For any motorhome owner who cares about the environment, it can be disconcerting that these big, heavy vehicles we love to use to enjoy nature… run on those nasty fossil fuels which jeopardise a future where we continue to enjoy it.
Luckily, if you want to decrease your use of fossil fuels on the road, you can do so considerably by installing solar panels in your motorhome.
In short, installing a system for solar panels in your campervan means you’ll be able to harness the sun’s power and store it in your leisure battery, so that it provides the energy for the gadgets and appliances you use on the road. In this blog, we will walk you through all the different components of a solar energy system, how to choose and install them, and how to maintain the system for optimum energy efficiency.
What Components Make up a Motorhome Solar Power System?
1. Solar Panel: These generate electricity by turning particles of sunlight into energy. It all sounds pretty magical, and you don’t have to know the exact process by which this works. But, in case you’re interested, they contain cells of semiconductive material, usually silicon, which are set in a metallic frame and tempered glass. When subject to sunlight, these photovoltaic cells create a flow of electric charge inside the solar panel due to the photoelectric effect.
2. Wiring: this flow of electricity travels in a circuit of wires that connect groups of solar panels, called ‘arrays’. The primary purpose of the ‘arrays,’ is to enable the transfer of electricity created from the solar panel to your battery and devices. To connect a cable to a solar panel correctly, use an MC-4 connection terminal.
3. Charge Controller: The solar charge controller regulates the incoming voltage/current from your solar panels. In a campervan this is crucial; when you’re on the move, the amount of power you generate from your solar panels will fluctuate a lot. The charge controller (or sometimes called the charge regulator) helps prevent any potential issues from a fluctuating power input that may damage your solar charge system. Without it, if you connect your solar array straight to the battery bank, you could damage your batteries and reduce their lifespan, or end up with a vehicle fire. Batteries have a specified voltage capacity which, if exceeded, exposes it to numerous overcharges and over discharges.
4. Leisure Battery: The primary purpose of a leisure battery is to efficiently store electricity created by a solar power system, so that it can be used to power appliances and gadgets in your van later on.
5. Inverter: You might need to add an inverter into the campervan solar set up. The power drawn from your solar panels, used by your batteries, will most likely be a 12V DC current. An inverter like this one will change this to a 120V AC current, so that things like a fridge, TV, heater, or microwave can use it. If you have a more simple array of appliances for weekend trips in your camper, don’t worry about this step.
When to install solar panels
It’s best to start the electrical part of your installation early, and the solar panel system is part of this process. Well thought-out plans are key to avoiding extra work and maintaining easy access during the build. Preferably, make a start before laying floors or insulation. Lay cables before installing the components, ready for connecting at the right time in your build. Be sure to leave enough extra cable just in case, and number or tag every end of every cable so you remember what each is, later on. Also, components like the fuse blocks, bus bars and switch panels (which we will come back to) early on.
Choosing your solar panels
Before you buy brand new solar panels, be sure to do the measuring and make sure they’ll actually fit on top of your campervan. This may sound obvious but it’s a common error that many people make. Once you’ve done this, you have a couple of choices for your solar panel types; Monocrystalline or Polycrystalline Solar Panels. There is no clear answer as to which makes the best solar panels for a van conversion, but luckily, it’s not too hard to choose between them. This decision will be determined by your budget and the amount of space you have on top of your motorhome.
Monocrystalline Solar Panels
- These solar panels have solar cells made from a single crystal of silicon.
- These panels are slightly more efficient compared to a Polycrystalline solar panel.
- They require less floor space to produce an equivalent power output.
- The surface generally has a black hue.
- These panels tend to be more expensive compared to Polycrystalline.
Polycrystalline Solar Panels
- These solar panels have solar cells made from many silicon fragments, which are then melted together.
- These panels are slightly less efficient compared to Monocrystalline solar panels.
- The floor space required for Polycrystalline solar panels is usually more, compared to a Monocrystalline solar panel, to produce the equivalent power output.
- The surface generally has a blue hue.
- These panels are generally less expensive compared to Monocrystalline.
Luckily, technology is developing at a rapid pace. It’s easy to find ideal solar panels for campers, which are high quality and not only lightweight and durable, but also flexible so that they easily fit to the topography of your van!
Designing your array
Firstly, you can either wire your solar panels in a series or in parallel. Wiring in a series allows all the solar panels to act as one entire unit. This is done by connecting the positive terminal of the first solar panel to the negative terminal of the next one. Connecting them like this increases the total voltage generated from the solar array whilst the amperage stays the same. This puts out more power under normal circumstances, requires less wiring, and makes the distance from the solar panel to the charge controller less critical.
Alternatively, wiring in parallel means that each solar panel acts as an independent unit. This is done by connecting all positive terminals of all the solar panels together, and all the negative terminals of all the panels together. This increases the total amps generated from the array, whilst the voltage stays the same. The advantage of this is that the system performs better when one of the solar panels is dirty, falling in the shade, or if it gets broken.
As mentioned above, you’ll need to connect solar panels together via a watertight connection plug called an MC4 Connector. Although some installers simply cut and join their wires using more traditional ways (crimping and soldering), if you’re not familiar with electrical installations, an MC4 connector will make everything easier and safer.
For the actual installation, you can make life easier for yourself by purchasing a solar panel mounting kit like this one from the Renogy Store on Amazon.
