Simple Electrical System for a Van Build

In this article, I describe and explain the solar electrical system in our van conversion from a detailed diagram that helped me build and connect everything to the equipment I used and why I chose it. You will find here the tools I used, the equipment and gear needed and how to connect everything so that it works and is safe. This simple 12 V solar electrical system for a van build may not be perfect, but it is functional and has all we need for our home on wheels; it is perfect for us. 

I am in no way a professional electrician or engineer. This article describes our system and how it was put together. I am not responsible for improper use of gauge, fuse, components or tools. Always use caution when working with electrical components.

*Discloser: This article may contain affiliate links, meaning I may receive a small commission at no extra cost to you if you purchase through a link. More information

Converting a van is an exciting adventure. It can also be a challenging one. Planning the van conversion helps when it comes time for the build. When it comes to the electric components in a van conversion, the options are endless. I hope this description of my van 12V solar power electric system will help simplify this task in your build.

Tools I used while working on the electrical system in my van build

Most of the equipment and tools I used were bought on Amazon. When Amazon did not offer what I needed, I made a trip or two to Canadian Tire and Home Depot. Most hardware stores carry the necessary tools to build a van’s simple electrical system.

Solar Panels for a Van Build Solar System

I installed two Renogy 100-watt monocrystalline solar panels on the roof for the van-build solar system. So far, there has been plenty to recharge the batteries every day. They are easy to install with the mounting brackets specially made for this. 

Renogy Solar Panel Kit including 2 solar panels, charge controller and fittings

Check price on Amazon

Mounting the Solar Panels

I installed the mounting brackets on the solar panels. You will need 4 for each panel. Then, I placed the two panels where I wanted them on the roof of the van and marked the roof where I needed to drill the holes for the screws. Next, I drilled through the roof at the marked spots and replaced the panels to screw them in place. Finally, I used lock washers and nuts to secure the screws from inside the van. 

installing solar panels in the roof of the van for the solar system
drilling wholes in the van roof to install solar panels for the solar system

I also added Gorilla silicone sealant and Gorilla waterproof seal tape over the screws on the roof to completely seal the holes made from the screws and avoid leaks inside the van when it rains.

I drilled one more hole in the roof, where the cables from the solar panels come in the van. Here, I recommend using the double cable entry housing mount from Renogy. It is sealed and waterproof. 

Wiring the Solar Panels

This solar panel kit also comes with the 30A Wanderer charge controller, which is essential to protect the batteries mainly from overcharging. This kit also includes the MC4 adaptors and a pair of Y-branch connectors to connect the panels to the charge controller. 

I wired our solar panels in parallel (more on that below) using the Y-branch connectors. The positive and negative cables enter the housing mount and go through the van’s roof through the drilled hole. The hole is under the waterproof mount, so I don’t need to worry about leaks. I used silicone around the mount to seal it completely.

I bought extra 10AWG cables needed to get from the roof to the charge controller under the bed in the van. Also, I added a 15A Renogy fuse to the positive cable between the panel and the controller to protect the system.

Calculating the fuse size for two 100w solar panels

Figuring out the size of the fuse for the system will depend on the number of panels and whether they are connected in parallel or series. The fuse rating = the total amperage x 1,25 (25% safety factor).

Our system has 2 x 100w panels in parallel (doubles the amperage), each 5 Amp (2 x 5 = 10Amp total).

10Amp x 1,25 = 12,5 rounded up to the next available fuse size, so a 15A fuse will protect the system.

The voltage doubles if the solar panels are connected in series, but the amperage stays the same. This would make the calculation 5 Amp x 1,25 = 6,25, rounded to the next available size, a 10A fuse.

diagram of solar panels connected to charge controller with fuse on the positive cable

Then, I connected each cable (the positive and the negative) to the appropriate slot on the charge controller. 

wanderer charge controller with the solar panel cable slots circled

Solar panels in parallel or in series?

