How to install a campervan solar system

This article is a basic overview showing the steps needed to install a Campervan solar system. To go along with this article, we offer free solar system plans that are designed to be simple, beginner friendly, and expandable. Check out our Free Solar System Plans here.

What you’ll need to build a solar power system

In order to build a solar power system you’ll need to be competent with both A/C and D/C power, or have the help of someone who is. Do not attempt to work with electricity if you do not know what you are doing. Even minor mistakes can get you or someone else hurt or killed. You are responsible for your own safety.

Along with the proper electrical competence, you’ll also need a variety of tools to build these systems. Some of our designs require only basic handtools to connect prefabricated cables. Other designs will require that you fabricate cables yourself using crimping tools. In either case you can Check Out Our Shop to find any tools or electrical components that you might be missing.

Before we begin please understand this basic rule: Always disconnect power from your equipment and turn switches in the off position before doing any electrical work.

Project overview

Before we begin, let’s get an overview of what we’re building. It’s helpful to think of a solar system as being 3 separate sections. Each of these sections will be built separately and at the end, we’ll connect them together.

Building the Battery Bank

First, we’ll install our battery bank.

Always wear safety glasses anytime you’re working around the batteries and make sure that all switches are in the off position.

The battery and inverter cables should be kept short and thick. Since so much current flows through these cables, it’s also very important that each pair of cables stays roughly the same length. A couple inches of difference is generally fine, but a 3 foot positive cable and a 1 foot negative cable is not recommended.

Read our Guide to Wire Selection if you need further help sizing your wires.

Most of our designs use either 12 or 24 Volt batteries wired in a parallel configuration. This keeps the battery voltage the same and adds their total capacity together. We prefer designing our systems with parallel connected batteries because it is more beginner friendly.

Before installing your batteries

Always pay special attention to wiring polarity (positive/negative). A mistake here will lead to destroyed components and possibly a fire. Again, if you don’t know what you’re doing, get professional help.

• Use identical batteries (same age, type, chemistry, and specification) from the same manufacturer when building battery banks.
• Fully charge your batteries before you connect them together.

Batteries with a different state of charge (ie: one charged, one dead) will attempt to equalize, meaning, lots of power will flow from one to another. With LiFePo4 batteries this is especially important. LiFePo4 batteries have very low internal resistance, which means they can release alot of power, very quickly.

Location considerations

When installing your batteries, choose a secure location while considering cable run lengths. The cables going from the batteries to the power inverter should be kept relatively short.

Ideally, you’ll want a space that receives good airflow, but if you’re using LiFePo4 batteries airflow is not critical, just make sure they won’t overheat. If you’re using traditional lead-acid batteries (AGM, Gel, or FLA batteries) it’s critical to maintain good airflow. These types of batteries produce flammable gas, and if enclosed in a non-ventilated area this can pose a fire hazard. For this reason, traditional lead acid batteries should not be mounted in the same enclosure as power inverters or other electrical devices that may produce an arc. Make sure gas can escape upwards and out of the vehicle.

Make sure the batteries are protected from loose objects rolling around. You need to be certain that nothing can accidentally fall on the batteries and loosen or short out the terminals. The batteries themselves must also be securely fastened if you’re installing this system in a camper.

Temperature considerations

In general it’s best to keep your batteries around room temperature. Avoid installing your batteries in engine compartments, or against uninsulated surfaces like sheet metal.

LiFePo4 batteries should not be charged when their internal temperature below 0°C (32°F), otherwise, their charge capacity will be damaged. If you’re using LiFePo4 batteries, it’s best to keep them mounted in an area that will stay above freezing temperatures. They can however, be discharged during freezing temperatures without problems, so you can continue to power devices during freezing temperatures.

If you plan to charge LiFePo4 batteries during freezing temperatures, you’ll need to purchase batteries that have a self heating function. Another, more advanced option is to install heating mats. These mats must be controlled with a thermostat, as too much heat will also destroy batteries.

In any case it is critical to install the temperature sensor that comes with your solar charge controller next to your batteries. This sensor will tell the charge controller when it is safe to charge the batteries.

Making your battery cables and connections

Once your batteries are in position you can start connecting their cables. If you’re you’re using premade cables you can just bolt them up, making sure each connection is tight and secure.

If you’re creating your own cables, experiment with how you will route the cables before doing any cutting or crimping. You want to avoid excessively long cables, crisscrossing, or sharp bends. In general, the cleaner your system is, the easier it will be to maintain, upgrade and diagnose.

When you’re satisfied with how your cables will lay out you can start making your cuts. Make your cables an inch or two longer than required so you have wiggle room to install them. Use a cable lug crimper, quality lugs, and some heat shrink or electrical tape to make your cables.

Your main fuse needs to be mounted close to the main positive cable coming from the battery bank. A good practice is to use a Class T Fuse for a lithium battery bank, be sure to select the appropriate size for your design.

If you’re installing lead acid batteries, you can install an inline ANL fuse. Any wiring between the battery and the fuse is not protected from short-circuiting, so keep this wire length short.

After the fuse, it’s a good idea to install a main cut-off switch. This makes maintenance, long-term storage, and repairs much easier and safer. You can install this main switch on the power distribution board, which we’ll be covering in the next section. After the cut-off switch, you’ll connect directly to the main positive busbar. This busbar distributes power to the rest of your components.

