How to connect solar panels to inverter and battery in 3 steps
- 27 Sep 2023
- 5 min
If you want to build a solar system for your RV, boat or off-grid house, you’ll almost always need an inverter. In this article, we’ll cover how to connect solar panels to inverter yourself and why you should add it in the first place.
Inverter turns DC from solar panels to AC
Disclaimer: This article only covers the basics of how to connect solar panels to inverter in an off-grid system. Grid-tie and hybrid systems aren’t DIY-friendly: not any inverter can be used and you have to know the laws and regulations in the area to perform the installation yourself.
Solar panels by themselves produce direct current (DC) under sunlight. Direct current can power lights or a fridge but it’s not suitable for sensitive electronics like laptops or TVs. That’s why you’ll need a solar inverter to convert direct current to alternating (AC). An off-grid inverter has a socket that you can plug your appliances in just like if it were a wall outlet at home.
Normally, you don’t directly connect solar panels to inverter. The voltage of PV modules, even when wired in parallel, is too high for a small off-grid inverter. The inverter will work but high voltage is not healthy for it. That’s why we usually connect solar panels to the charge controller which is wired to the battery and the battery is then connected to an inverter.
Step 1: Connect charge controller to batteries
Use a stranded copper core wire to connect the battery and the controller. Match the negative terminal of the controller with the battery "minus". Likewise, connect the positive terminals. Make sure the wire is thick enough to carry the current. Some controllers come prewired and you can connect them to the battery straight away. Check the manual for info on an appropriate fuse for the controller if there isn’t a built-in one. The size of a fuze is usually the same as the size of the controller in amps.
Read alsoSolar wire exposed: types and sizes
Once you connect it to the battery, turn on the charge controller and let it perform the initialization sequence. It should be able to recognize the battery and measure its charge.
Step 2: Connect charge controller to solar panels
The junction box of a solar panel has two cables with MC4 connectors coming out of it, a positive and a negative. The “male” MC4 connector marks the positive cable, and female connector is on the negative one.
If you have just one panel, you can remove MC4 connectors and wire these cables straight into the controller. Alternatively, take two wires with a complementary pair of MC4 connectors, connect them to a panel and wire the other ends into the controller: positive into "plus", and negative into "minus".
If you have multiple panels and you wired them in series, you’ll have a positive and a negative cables coming from different ends of array. If you wired your panels in parallel or in series-parallel, all positive cables and all the negative cables are grouped together in a combiner box or with MC4 branch connectors.
Step 3: Connect battery to an inverter
Battery or batteries should be as close to an inverter as possible to minimize power losses. Use thick battery cables to connect the terminals of a battery and an inverter.
Consult the manual for your inverter and check if you need a fuse or a circuit breaker in between an inverter and a battery. Some inverters already have a built-in fuse so there is no need for a separate one.
Test your system
With that last step, you’ve finished connecting solar panels to inverter. Turn the inverter on, check the connections and test your system. Solar panels start producing electricity as soon as they are exposed to sunlight.
Remember to take care of your solar system. Read our article “Solar inverter installation and maintenance tips” to learn more!
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