After reading and learning about building solar systems, I chose to connect my two panels in parallel. Solar panels connected in series will have more voltage and charge your batteries faster. This is because they work as one large panel. However, if one panel is partly obstructed, the system will be compromised, and the batteries won’t charge as efficiently. This does not happen when the panels are connected in parallel. If one panel is obstructed, the other will charge the battery as it does not depend on the other, like when connected in series.

Series Wiring:

  • increase voltage
  • same amperage
  • panels are dependent on each other’s capacity or performance

Parallel Wiring:

  • same voltage
  • increase amperage
  • panels work independently from each other
  • needs cables that can accommodate the higher amperage
  • more expensive to wire

Batteries for the Van Build Electrical System

I use two deep-cycle AGM 12 V batteries in my simple electrical system. They are connected in parallel to increase the amperage giving a total of 150 amp/h. I used 2AWG cables to wire the batteries in parallel.

The deep cycle was essential to me. I don’t need to worry about draining my batteries to the point of compromising their life span. 

The batteries are also sealed, which makes them safer; no acid leaks and no gas emissions. And no need to refill them with water. Lead-acid batteries have to be filled. Additionally, they must be in a ventilated container as they emit a gas that can be harmful. 

The batteries are connected to the charge controller. Two cables run from the appropriate slot from the controller to the batterie’s appropriate terminal. Negative to negative and positive to positive with 10AWG cables.

wanderer charge controller with the battery cable slots circled

For the fuse on the positive cable, I used a 10AWG cable with blade fuse holders and a 30A fuse. The fuse matches the charge controller amperage. A cable runs from the negative terminal to the van’s chassis for grounding.

Diagram of solar panels connected connected in parallel to the charge controller and batteries connected in parallel

Fuse Box

My simple electrical system includes the BlueFire fuse box.

fuse box with wires coming in and the labels for each wire

Buy on Amazon

The batteries connect to the fuse box, negative to negative and positive to positive. Another cable goes from the box’s negative terminal to the van’s chassis for grounding. I used 10AWG cables for those connections. Again, I used a 10AWG cable with blade fuse holders and a 30A fuse on the positive cable.

diagram of batteries connected in parallel and wired to fuse box

Each 12V appliance in the van connects to one positive terminal on the fuse box and one negative terminal on the negative bus bar integrated into the fuse box. 

The gage of the cables will depend on the load and how long the wires are from the devices to the fuse box. See the description below for more details on wiring each appliance to the fuse box.

Tip: Use the shortest cables from each device to the fuse box and the same length for one appliance’s negative and positive wires.

Bluefire fuse box wiring in a van build electrical system

Items I used to connect the appliances to the electrical system in my Van Build:

Wiring the Lights

The van has six pot lights in the ceiling and two light bars under the bed at the back in the commonly known van’s garage. 

The pot lights are wired in parallel. Both the negative and the positive cables are connected to a dimmer switch with 22AWG cables, and from the switch, a positive 18 AWG cable goes to the fuse box and the negative one to the bus bar on the fuse box. The positive cable connects to the fuse box with a 5A blade fuse in the appropriate slot.

diagram of pot lights connected in parallel
diagram of the pot lights wiring

The pot lights below are the ones I bought and installed. They come already wired in parallel and connect to a device that, in turn, I connected to the dimmer. This made it easier as I did not have to wire each light separately. They light up the van, and we usually use them dimmed down as they can be bright, so I recommend using them on a dimmer like the one I used below.

The light bars are installed under the bed platform in the van’s garage. Each bar has 22AWG positive and negative cables that run from the bar to the fuse box, with a 2A fuse for each light.

These two lights are practical when we need something in our storage space under the bed. Think of any place where a light would be helpful and add it to your plan if possible.

Wiring the Roof Fan

Implementing a roof fan in a van conversion is imperative. Air circulation will go a long way in avoiding damage from moisture build-up. Once the fan is installed, you need to wire it to your electrical system. Here is how the roof fan in our van conversion is wired.

