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The Complete Guide to Campervan Solar Systems

Did you know that the amount of sunlight that strikes the earth's surface in an hour and a half is enough to handle the entire world's energy consumption for a full year! Solar power for van conversions is totally essential. In the Roaming Home 2023 study we found that 78% of people install a campervan solar system.

In this we will learn how solar panels work and how to choose the right solar panel kit. We will also look at campervan solar panel installation.

I'm Shane, I've been teaching people to convert campervans for years; I'm the author of Roaming Home; The Comprehensive Guide for Converting Your Van Into a Campervan, writer of The Van Conversion Newsletter, instructor of The Van Conversion Course over at Udemy. And full-time vanlifer for 4 years!

Now let's jump in and have a look at campervan solar setups!

Index

 

Note: Before we hop in, you will definitely want to grab yourself a wiring diagram which you can get for free by signing up to The Van Conversion Newsletter


This post contains affiliate links, which means that if you click a product link and buy anything from the merchant (Amazon, eBay, etc.) we will receive a commission fee. The price you pay remains the same, affiliate link or not. By using these links, you are helping me to continue writing free educational content!

 
campervan electrics book

Supplies list 🛒

Bluetooth monitor

​Bluetooth monitor

Monitor your Renogy solar charge controller with your phone


Adhesive cable clips

Adhesive cable clips

Securing the solar cables on the roof


10awg solar panel cable

10AWG solar cable

Connecting solar panels & solar charge controller


Solar cable entry

Solar cable entry

Passing solar cables through the roof


40a inline breaker

40a inline breaker

Protect the Solar Charge Controller from surge


40a inline breaker

50a inline breaker

Protect the rest of the electrical system from surge

Isolator switch

​Isolator switch

Leisure battery kill switch


200a ANL fuse

​200a ANL fuse

Protects the leisure battery in case of surge

Leisure battery terminal connector

Leisure battery terminal connector

For connecting cable to your leisure battery


250a bus bar

​2X 300a heavy duty bus bars

Common connection point for positive and negative cables

Leisure battery

12v fuse box

​12v fuse box

To protect all your 12v appliances

Heavy duty lugs

​Heavy duty lugs

For connecting cables to the bus bars

Victron battery montior

​Victron battery monitor

For monitoring the levels of your batteries


The anatomy of a campervan solar system


To install a campervan solar system, you need three components:

  1. Solar panel(s)

  2. A solar charge controller

  3. Leisure batteries

How do solar panels work?

Photovoltaic panels (PV), also known as solar panels convert energy from the sun (photons) into electricity which you can use to power your campervan.

When the sun shines onto a panel, the energy is absorbed by the PV cells. The photons knock electrons free from atoms, generating a flow of electricity.

The solar cells form an electrical circuit in the panel, thus allowing the flow of electrons through the circuit, creating electricity.

What size solar panels for a campervan?

In the Roaming Home 2023 study, we found that most people install a 300W campervan solar setup, followed closely by a 400W solar system. Though the results were quite distributed.

What size solar should I install on my campervan?

Monocrystalline vs Polycrystalline vs. Thin film solar panels


There are three types of solar panels you can use for your campervan:

  • Monocrystalline

  • Polycrystalline

  • Thin film

Monocrystalline and polycrystalline are both rigid, while thin film is flexible.

Thin film vs monocrystalline vs polycrystalline solar panels for van conversions

Monocrystalline solar panels

Pros: Most efficient campervan solar panel, long life, long warranty (20 years on average)

Cons: Heavier, bulkier, don't bend, less rugged

Polycrystalline solar panels

Pros: long life, long warranty (20 years on average), cheaper than monocrystalline

Cons: Heavier, bulkier, don't bend, less rugged, not as efficient as monocrystalline

Flexible solar panels (thin film)

Pros: Very light, super-slim (stealthy), bendy, more rugged

Cons: Less efficient, shorter warranty (5 years on average)

Campervan Solar Panel Kit

The most popular campervan solar panel kit comes from Renogy. They supply either 2X 100w monocrystalline campervan solar panel kit OR a 4X 100w monocrystalline campervan solar panel kit . Each campervan solar setup comes with an MPPT solar charge controller.

Campervan Solar Panel Kit

Campervan solar panel wiring diagram

You can wire up campervan solar panels either in series or in parallel.

Wiring solar panels in series

In order to wire solar panels in series, we daisy chain them together. The positive from one panel runs into the negative of the next panel. We then run the last remaining positive and negative cables (on each end of the system) down to our solar charge controller.

