar charge controller.

The charge controller is known as an electronic bridge to regulate the level of voltage in and out. Our RV is designed with a battery system to get solar energy from panels with a capacity of lower than 20 Watt. Unless we equip the controller, the battery pack may burn out when it receives electricity over 20 Watt.

On the market nowadays, it has two kinds of solar charge controllers:

  • Maximum power point tracking (MPPT)
  • Pulse width modulation (PWM)

The biggest difference between MPPT and PWM is that the MPPT is more effective than the other. It can help your solar system increase 30% more energy.

How to Size an RV Solar Charge Controller?


Besides equipping pieces of knowledge about the charge controller, you need to know some physical formulas to get a suitable assembly for your RV. Because the MPPT controller is the most common today, I will provide some information about how to size the MPPT solar charge controller. Often, you will have two choices to determine the voltage of the controller, referring to the manufacturer’s sizing tools on the websites and applying some quick formulas.

Some elements you should know before making smart calculations:

  • The wattage of solar panel
  • The battery pack voltage (12, 24, or 48)

The first formula is Ohm’s Law: Watts = Volts x Amps

Example: (total wattage of solar panels is 2000 watts) / (24-volt battery pack) = 83.3 amps. Hence, the controller you need should have a capacity of over 83.3 amps. There are three types of controllers: 60, 80, and 96 amps. In this case, you absolutely should choose the 96 amp charge controller.

On the other hand, if you want to know how many solar panels should be used when you have known the amperage of the solar controller.

The second formula: (the amperage of the controller) x (the voltage of the battery pack) = the wattage of the solar system. The most common solar panel is 100 Watt, so you can find the number of panels that should be used.

Example: 60 amp controller x 48-volt battery pack = 2880 Watts of solar panels.

How to Connect The MPPT Solar Charge Controller?

When you have bought the solar charge controller which is suitable with the wattage of solar panels and the battery pack, these are steps that you can refer to connect the MPPT controller:

Step 1: Open the cover of the connection lock, you can see wiring terminals. Once loosen the connection lock, you can see them from left to right are solar, battery and load. Their two sides have a RS485 port for PC and a temperature sensor.

Step 2: Connect battery pack of RV to battery position on connection lock of MPPT controller. The positive terminal of the first battery will be connected to the positive terminal of the charge controller. Then, link other batteries together. The negative terminal of the last battery will be connected to the negative terminal of the controller.

Step 3: Connect the DC load to the solar controller at the load position.

Step 4: Connect the solar system to the MPPT controller at the solar position. Remember to connect the positive and negative terminals of them in the right way.


Those steps above are used to calculate the levels of MPPT energy and learn how to install it. The product is related to the flow of electricity, so you should be careful while working with it.

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