Over recent years I’ve noticed more of our guests are having solar panels fitted to their caravans and motorhomes. Some guests have told me its so they can go off-grid and do a spot of wild camping. Others have told me its so they can keep their leisure battery in good health during the winter months while their van is in storage.
There is a lot of information out there on solar panels. It can be hard to keep track of the best advice. So I wanted to write this post to highlight the most important solar panel information I’ve found.
We have had solar panels fitted to our home since 2012 and they have generated a significant amount of power. However, we have never got round to fitting a solar panel to our caravan. Though its something I’ve been interested in doing. Therefore, I thought I would write this post covering my own research into the various solar panels available and how to fit them. I wanted to look into what are the best solar panel types and technologies. This is going to be a pretty comprehensive post on solar panels for caravans. However, the information is also applicable to motorhomes. You can use the Table of Contents below to skip to any particular section, enjoy! 🙂
Solar Panels for Caravans Introduction
Before we start to discuss the various solar panel types and technologies I thought it would be a good idea to start with a gentle introduction into the world of solar panels for caravans. Therefore I would encourage you to watch the video below of John Wickersham at Practical Caravan. John discusses some of the important solar panels features (weight for instance) you need to consider.
Fixed Roof Mounted Solar Panels
Now, in this video, John discusses a solid framed solar panel for permanent fixing on the roof of the caravan. While this is one choice, its not the only choice as I will discuss below. There are flexible solar panels which can be permanently mounted which are significantly lighter in weight. If the idea of drilling holes into the roof of your caravan or motorhome sound terrifying there are portable solar panels you could consider.
Whatever type of solar panel you choose you’re going to need a charge controller, also known as a charge regulator. This controls and limits the voltage sent from the solar panel to your leisure battery. In full sun a solar panel can produce around 20 volts. Some leisure batteries can be significantly damaged and even a fire risk if 20 volts was supplied to it. Therefore, typically solar charge controllers limit the voltage from the solar panels to between 12-14 volts.
Portable Folding Solar Panels
The next video I would encourage you to watch is from Dan of Meet the Trudgians fame. Dan discusses his portable solar panel setup for his caravan. He discusses why he chose to go with a portable solar panel apposed to a fixed roof-mounted panel.
As Dan discusses in the video, if you want to go with a fixed roof-mounted solar panel on a caravan you need to make sure you actually have enough space. Without actually going up to the roof of your caravan you may presume there is lots of empty space. However, when you add up the single or multiple roof lights, TV ariel, heater vent etc there is not a much as space as you’d think. However, this obviously varies depending on the size of your caravan. But the point stands, before purchasing a solar panel for a permanent roof fixing you need to be sure you actually have the space to fit it.
Caravan Roof Fixed Solar Panel Leak Concerns
Dan also states he doesn’t like the idea of drilling another hole into the roof of the caravan. Now, this is a valid point, and many people don’t want another reason to get the damp tester out. However, many of the permanent kits available today and discussed below only require one the hole for the cable. The solar panel fixing kit itself is held on to the roof of the caravan or motorhome with a bonding agent. However, a hole does still need to be drilled for the power cable from the solar panel. There is a rubber cable grommet and weatherproof housing provided. But every seal does eventually fail.
Keeping Solar Panels Clean
Dan does also make another valid point about dirt and roof-mounted solar panels on a caravan or motorhome. Now, we have never since 2012 cleaned the solar panels on our roof at home. That’s partly due to the special glass surface used, but its also due to their angle. Solar panels on houses typically sit on a pitched roof. Hence, when it rains the water washes the dirt off the solar panel surface. However, on a caravan or motorhome roof, they are mounted flat, flush with the roof. Hence when it rains some dirt may be washed away, however, some dirt will likely remain.
Furthermore, as the solar panels are mounted flat against the roof of a caravan or motorhome you can only tell if they are dirty by going up there with a ladder. Now, there is no ‘dirt scale’ I can refer you to which will tell you how much solar panel efficiency you will lose for the density of dirt. But quite simply, a dirty solar panel will produce less power.
