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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.


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
Victron Energy MPPT 100/30 charge controller
Victron Energy BMV-712 smart battery monitor
Victron Energy 800W pure sine save inverter
12V fuse box
Consumer unit

Solar setup

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

Lighting components

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

Wires, connectors & wiring accessories

Component Quantity Link
150A bus bar
Kill switches
Arctic F12 PC fans
Double rocker switch and pattress box for fans
Midi fuse holders
125A, 2x 100A & 50A midi fuses
3-40A blade fuse set
Plug sockets & pattress boxes
Red and black wire (various lengths and thicknesses)
Yellow, blue and red crimp connectors
Cable lug eyelets
Cable lug hydraulic crimp connector
How to wire a camper van electrical system girl wiring a 12V fuse board blue sea systems

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.

campervan leisure batteries girl wiring a campervan electrical system victron

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.

Once we knew how many solar panels we needed, we worked out the charge controller we needed. We did this by combining their maximum voltage, as voltage is added and amperage stays the same when solar panels are wired in parallel. To understand more about solar panels and whether you should connect them in series or parallel, check out our page dedicated to solar panels.

If you’d like help sizing your solar panels and solar charge controller, try out one of our new calculators:

Solar panel calculator

camper van solar panels

Charge controller calculator

Climbingvan Victron solar charge controller illustration

Our campervan wiring diagram

campervan wiring diagram electrical system van conversion how to wire a camper

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 (shown as a B2B in the wiring diagram) 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 via a consumer unit 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 batteries, in particular AGM and gel, due to overcharging.

girl wiring a 12V fuse board in a campervan electrical system how to wire a campervan electricsal system board victron

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.

Climbingvan Victron inverter illustration

Not sure what size inverter you need? Use our inverter size calculator:

victron energy battery protect solar charge controller and orion dc dc converter battery to battery charger in a campervan 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.

how to wire a 2 way switch wiring diagram two way 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

34 Responses

    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. Hi Tom, we installed our electrics after insulating but before cladding. This means that if you ever needed to access your wiring, you would be able to remove some cladding to reach it 🙂 hope that helps!

    2. Hi. My question is simple but I do not know the answer, can you help. My VW T5 van has two existing light in the rear. They have 3 cable going into the lights (brown, brown & red, and brown & black). I would like to swap these lights for spotlights but the new light only have two cables ( red and black). What do I do with the third cable. Do I earth it to the metal of the van or canI ignore it altogether?

      1. Hi there, it’s likely that the existing light is wired into your vehicle’s starter battery. It’s a good idea to run any lights and other appliances off a leisure battery rather than your vehicle battery as you could end up draining the starter battery and not being able to start your van. Hope that helps!

        1. Thanks for your reply and yes I am going to run all lights etc off a leisure battery. Its just that with these two existing lights, I want to change to spots. But like I mentioned they have 3 wires whereas the spots have two. What do I do with the third wire coming from the starter battery. Can I safely discard it? Or should I earth it to metal?

          1. Hi Paddy, unfortunately we wouldn’t be able to comment on the existing cabling, I’m not sure what the brown wire would relate to. Usually in automotives, a lone red wire would be the ‘live’ cable and a lone black wire would be the ‘neutral’ cable. We’d suggest following the wires and checking where they connect at the other end so you can be certain what each cable relates to. Thanks

  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. 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 🙂

    1. We wired them into our 12V fuse board via a switch. We cut a hole in the roof the van which we attached a mushroom vent to, and then the computer fan was mounted beneath this. Hope that helps!

  6. Hi there – the link in your components list for Victron Energy MPPT 100/30 charge controller is broken… I’ve tried Amazon but there’s a vast array of them… I’m not sure what one to choose! Do you have a link please? Many thanks, Arlene

  7. Hey Climbers!
    We’re currently building our conversion (with plenty of help from your book!) and wanted to know; how do you wire the consumer unit to the inverter?


  8. Hi there. Great site BTW. You say above you added the voltage of your solar panels as voltage is added in parallel but amps stay the same. But your linked solar page says the opposite. I’m guessing from another answer that you went for the parallel option, or did you just want a controller that would allow either series or parallel? Thanks.

    1. Hi Simon, sorry for the confusion! We have made a typo above, voltage is added when solar panels are wired in series and amps stay the same. This is what we did – if you wire in parallel, on cloudy days you can struggle to get enough voltage to charge. The voltage of a single 100W panel is around 22V, so if you wire in parallel you will only have a total of 22V. On a cloudy day you may only achieve half of this, and ~14V is required to charge. Hope that makes sense!

  9. Hiya I am currently doing the wiring of my van but are coming unstuck on the midi fuse part of the wiring how do I work out what size fuses to use ??

    1. Hi Harriet, you enquired about our Nomadic Energy electrical design service but we never heard back from you – if you purchase all of your components through us, we will let you know exactly what size fuse is required for every part of your system and provide all of these, as well as explain how to install everything 🙂 if you have our book, The Van Conversion Bible, we also explain how to size fuses on page 76. Thanks!

  10. Hi Guys thanks for so much good really useful clear content. I’m just embarking on a conversion myself& the wiring is one of the most daunting aspects. I just have one quick question, I would also like to wire a 2 way switch for some lights and I noticed in your description you said it would require a 3 core plus earth cable, however when I look at the wiring diagram you have supplied, I can only see 3 cores between the two switches? It’s possible I’ve missed something really simple so apologies if thats the case! Any help greatly appreciated. Many thanks. John

    1. Hi John, the earth isn’t shown on the diagram and just needs to be connected at either end to the earth in the switch. Also just wanted to mention our new electrical system design service Nomadic Energy in case it’s of use! We can help to design your electrical system as well as provide a free wiring diagram and installation booklet, so depending where you are in the process, it may be of use 🙂 thanks!

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