How to: wire a campervan electrical system

How to wire a campervan

Wiring and installing the electrics is arguably one of the most complicated and daunting jobs in your van conversion. We spent a long time reading blog posts and forum comments and watching YouTube videos to try and figure out exactly what we needed to know. Here we talk through everything we did in our own Sprinter camper van electrical system, the products we bought, and everything we learnt along the way so that you can learn how to wire a campervan electrical system.

Contents

DISCLAIMER: We are not electricians, and everything we did in our own van we figured out by researching online. We hope the information is useful to you, but is not professional advice. Electricity can be dangerous, and if there is anything you are not sure about, make sure to consult an electrician.

Campervan electrical system components

Below is a list of all of the electrical components we bought for our campervan electrical system. We’ll go into a little more detail later as to how to wire a campervan, as well as how we decided on battery size, number of solar panels, and the size of our inverter.

Main components

Component Quantity Link
180Ah Varta Professional flooded lead acid batteries
2
Victron Energy MPPT 100/50 charge controller
1
Victron Energy BMV-712 smart battery monitor
1
Sterling 800W 12V quasi sine wave inverter
1
12V fuse box
1

Solar setup

Component Quantity Link
100W Renogy solar panels
3
Renogy solar MC4 Y branch connectors
1
Renogy cable entry housing
1
Solar panel fixing kit
1

Lighting components

Component Quantity Link
3W spotlights (230 lumen, white finish, warm white)
10
Triple rocker switch & pattress box
1
Double rocker switch & pattress box
1
Fairy lights
1

Wires, connectors & wiring accessories

Component Quantity Link
150A bus bar
1
Kill switches
3
Arctic F12 PC fans
2
Double rocker switch and pattress box for fans
1
Midi fuse holders
4
125A, 2x 100A & 50A midi fuses
1
3-40A blade fuse set
1
Plug sockets & pattress boxes
4
Red and black wire (various lengths and thicknesses)
-
Yellow, blue and red crimp connectors
100s
Cable lug eyelets
10s
Cable lug hydraulic crimp connector
1

How to size your campervan electrical system

The amount of electricity you expect to use in your campervan will affect the size of battery you need. We worked this out by making a list in a spreadsheet of all the appliances we planned to use in our van, and then calculating the Amp hours for each appliance using the following equation:

Watts / volts = Amp hours

Where the volts equal 12V, the voltage of your batteries, and watts equal the wattage of each appliance. Once you have the Ah for each product, you will need to multiply by the number of hours you estimate the product to be in use for each day. Adding all of these together will give you your total estimate Amp hour usage per day.

We calculated our absolute maximum as 110Ah/day. As you should never let your batteries discharge less than 50%, you then need to double this, which equals 220Ah.

As we didn’t want to rely on a) our solar panels fully charging our batteries each day (in case of cloud/rain) or b) having to drive around each day so our split charge relay could charge our batteries, we were keen to go for larger than a day’s worth of energy. In the end we went for 2x 180Ah Varta flooded lead acid batteries which gave us a total of 360Ah.

Camper van electrical system in a van conversion

Once we had decided on battery size, we then worked out how many solar panels we would need in order to charge our batteries. Before, we worked out the Amp hours that we would be using with all of our appliances. To work out the size of our solar panels, we needed to work out total watt hours:

Watts x hours = watt hours

So if a 30W product is in use for 3 hours, the total watt hours would be 90. Once you have worked out your total watt hours for all your products, you’ll need to divide this by the average amount of full sunshine your solar panels are likely to receive in a day.

We worked out our maximum would be 1500Wh, so dividing this by 6 hours of sunlight we worked out we would need 250 watts of solar panel power. We decided to buy 3 100W Renogy solar panels to give us 300 watts of power.

Our campervan wiring diagram

Our campervan wiring diagram can be used to understand how to wire a campervan.

Our system consists of:

  • Power coming in via a split charge relay and a solar charge controller

  • Power going out via a 12V fuse box and a 800W 12V inverter

We chose to install an inverter in our campervan electrical system so that we could have 230V power in our van. This meant that we could wire in standard plug sockets so we could charge laptops, phones, and anything else mains powered we might want to plug in, and it also meant we ended up wiring in 230V lights. Below is a list of the appliances we’ve wired into our camper van:

12V appliances:

  • Lights in the boot
  • 2 fans
  • Fridge
  • Water pump
  • Water level sensors
  • Diesel heater
 

230V appliances:

  • 3 double plug sockets
  • 1 single plug socket
  • 10 3W spotlights
  • Fairy lights
  • Sparker for hob

Important note about split charge relays: If you have a Euro 6 engine you will not be able to use a standard VSR (voltage sensing relay) to charge your batteries, as they have a ‘smart’ alternator which drops below 12V after around 30 seconds, meaning it will not provide the required voltage to a VSR to charge your leisure batteries. You will instead need to purchase a B2B (battery to battery) charger to charge your leisure batteries from your starter battery. Although there are other options available (such as the Durite 0-727-43 ‘smart’ VSR, these are not advised as they can damage AGM and gel batteries due to overcharging.

How to wire a camper van electrical system

How to size your inverter

Your inverter will take the 12V power coming from your batteries and convert it to 230V so that you can run regular AC appliances such as laptop chargers.

There are 2 types of inverter available:

  • Modified sine wave
  • Pure sine wave
 

Modified sine wave inverters are much cheaper than pure sine wave inverters, and should work fine for around 95% of AC appliances. Occasionally modified sine wave inverters can make a buzzing noise when certain appliances are plugged in. We went for a modified (quasi) sine wave inverter.