When we wire campervan solar panels in series, the amperage (current) remains the same, but both the voltage and wattage increase. For example, Each solar panel in the diagram below is a Renogy 100W monocrystalline panel. Each panel has a max voltage of 18.6V, giving us a max of 5.38A per panel. When we wire the four campervan solar panels in series, the voltage increases to 74.4V and the wattage increases to 400W.

How to wire solar panels in series

In a nutshell, when we wire campervan solar panels (or any device) in series, they act as a single unit - like one huge solar panel.

Advantages Of wiring solar panels in series:

  • Can use smaller wire size due to lower current

  • Wiring is more simple, requiring less connectors and equipment

  • Normally output higher power

  • Distance is less important to efficiency

Wiring solar panels in parallel

In order to wire solar panels in parallel, we connect all the positives together and all the negatives together. The combined positive and negative cables run down to our solar charge controller.

When we wire campervan solar panels in parallel, the voltage remains the same, but both the amperage and wattage increase. For example, Each solar panel in the diagram below is a Renogy 100W monocrystalline panel. Each panel has a max voltage of 18.6V, giving us a max of 5.38A per panel. When we wire the four solar panels in series, the voltage remains at 18.6V but amperage increases to 21.52A and the wattage increases to 400W.

How to wire solar panels in parallel

The BIG advantage to wiring in parallel is that the panels are not inter-reliant on each other; if one of the solar panels is dirty or in the shade or broken, the others are not affected. In contrast, when wiring in series, if you are parked partially under the shade, your campervan solar system efficiency will be greatly reduced.

This is an important advantage, as in my experience I have found it very common that I am parked partially in the shade.

However this advantage comes with more technical wiring and the necessity to use thicker cabling.

To connect parallel solar panels together, we have two options: MC4 connectors or a combiner box.

van conversion diagram pack

MC4 connectors

One method of connecting multiple panels on your roof is to use a device called an MC4 connector. An MC4 connector routes many wires into one. If you have 2 panels, you will need a 2-to-1 MC4 connector, or if you have 4 panels, you will need a 4-to-1 MC4 connector.


How to wire MC4 connectors

Combiner box

Another way to marry the solar cables together is to use a solar combiner box, a consumer unit specifically for solar panels. This both combines and fuses (breaks) the solar cables.

A combiner box is generally only needed in larger systems with a lot of solar panels. Van conversions can generally do with just a set of MC4 connectors.

How to wire a solar combiner box

Optimal solar panel angle

The ideal angle for a solar panel installation is equal to the latitude you are currently residing. If your panels are perpendicular to the sun, and pointing directly at it, you will have a big increase in efficiency.

Renogy sell excellent solar panel tilting kits. Or if you felt up to the task, you could build your own instead!

4waysolar.com
Optimal solar panel tilt

For this reason, it is quite common (and extremely useful) to install a tilting solar panel rack on a campervan.

Hench tilting solar panels by @vandmvanlife
Hench tilting solar panels by @vandmvanlife

Solar panel fusing

It is essential that we add a circuit breaker between the solar panels and the solar charge controller. Specifically, we must install a double pole DC MCB; 32A is generally used, though you should do your own sizing. The MCB should have a minimum rating of 250V. It can be installed on a DIN rail inside a small garage consumer unit. A solar-specific MCB like the one shown below can easily be purchased online.

32A DC double pole MCB inside a mini consumer unit
32A DC double pole MCB inside a mini consumer unit

We must use an MCB for two reasons:

  1. Inline breakers (like those from BlueSea or Eaton-Bussmann) are generally rated up to 48V max. This may cause problems if you are wiring your panels in series, where the voltage increases as panels are added.

  2. Inline breakers do not satisfy the “Must disconnect both the positive and negative wire” requirement set by NEC 2020 Article 690.13 section (E).


Solar charge controllers

A solar charge controller is a device which keeps our leisure batteries from overcharging by regulating the voltage and current coming from the campervan solar panels. It converts the powerful electricity from our solar panels into electricity our leisure batteries can use.

A solar charge controller ensures that the voltage and amperage matches the expecting charge stage of the battery. It is paramount that it does its job correctly. For example, if we had a campervan solar panel installation with four panels wired in series (74.4V) wired directly to our leisure batteries, the sulphuric acid would begin to boil and we could be in for a very, very dangerous time indeed.