On the negative cable, install the shunt/ battery monitor. All current needs to flow through the shunt, so no components can be mounted between it and the battery bank. After the shunt, the negative cable will connect to the main negative busbar.

Building the Power Distribution Board

Next, you’ll create the power distribution board which from this point forward we’ll simply call “power board”. Do this by mounting as many components as you can reasonably fit onto a board or inside of an enclosure. We recommend using fireproof materials instead of wood whenever possible.

Pre-wiring your components in your house or workshop will save you time and headache later because you won’t be crawling in tight spaces trying to fit everything perfectly. Once your power board is done, you’ll just bring it out to your campervan and connect a few cables to the busbars or switches.

Power board component layout

Layout your largest components first, then the busbars and switches. Experiment a bit with how you will run the cables between components before cutting and crimping anything, and check to make sure that you can fit fuse holders in their appropriate locations. Here are two popular layout ideas.

Pay attention to the fuse locations in your circuit diagram. Fuses must be mounted close to the power source. In the event of a short circuit, the fuse will blow, and anything after the fuse should be protected.

Once you’re satisfied that your layout will work on the power board itself, verify that you’ll be able to connect your battery bank, solar array, inverter, and any other components to the power board later on. If all checks out you can go ahead and start making your connections. Don’t forget to secure your wires using ziptie mounts.

Choosing a location for your power board

When you install this section in your van, pick an easily accessible area with good airflow. During operation, these components will generate heat. This heat needs to be allowed to escape or it should be removed using a DC fan like this one here. A good rule of thumb is to try and keep your electronics at room temperature. If you can’t hang out where they are mounted without being covered in sweat, then it’s probably best to ventilate the area more.

Since your main fuses and breakers are mounted on the power board, you should plan to keep it relatively easy to access. You don’t want to have to dismantle an entire cabinet just to change a fuse, especially at 2 in the morning.

Building the Solar Array

Most of our solar system designs have small solar arrays that are wired in series. Wiring your solar panels in series will raise the voltage of the solar array allowing it to charge your batteries with less available sunlight. Click here to learn more about when to choose a series or a parallel solar panel configuration.

Pay special attention to the voltage of your solar panels. Our designs typically use solar panels that have a Voc of around 20 volts (+ or – 4 volts.) Check the back of your panels to make sure their VOC is correct for the design that you are using.

Mounting your solar panels

To build your solar array you will need 10 AWG solar cable, MC4 Connectors, a cutting and crimping tool, you can purchase these things in our shop. Turn all switches to the off position and use the cardboard boxes that your solar panels came in to cover ther panels while you are working on the system, this prevents them from being energized from sunlight exposure. Only uncover your panels once your work is finished and you are certain all connections are correct.

We recommend mounting your panels to a roof rack or using purpose-built solar panel mounts that bolt onto the roof of your vehicle. A bolted connection is, in our opinion, a safer and more efficient way to mount your panels.

Having more distance between the solar panels and the hot roof will help keep their temperatures lower. The hotter your solar panels become, the less wattage they will produce.

You can, however, mount your panels using plastic mounts, VHB tape, and Sikaflex like many other people do. We just prefer bolts ourselves.

Once your panels are mounted you’ll connect everything using MC4 Connections and Solar cable. MC4 connections are weatherproof and Solar Cable is UV resistant. Pay close attention to the wire polarity (Positive and Negative) while wiring up your panels, reversing or mixing up polarity can lead to a fire.

It’s a good idea to glue some cable mounts to the roof and secure your wiring every 12 to 16 inches. This will help prevent the wires from moving while driving, causing the insolation to rub off.

The solar array cables will enter the vehicle through a cable entry gland and then tie into the power board through the PV Isolator Switch. When you are ready to connect the solar cables to the PV-Isolator, make sure the Isolator is still in the off position.

Once your solar array is installed you can remove the cardboard you used to cover them, however, keep the PV isolator switch in the off position. The solar charge controller must be connected to the battery bank before you turn on the solar array.

Final connections and testing

Now, that the three sections of the solar system are completed, all that is left is to connect them together. Before connecting these sections, turn off all switches.

• Check all the wiring and connections one last time to be sure that everything is tight and correctly installed. It pays to double-check your work.
• Connect the main battery cables to the busbars on the power board. Still keeping the switches in the off position.
• Next, connect the solar cables to the PV isolator, keeping the isolator in the off position.
• Go back to the main battery switch and turn it to the on position. The indicator lights on your inverter, solar charge controller, and DC-DC charger should now light up to show they have power from the batteries.
• Now that your batteries are connected you can flip the PV isolator to the on position. If the sun is shining, your solar charge controller should now indicate that it is receiving solar power.

If everything is functioning properly, spend some time checking the safe operation of all of your components. Use your hands and feel the cables on the DC portion of your system. If they are a little warm during operation that’s ok, but if any cables are become hot they need to be replaced with thicker cables.

Did you find this installation guide helpful? Did you successfully build your first solar power system? Do you think there is something that we left out that should be added to this article? Let us know if the comments, we look forward to hearing from you!