Choosing your controller
There are two types of charge controllers. The are Pulse Width Modulation (P.W.M.) charge controllers, and Maximum Power Point Tracking (M.P.P.T.) charge controllers
The P.W.M. controller is the more basic of the two controllers. They match the solar array voltage to the voltage required to charge the batteries. This one works by simply turning on and off, hence the name, pulse rate modulation. When on, it sends power to the batteries. When off, it monitors the capacity of the batteries, making sure to properly charge the batteries throughout the full state of charge. A P.W.M. controller is around 10% – 40% less efficient when compared to an M.P.P.T. controller. It can also cause interference to the on-board radio equipment, due to the sharp pulses generated for the battery bank charging. As such, this type of controller tends to be around half price or less.
The M.P.P.T. Charge Controller has the added functionality of electronically tracking and delivering the most optimal amount of power coming from the solar array to the battery bank. If the output voltage of the solar array (24V, 48V or more) is higher than the battery bank voltage (usually 12v), the controller will bring the power down to the optimal charge voltage (generally between 13.8V and 15V). The controller will also compensate for the ‘drop’ by increasing the current. As with the P.W.M. controller, the M.P.P.T. charge controller can monitor the capacity of the batteries, and match the necessary voltage required to charge those batteries. Another benefit of M.P.P.T. controllers is a reduction of the wire size (gauge) needed when connecting a solar array that is connected in series. This is due to the higher voltage/lower current coming from the solar array. So, M.P.P.T. controllers are around 10% – 40% more efficient when compared to a P.W.M. controller. However, they tend to be around twice the price or more (depending on technology/make).
Your budget will be the main decider for which controller type you go for!
There are some bits and pieces that will seriously make your life easier when it comes to installing the solar panels to your campervan’s electrical system. Because this system, in combination with all the other electrics, can have upwards of 20 circuits, each needing a dedicated fuse, its preferable to have all these fuses located together for easy maintenance. Fuse boxes hold multiple fuses attached to their circuits all in one place.
And, rather than attaching each circuit directly to the battery, install a bus bar to the battery, again making maintenance, installation and future expansion of your system easier. To decide on fuse boxes and bus bars, count your circuits and add up the total current of every circuit you plan to connect (just assume everything will be switched on at the same time). The fuse block and bus bars need to be able handle a current greater than your total, and you’ll need more fuse holders and terminal connecting points than you have circuits. As they aren’t cheap, oversize these components to allow for future expansion. You can also buy a combined fuse block and bus bar for easier installation.
Similarly, switch panels keep things tidy when there are few switches for the various appliances powered by solar panels for campers.
The complete system layout
Most DIY conversion blogs feature diagrams which, in simple terms, show how the solar panels in your motorhome’s electrical system can be laid out. Check out the wiring diagram by VanLifeAdventure, which is one of the clearest out there.
For a better idea of the other components in the electrical system and how to install them, read our recent blog about setting up motorhome electrics. We’ve got detailed sections on how to choose the best inverters and leisure batteries for your system. Battery installation is also easier in the tight spaces of a motorhome if you buy quick-release terminal connectors like these from Motopower.
Electrical Regulations for Motorhomes
Campervan electrical regulations vary from country to country. Some places may have mandatory regulations, and you may experience restrictions on use unless they’re adhered to. In other places, only guidelines are issued. If possible, have a professional check over your DIY system, if only for peace of mind that it’s safe and follows best practice. In the UK, check guidelines on the British Standards with the Caravan Club.
Tips for getting the most from your solar power system
- When trying to capture solar energy, make sure you’re parked so that as much of your panels are in direct sunlight as possible. Even small shadows can affect the amount of power generated by solar panels for campers. Midday sunlight is the strongest, as it is the most direct.
- Do regular leisure battery maintenance. A poorly maintained battery will affect how well your solar panels effectively charge them back to the optimal capacity.
- Replace electrical items inside your campervan with the equivalent energy-efficient ones. Think halogen bulbs to LEDs. By doing so, you can drastically reduce the power you consume, meaning your solar panels won’t have to work as hard.
- Pollution, dust, fallen leaves and pollen from trees, and bird poop can all reduce the amount of sunlight hitting the solar panels on your motorhome. If you regularly clean your solar panels with soap and warm water, you’ll remove any build-up of dirt which should keep your panels efficient.
Other tips for decreasing fossil fuel use
- Have your wheel alignment checked if the wheels aren’t running straight and true, their tyres will be scrubbing which consumes unnecessary power and fuel.
- Make sure your vehicle is regularly serviced, preferably annually.
- If you often travel in dusty conditions, have the air filter changed more frequently. A blocked filter restricts the amount of air going into the engine, which will make it run inefficiently and consume more fuel.
- Drive mindfully; accelerate smoothly to your chosen cruising speed – planting the gas pedal to the floor and racing through the gears uses lots more fuel. So, keep your cruising speed steady and reasonable.
- Check your tyre pressures – soft tyres consume energy, which in turn, uses more fuel.
- Unfortunately, solar panels themselves are energy intensive to make and can leave behind some pretty environmentally toxic waste material once you’re finished using them. So, if you really want to do an eco-friendly conversion, consider buying (or even making your own!) solar panels from reclaimed and recycled photovoltaic material.
Hopefully, this blog has given you a better idea of how to best fit solar panels for your van conversion.