Depending on what you plan to use in your van will decide what size inverter you need. The calculation you will need to do for each appliance is:

Voltage x amps = watts

Once you have done this calculation for every appliance you plan on running on 230V in your van, you will have the total watts that could be in use at one time.

Then, to play it safe, and future proof your electrical system…double it. The number you now get is the minimum watts you’ll need out of an inverter to power all of your appliances at the same time.

We worked out our total watts at 350W, so we went for the Sterling 800W quasi sine wave inverter. This way if we ever want to run more powerful appliances in our van, we still have plenty of leeway.

However, it’s worth noting that not every 230V appliance will be able to be used with an inverter. A good inverter will have a mechanism built in which will stop it from providing power to an appliance which exceeds the total wattage in order to protect the inverter, but not all inverters will have this so make sure you check every appliance before plugging it into your van.

girl wiring a camper van electrical system

How to wire a 2 way light switch

A 2 way light switch controls a light from 2 different sources. We were keen to wire our 4 bedroom spotlights and fairy lights into a 2 way system so that we could control them both from the 3 gang light switch by the van door (which also has a 1 way switch to control the main 6 spotlights), and from the 2 gang light switch by our bed. We knew this was making things complicated for ourselves…but we’ve never been good at making things easy!

Below is a wiring diagram for how to wire a 2 way switch. As well as running a ‘power’ wire from your 12V fuse box or your inverter (depending on if you have 12V or 230V lights) to your switch, and wire from your switch to your lights, you will also need to purchase 3 core + earth cable to run between your light switches. This has a black, grey, brown and earth wire. You will need to connect the negative of the power wire and the negative of the light wire together outside of the light switch.

Thanks for reading, if you have any questions feel free to drop us a message on here or via Instagram!

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how to wire a campervan electrical system

14 thoughts on “How to: wire a campervan electrical system”

    1. It will depend on the distance between your lights and your fuse box and also the amp rating of the lights you purchase, but typically 1.5mm2 cabling should be sufficient. You’re best ordering from eBay as B&Q tend to be really expensive for most things vs buying online!

  1. Great blog guys, very informative and really well presented. I just had one question: Is there a reason why you went for the 50amp solar charge controller with a 300w solar system? From reading around it seems that 30amp would do the job, but I may be missing something… Is it so you have the option of adding more solar panels in the future? Cheers!

    1. Hi Dom, thanks for your message! When calculating the size of your solar charge controller, you should add a 25% factor of safety to the current of the solar panel. So the panels are 5.72A each, which with a 25% safety factor added is 7.15A. This makes the total input current of the three panels 21.4A, so we went for the 100/30 charge controller. Hope that helps!

  2. Hi, I absolutely love your van. The layout that I came up with is actually 80% the same as yours! (I still have to build it tho) I have a medium wheelbase van so I’m still trying to figure out how to sleep lengthwise I was thinking of making an extendable bed that you can pull out and rest on the backseats of the couches. So besides that my question about this article is can you please explain how you wired the wall plug sockets (the 230V ones) to the inverter? Do you just use a 3 wire AC cable? did you use a breaker box (consumer unit) with AC rcd’s? If so what Amps and what wire size? Did you connect several in parallel? does this effect the rcd amp size? I’m sorry for the many questions but I have been looking everywhere for a good explanation and can’t find it anywhere. Hope you will be able, anyways again very nice camper and happy travels!

    1. Hey, thanks for your message! Yes, you should wire any plug sockets into the inverter via a consumer unit containing RCDs or MCBs as protection. This essentially acts like the 12V fuse box does for the 12V circuit. You can either wire each plug socket into its own RCD/MCB, or you can wire them in a ring circuit and connect them to a single RCD/MCB. You will need to use 3 core cable that’s a suitable thickness for the distance you’re covering in your van, and ensure it’s stranded rather than solid core. 2.5mm2 is usually sufficient for plug sockets, but you’ll need to double check this for the distance you’re planning on covering, as this affects the wire thickness you will need. Typically a 16A MCB can be used for a socket circuit, but it’s worth double checking this for your exact scenario 🙂 hope that helps!

  3. Caroline Schofield

    Hi guys- love the van! Can you explain what you did to the computer fans to wire them into the system as they come with motherboard connector plugs!

    1. Hey Caroline, we snipped the connector plugs off the end and wired it into the 12V fuse box via a switch to turn it on and off. Ours also had a yellow cable which is to control speed, but we didn’t connect this to anything. Hope that helps!

  4. Great post as always guys. Curious where you keep your leisure battery? We’re trying to figure out the electrics just now but don’t want too much cable running from starter battery through the van. Thought it would be best to keep the leisure battery as close to starter battery as possible. So complicated!

    1. Hi Jo, our leisure batteries are inside our bench seating, however if we were to do this again I think we’d put them in the boot space, as it gives them more room to breathe and means they can be next to all of your other electrical components. It’s fairly standard practice to house the electrical system in the boot space of the van. Thanks!

  5. Hi, thanks so much for your blog and insta – it’s helping us loads with our van build! I was just wondering how your downlighter circuit worked. Did you splice the wires and connect in an extra wire with bullet connectors? I’ve heard of different methods (e.g. splicing the wires to add in an extra cable or essentially running the cables in parallel so that you attach 2 wires to each downlight). Sorry if this question is a bit confusing and thanks so much for any help you can provide! Isabelle

    1. Hi Isabelle, yes we did it exactly as you suggested, using bullet or butt connectors to join one light to another using an additional piece of wire to bridge between each light on both the positive and negative sides. We felt that using a butt connector to join the two wires before going into the light was more robust than trying to jam both wires into the connection point on the light. Hope this helps 🙂

  6. Pingback: Electric, Water & Gas – | Robin |

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