What is the difference between a PWM and a MPPT solar charge controller?

There are two types of solar charge controllers: MPPTs (Maximum Power Point Tracking) and PWMs (Pulse Width Modulation).

PWMs

A PWM is a relatively simple device that is essentially a smart switch. It pulsates on and off, recognising when it needs to send power to the batteries (per the charge profile). It is about half the price of an MPPT, but about 30% less efficient per day (big difference!).

PWMs draw current from the campervan solar system just above the voltage of your leisure batteries.

MPPT

A MPPT is a solar charge controller which digitally tracks the charge profile of the leisure batteries in order to be as precise as possible with its energy delivery. They are a lot more efficient than PWMs

MPPTs are a little more expensive, but accelerate solar charging of the battery up to 30% per day. MPPTs are slowly but surely taking over from PWMs entirely.

MPPTs draw current from the campervan solar panels at the max voltage possible.


renogy

What size solar charge controller do you need?

Let's say we have four 100W solar panels wired in series flowing to our 12V batteries.

We must figure out how many amps at 12V our solar panel set will actually produce. We can see that our solar charge controller must be able to handle 400W ÷ 12V = 33.7A. So we should buy a solar charge controller that is slightly bigger, for example a 40A solar charge controller.

Campervan solar panel installation (Step-by-step)

In this step by step guide, I will be showing you how to install solar panels on the roof of your campervan. First we will look at how to install flexible (thin film) solar panels, then we will look at how to install rigid mono/polycrystalline solar panels. I have flexible solar panels on my campervan because they are more discreet than solid.


Note: Before we hop in, go grab yourself a wiring diagram which you can get for free by signing up to The Van Conversion Newsletter (the wiring for the campervan solar system is included in the diagram 🙂 - wiring diagram gets sent out to you straight away).


How to install flexible solar panels on a campervan



Step #1: Clean the roof

Not much to say here... Get up on your van roof with some warm soapy water and get to work!

Step #2: Remove rust from the top of the campervan

Whether or not you're installing solar panels on your campervan, removing rust is always a good thing! If you need a refresher on how to do this, read this guide on how to remove from from a van.

Remove rust from roof of campervan

Step #3: Stick strips of 3M VHB (Very High Bondage) tape on the van

Place strips of the double-sided 3M VHB tape on the roof of your van. This stuff alone will stick the campervan solar panels down for life.

Strips of VHB tape to connect solar panels to roof

Step #4: Stick the flexible solar panels onto the roof of the campervan

Carefully place the flexible solar panels on top of the 3M VHB strips and gently press them down.

Solar panel temperature: Cooler solar panels are more efficient. Flexible solar panels can get quite hot if there is no air gap underneath them. Luckily on the Ford Transit, there are ridges that run down the length of the van, providing an air gap of about an inch, through which air can flow. If your van does not have ridges, you can still install flexible panels, though they might not be as efficient. Alternatively, you could raise the panels up using metal risers.

Air tightness: Some people use high bondage glue (like sikaflex) instead of VHB tape. This is fine too. However, if you are using glue, make sure you pour it in strips, just like the VHB tape. DO NOT make an airtight seal with the glue - water can get trapped in there, expand, and do damage to the panels. It will also reduce the efficiency of the panels due to higher heat.

Stick solar panels to roof of van

Some people choose to secure the panels to their van even more by using well nuts in each of the four corners of each solar panel. A well nut is like a rivnut / plusnut; it is used to fasten something to a surface and to seal the bolt hole. As the bolt is screwed in, the well nut expands on the inside, thus locking it in place.

I can tell you that after years of living in my van full-time, using only VHB tape, I have never had a single problem with my solar panels coming loose. In my opinion, nuts are not really needed.

well nut for attaching solar panel to van conversion

How to secure solar panels with well nuts:

  1. Drill a hole through the van to match the corner of the solar panel. The hole size should match the size of the well nut (M8 - M10 preferable for a solar panel)

  2. Place the well nut through the panel and into the hole

  3. Screw an appropriate bolt into the well nut and the well nut will gradually expand and seal the hole.

  4. For extra waterproofing, I would highly recommend using some sealant on top of the well nut to be super-duper sure you won't get a leak.

Step #5: Stick down loose wiring on the roof using adhesive cable clips

Next, we want to get all that messy wiring out of the way and make it look nice! Use cable ties to bunch everything together and stick it to the roof with adhesive cable clips. I would advise using the 3M VHB tape to stick the cables down.

