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How to connect a solar panel to a battery in 3 steps

Want to store your solar energy for a rainy day? Add a battery to your PV system. Don’t forget the charge controller so it won’t explode! Let’s go over how to connect a solar panel to a battery in this quick article.

Step 0: Gather your equipment

To pair a PV system with energy storage, you’ll need to gather the equipment. We’re not connecting anything yet so this step doesn’t really count. Here is the list of the basic things you’ll need:

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

A charge controller is a must when you have a solar battery in a system. It protects your battery from the high voltage of panels. If you connect solar panels to a battery directly, it might simply overheat and explode. A controller also prevents overcharging and the state of deep discharge. 

There are two types of charge controllers:

• PWM controllers. They are cheap and last long. You can only use them when the voltage of panels is slightly higher than the voltage of a battery because they simply cut down the voltage to the level of the battery.
• MPPT controllers. They are more expensive but more versatile and efficient as well. An MPPT controller transforms excess voltage from panels into current. Your battery gets more energy and power losses are lower. 

The size of a charge controller is measured in amps. To find the right controller for your solar setup, divide the total power of your solar panels by your battery's voltage. For example, if you’re wondering how to connect two 300-watt solar panels to a 12-volt battery, get a charge controller that can handle more than 50 amps. Watch out for the maximum input voltage of a controller as well.

Depending on how you decided to connect your panels together, the system might have additional equipment. When PV modules are wired in parallel, the wires from them go into a combiner box or branch connectors.

Step 1: Connect charge controller to battery

It’s recommended to connect the controller to the battery first before wiring it with solar panels and not the other way around. Many controllers perform an initialization when they first connect to a battery. The startup sequence helps the controller recognize the battery's voltage and capacity. If you connect the solar panel to controller first, it may not initialize correctly.

Sometimes, the charge controller already comes with pre-attached cables that you can use to connect to a battery. Otherwise, use stranded copper wire. The wire size should be able to withstand the maximum current the system will carry. 

Connect the negative terminals of your battery and charge controller with the black wire, and the positive terminals using red wire. If you don’t have colored wires, mark them using duct tape. You'll need connectors that match the terminals. Common types include ring terminals or lug connectors. Check the instructions for your charge controller when in doubt. 

Step 2: Start charge controller

Check the connections and turn on the controller. It should recognize the battery and evaluate the charge. Now you’re ready for connecting solar panels to a battery.

The display of the most basic controller shows the current state of your battery and its charge. It will also measure the voltage from the panels once you connect them. With advanced models, you can program the charging process to your preference. 

Step 3: Connect charge controller to solar panels

A standard solar panel has a junction box with two cables coming out of it: one is positive with a "male" MC4 connector and the other one is negative with a "female" connector. To connect your panels to the charge controller, you may need two additional cables with an MC4 connector on one end and the type of connector required by the charge controller on the other end. Sometimes there isn’t a connector for a controller: in that case, just plug wires into it and screw tightly.

What if there is more than one panel? If you connect the panels in series, then you’ll have a positive and a negative cable from panels on the opposite ends of your array that you can use. If you connect the panels in parallel, then positive and negative cables come from a combiner box or branch connectors into a controller.

This sums up how to hook up a solar panel to a battery. Once you connect the panels, the charge controller should be able to measure the voltage from them. Keep in mind that panels start to generate electricity as soon as they are exposed to sunlight.

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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