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 this guide you will learn how campervan solar panel works, how to choose the right campervan solar panel kit, how to size your campervan solar system and leisure batteries, how long it will take to charge your batteries, and I will show you a campervan solar panel installation from start to finish. This information-packed guide will have solar panels on your campervan in no time! I'm Shane, I've been teaching people to convert campervans for many years, I'm the author of The Van Conversion Newsletter, the van conversion instructor at Udemy, and the proud owner of a beautiful self-build campervan called Beans. So let's jump in and have a look at solar power for van conversions!
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How long will it take the campervan solar panels to charge your batteries?
Campervan Solar Panel Installation (Illustrated Step-by-step)
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 (the wiring for campervan solar system is included in the diagram 🙂 - wiring diagram gets sent out to you straight away).
Supplies list 🛒
The anatomy of a campervan solar system
To install a campervan solar system, you need three components:
Campervan Solar panel
A solar charge controller
I am going to go into detail on each of these three components in this article; how to choose them, and how to wire them all up.
Campervan Solar Panel
How do campervan 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.
Monocrystalline vs. Polycrystalline vs. Thin Film solar panels
There are three types of campervan solar panels you can use for your campervan: monocrystalline, polycrystalline, and thin film. Monocrystalline and polycrystalline are both rigid, while thin film is flexible.
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
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 panel kit comes with an MPPT solar charge controller.
How to wire up campervan solar panels
You can wire up campervan solar panels either in series or in parallel. We will be discussing Volts, Amps, and Watts in this section, if you want a refresher on those concepts, you can check out this guide.
Wiring Solar Panels in Series
In order to wire campervan 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 (opposing sides 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.
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 single positive and negative cable runs 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.
The BIG advantage to wiring in parallel is that the panels are not inter-reliant on each other; if one of the campervan solar panels is dirty/in the shade/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 a big advantage, as in my experience I have found it very common that I am parked partially in the shade. However the advantage comes at wiring that is a pain in the butt.
If you have multiple panels on your roof, you will need a device called an MC4 connector. this device 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 like me, you will need a 4-to-1 MC4 connector!
Depending on your choice of campervan solar panels, you may also need to get inline MC4 fuses.
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 panel to the battery. It converts the powerful electricity from our solar panels into electricity our leisure batteries can use.
Let's have a refresher on the charging profiles of leisure batteries (which was discussed in this guide to leisure batteries).
Charging profiles of leisure batteries
Charging profiles of leisure batteries normally follow three stages: bulk, absorption and float. The charging limits differ between the different battery types.
Bulk: a fast, constant current charge up to ~80% State of Charge (SoC)
Absorption: much slower, constant voltage charge to reach 100% SoC
Float: a constant voltage charge which maintains 100% SoC by counteracting self-discharge
Note how different batteries charge best at different voltages. Lead-acid batteries (AGM, Gel, FLA) in particular require large voltages in the constant and current stages of the charge profile. Lithium batteries are the inverse - they require less power initially and gradually ramp up.
It is also worth pointing out that the current (amperage) works in the opposite way - at the beginning of the charge profile, the amperage starts high and gradually gets lower.
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, we could be in for a very, very dangerous time indeed. The sulphuric acid will begin to boil and the plastic casing will start to melt... 😲
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). MPPTs are a little more expensive, but accelerate solar charging of the battery up to 30% per day. On of the most popular MPPTs is the Renogy solar charge controller and bluetooth monitor.
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.
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 draw current from the campervan solar panels at the max voltage possible.
What size solar charge controller do you need?
Let's say we have four 100w Renogy solar panels wired in series. Given the 400w of solar power flowing to our 12v batteries (wired in parallel), we need to size our solar charge controller.
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 to buy a solar charge controller that is slightly bigger, for example a 40a solar charge controller.
How long will it take the campervan solar panel to charge your batteries?
If you want a recap on some of the concepts touched on here (Wh, Ah, parallel vs. series, etc.), you can check out this guide to campervan electrics.
Let's say that we have two 130Ah 12v sealed lead acid leisure batteries in our van. We wire them in parallel, giving us a total of 260Ah capacity. This equates to 3120Wh in total (12v X 260Ah). Calculating what battery size you need is discussed at length in this guide to leisure batteries.
However, because these are lead acid batteries, we can (should) only discharge them by 50%, meaning we can only use 1560Wh of power from our batteries.
How long will it take the campervan solar system to charge our leisure batteries?
Given the above information, we know we have to fill up 1560Wh of battery using 400W of solar power. So: 1560wH / 400 watts = 3.9 hours
Hang on there Obama! Solar panels typically only output 70% of the rated wattage. This is primarily due to the angle of the sun. So: 1560wH / (400W * 0.7) = 5.5 hours
That's still pretty good!
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).
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!