Step #6: Wire up the campervan solar panels and bring the cables inside the van

Wire up the campervan solar panels either in series or parallel, as discussed before. Most people use 10 mm² solar cable for this job.

how to wire flexible solar panels

Then bring the positive and negative wires inside the van. The wires enter into the van through a solar cable entry gland. You can learn how to install the solar cable entry gland in this guide.

Solar cable entry gland

Step #7: Add an MCB to the solar wiring before the solar charge controller

Add an appropriately sized DC double-pole MCB to the positive wire running to your solar charge controller. I used a 40A inline breaker (because I can expect 33.3A maximum to be delivered). We want to place the breaker as close to the panels as we can get it (to protect as much of the wire as we can).

solar breaker installation

SAFETY NOTE: DO NOT HOOK THE SOLAR CHARGE CONTROLLER TO THE SOLAR PANELS UNTIL THE LEISURE BATTERIES ARE CONNECTED.

It can fry your solar charge controller. Beware.

Step #8: Connect the solar charge controller to your bus bars

The next part of the solar panel installation is to wire the solar charge controller to your positive and negative bus bars. The bus bars run down to your batteries. We add a 50A inline breaker (Bluesea or Bussmann only) to the positive line running to the bus bars. I used two 300A heavy duty bus bars and 10 mm² cable.

Heavy duty bus bars
Heavy duty bus bars

Note: All cable that runs into the solar charge controller should be connected with ferrules to ensure a solid and safe connection.

Bus bar to mppt

The wire from the solar charge controller is connected to the bus bar using a large lug.

Large lug connector
Large lug connector

Step #9: Connect your 12V fuse box to your solar charge controller

Last step! Connect your 12V fuse box to your solar charge controller.

12V fuse box
12V fuse box

This will send power to all your 12V appliances (fan, heater, lights, etc.). I used 10 mm² cable in my van build and added a 40A breaker onto the positive wire (as close as possible to the solar charge controller).

MPPT to fuse box

Connecting the fuse box to your MPPT is technically optional. You could run the fuse box directly from the bus bars. However there are two benefits of running the fuse box from the MPPT:

  • You can power your appliances directly from the solar panels when the sun is out (rather than running through your leisure batteries)

  • You get a bunch of cool monitoring capabilities on the MPPT

Most people will also wire up a 12V switch board after the fuse box before running the wiring out to the individual appliances. This allows you to turn individual appliances on and off. In my opinion it’s a must! We will look at how to wire one in a later chapter.

12V switch panel
12V switch panel

Step #10: Ground it

Many solar charge controllers do not need independent grounding - it is enough that the common negative bus bar in the system is grounded. It is best to check the manufacturer’s guidelines for more information on your model. For instance, only the 20A Victron MPPT needs grounding.

van life academy

How to mount rigid campervan solar panels

First go grab yourself a campervan solar panel kit, like this awesome 400w kit from Renogy.

  1. First attach metal brackets to the campervan solar panels. The Renogy campervan solar panel kit comes with a Z-bracket mounting system, which allows an Inch of room underneath for airflow to increase the efficiency of the panels.

  2. Bring the bracket-mounted solar panels up onto the roof of your van and mark with a pen where you need to drill into the van.

  3. Drill into the spots you have marked on the roof with a drill bit appropriate to the size of your bolt.

  4. Bolt the campervan solar panels into the roof (place the bolt into the hole from above, and screw the nut on from inside the van).

Note: To get a waterproof seal, I would advise applying a good amount of sealant around the hole you have drilled before tightening down the bolt. Alternatively, you could add a small piece of mastic / butyl tape over the hole. Some people choose to use Loctite Marine Adhesive instead. All three of these options will work.


Here is a great video on how to install rigid solar panels on a campervan.


Conclusion

And there we have it! What an adventure that was... I truly hope you found this article to campervan solar panel installation useful!


Don't forget to subscribe to The Van Conversion Newsletter for everything you need to get started with your own van conversion (I'll send you a free wiring diagram when you join).


If you're looking for some guidance with your van conversion, you might be interested in Roaming Home; The Comprehensive Guide for Converting Your Van Into a Campervan. In the 380-page book (or ebook), you'll learn directly from me how to convert a van into your dream home - no prior experience needed!

campervan book

Until next time,


Shane ✌️


1 Comment


terryfinn0
Oct 06, 2023

What a superbly written tutorial.

Many Thanks,

Terry in Dublin.

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