How to connect solar panels to charge controller in 3 steps

If your solar system has a battery, add a charge controller! It will prolong the lifespan of your energy storage and make your system safer and easier to use. In this article, we’ll take a look at how to connect solar panels to a charge controller.

Charge controller protects your battery

A solar charge controller has to be a part of your system if it has energy storage. Otherwise, you don’t really need it. Here is what a solar controller does:

1. Controls current. It acts like a valve, making sure the current going into the batteries is safe. It also blocks reverse current. At night, batteries can send power back to the panels. The controller stops this from happening, keeping the energy flowing in the right direction.
2. Prevents overcharging. A controller stops batteries from getting too much charge. Overcharging can harm batteries and even lead to overloads or fires.
3. Prevents deep discharge. The controller disconnects batteries from your devices when they are almost empty. When charging starts again, it reconnects them back.

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What is a solar charge controller and how to choose one

If your system is small and consists of only a couple of panels, you might want to get a PWM controller. It simply reduces the panels’ voltage to match the battery's level which is not very efficient. However, it is cheap and durable.

MPPT controller fits any kind of system. It converts extra voltage into current, giving your battery more energy and minimizing power loss. It’s more expensive but it’s the only efficient choice for large systems. Whether you have a PWM controller or an MPPT regulator, the procedure of hooking it up with the battery and panels remains the same.

The size of a charge controller is measured in amps. To choose the right one for your solar setup, divide the total power of your solar panels by your battery's voltage. For example, if you want to connect two 300-watt solar panels to a 12-volt battery, you need a charge controller that can handle more than 50 amps. You should also watch out for the maximum input voltage of the controller.

Gather materials first

The question of how to connect a solar panel to a charge controller usually comes from customers who want to build a small DIY off-grid system on their own. Let’s start by gathering the parts. Here’s what you’ll need:

1. Solar panels
2. Charge controller
3. Battery
4. Wires, connectors
5. Combiner box or branch MC4 connectors (optional)
6. Tools: Screwdriver and wire strippers

Step 1: Connect charge controller to battery

A charge controller usually has two wiring sections: one for panels and one for a battery. Small models may also have a section for DC loads so you can connect a lamp to it if you want.

Wiring a solar charge controller and a battery together is connecting their negative and positive terminals. The charge controller might come with cables already attached for battery connection. If it doesn't, you should use stranded copper wire. Make sure the wire you choose can handle the maximum current your system will carry without overheating or power loss. Use a black wire for the negative terminals and a red wire for the positive terminals. If your wires aren't color-coded, you can mark them with duct tape.

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Solar wire exposed: types and sizes

You'll need connectors that fit the terminals. Common types include ring terminals or lug connectors. If you're uncertain about which ones to use, consult the user manual on your solar charge controller wiring.

Step 2: Start charge controller

Сheck that all the connections are secure, and then turn on the controller. It will initialize and check the battery. The display on a basic controller tells you about your battery's condition and how much charge it has. It will also check the voltage from the panels after you connect them. If you have an advanced controller, you can even set up how you want the charging to happen. Now you're set to wire solar panels to the charge controller.

Step 3: Connect charge controller to solar panels

The junction box of a solar panel has two cables coming out of it. One is positive and ends with a "male" MC4 connector. The other one is negative and it has a "female" connector.

You can remove MC4 connectors from the cables and add connectors for the charge controller instead. Sometimes it doesn’t need connectors, and you can just plug wires into it and screw tightly. Alternatively, you can use two additional cables with MC4 connectors on one end and whatever connectors the charge controller requires on the other end.

When you have multiple PV modules, the process of connecting solar panels to charge controller depends on how you wired them together. If you connect the panels in series, then positive and negative cables from panels on the opposite ends of your array go into the controller. If you connect the panels in parallel, then positive and negative cables go from a combiner box or branch connectors into a controller.

Andrey Gorichenski

Senior Editor

Andrey had been a news editor and freelance writer for a number of medias before joining A1SolarStore team. Climate change and its impact on people's lives has always been among his interests and it partially explains his degree in Philosophy and Ethics.

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