I used a 14AWG positive cable approximately 7 feet from the fan to the fuse box and a negative cable of the same length and gauge to the bus bar. The fan is protected with a 5A fuse, but I added one in the appropriate slot on the fuse box as an extra precaution.

Wiring the Fridge

The 12V fridge in our van build sits on a platform that slides in and out from under the bed. It is easy to access. It connects to a 12V outlet I installed under the bed close to the fridge. The plug is connected to the fuse box with 14AWG cables and a 7.5A fuse. The refrigerator is close to the electrical system and only requires about 3 feet of cable.

12V fridge ideal for a camper van
12V outlet in a van build electrical system

Wiring the Water Pump

The water pump in the van build is the Onsen 3.0 RV / Marine 12V Water Pump. To set up the pump, I used the diagram in the operating manual. A positive 16AWG cable runs from the pump to an on/off switch and then to the fuse box. A negative cable of the same length connects the pump to the fuse box’s bus bar. Both cables are approximately 3 feet in length. A 10A in-line fuse in the cable protects the device.


Wiring the USB and 12V plugs

I installed a couple of USB outlets and a second 12V outlet in the van. Many electronics, mainly our phones, charge with a USB. I also use it to recharge my earphones, selfie stick, and Kindle. 

With the USB outlets came a voltmeter. The voltage display is handy for monitoring the battery and the electrical system. It was easy to connect it to the fuse box using 14AWG cables with a 5A fuse in the slot.

usb and voltage monitor used in a van conversion electrical system
diagram of 12V electrical system in van conversion
Diagram of my solar electrical system in my van build

Wiring the Inverter

This was a last-minute addition. We had not included an inverter in our plans, but as they say, only fools don’t change their minds… and we are no fools. I installed a 2000w inverter. The inverter includes two USBs and two AC outlets. I am grateful to have it now. We use it to power our projector to watch TV, use the Magic Bullet for smoothies, or charge our laptops.

The inverter has all the equipment needed to connect it to the system and is super easy to install. The positive and negative 4AWG cables connect to the batteries’ appropriate terminals. It also came with the proper in-line fuse holder and a 200A fuse. If the inverter does not include the fuse, I recommend adding one to protect the device and the battery.

Renogy 2000W inverter

Split Charge on a Van Build Electrical System

What is a split charge for a van build electrical system?

A split charge is used to charge the house or leisure batteries from the vehicle’s alternator when the vehicle is running. The alternator, used to charge a vehicle’s battery as the car is running, will simultaneously charge the leisure batteries. It is easy to install and cost-efficient.

Why install a split charge for a van Conversion Solar electrical system?

This type of charging may come in handy when there is less sunlight to charge the batteries from the solar panels (think winter with shorter days, a day of heavy rain and cloud cover). The house batteries can charge as you are driving. The downside of this system is that you must remember to kill the switch when the vehicle is turned off so as not to drain the vehicle’s starter battery. 

What I used to set up the split charge in my 12V electrical system

Isolator switch connected to 2 gauge cables

How I installed a split charge for my van-build electrical system

The cable runs from the van’s starter battery on the positive terminal to the back of the van on the house battery’s positive terminal. A kill switch or isolator switch is necessary on that cable. Once I decided where I wanted the switch (easy access), I ran the cable from the van’s starter battery to the switch and then from the switch to the leisure battery in the back of the van.

As a precaution for the batteries and the electrical system, I recommend using an in-line fuse between the van’s starter battery and the kill switch and another fuse on the cable running from the switch to the leisure battery. Both fuses should be as close as possible to the battery terminals.

As mentioned above, you will need to keep the switch off and turn it on only when the van is running and you want to recharge the house battery.

Final Words on this 12V Electrical System for a van build

This van-build solar system is simple, but it covers our electrical needs in this tiny home on wheels. Do not hesitate to reach out if you have questions or comments as you problem-solve through your build. If you are still in the planning phase of your build, this guide to simplifying the planning of a van build will be helpful. I hope you have as much fun building your van as I had converting mine.

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