Solar Panel Technologies
I’ve briefly discussed above the initial considerations of going for either a permanently mounted solar panel on your caravan or a portable/foldable solar panel. Now, let’s look at different solar panel technologies. Starting with the difference between Polycrystalline vs Monocrystalline solar panels. Again, the quickest way to absorb a lot of this new information is via video:
Polycrystalline vs Monocrystalline Solar Panels
From reviewing the video above I quickly wanted to summarise the pros and cons of Polycrystalline and Monocrystalline solar panels.
- Polycrystalline Solar Panels
- The solar cells are square edged with a blue appearance
- – Less efficient than monocrystalline solar panels (15.5%)
- + Slightly cheaper than monocrystalline solar panels
- – Slightly less efficient at warmer temperatures than monocrystalline solar panels
- Monocrystalline Solar Panels
- Have an almost black appearance with rounded solar cells
- + More efficient than polycrystalline solar panels (17.5%)
- – Slightly more expensive than polycrystalline solar panels
- + Slightly more efficient at warmer temperatures than polycrystalline solar panels
The reality either poly or monocrystalline solar panels for your caravan or motorhome are a valid choice. With the small size of solar panels either fixed or portable, the differences between the two technologies are negligible.
Rigid or Flexible Solar Panels?
Typically when most people think of solar panels for caravans they think of the aluminium Ridgid frame solar panels. A couple of our guests do have flexible solar panels and they do seem to be growing in popularity. Its pretty easy to see why when it comes to caravans and motorhomes. In either a permanent roof installation or a portable foldable solar setup, a flexible panel is lighter and take up less space. However, there are some apparent downsides to flexible solar panels which you should be aware of before making a purchase.
Issue 1: Flexible Solar Panels and Heat
For a flexible solar panel bonded to the roof of your caravan or motorhome heat may be a potential problem. In our UK climate, the panel will probably not melt as seen in the video above. However, solar panel power efficiency will be affected. While I’ve personally not used a flexible solar panel, I can personally testify that heat plays a big role in how a solar panel performs. The solar panels on our home perform much better on a sunny/windy day than a sunny/calm day. When the wind passes under the solar panel it keeps them cooler and they noticeably produce more power.
If you’re using a portable flexible solar panel they will not be trapped against a surface. Therefore they will be better ventilated. However, as the video above shows, there are other potential downsides to flexible solar panels.
Issue 2: How Flexible is Flexible?
With this issue, its along the same line of questioning as ‘how long is a length of string?’. The point being, while they may be called ‘flexible’ solar panels, they have their limits and will crack and fail if pushed past their limits. It’s a bit like when you’re at school and you play with the ‘bendy’ ruler. You go ‘oh wow, look at much it can bend!’ before it ultimately snaps. The point being, don’t presume you can handle a flexible solar panel with any less care than a rigid panel. In fact, according to Will in the YouTube video above (who’s off-grid videos are excellent by the way), flexible solar panels are often not built to a great quality, which leads us to the final issue.
Issue 3: Flexible Solar Panel Warranties and Durability
For any fixed solar power setup for a caravan or motorhome of 100-200W, you’re going to be spending a couple of hundred pounds at least. Therefore, product warranties and durability are a consideration. Not only that, you want to be able to depend on this solar setup so its working when you need it. There appears to be literally hundreds of flexible solar panel manufacturers out there. That’s not actually the case, there are probably ten to twenty manufacturers. The rest are various different companies rebranding the solar panels.
In either case, don’t put too much weight into a claimed ’25 year guarantee’ by some of these companies. It means zero if they’re not around to back it up. Really, when it comes to making your choice its going to likely be made on reviews. Its not impossible for a ridge solar panel to fail. It just appears to be less likely than a flexible solar panel failing.
Solar Charge Controllers are Essential
Ok, so no matter what size/type of solar panel you choose, you must use a solar charge controller. Without the charge controller, the solar panel will send out an unregulated voltage to your leisure battery, potentially up to 20V. That’s bad for your battery and potentially dangerous, so you need a solar charge controller.
Many of the solar panel kits you can buy online come with a solar charge controller. However, just as different solar panels are made to different standards, the same goes for charge controllers. Therefore, you may want to consider making a separate panel and charge controller purchase. Will who produced the video above on the ‘Truth About Flexible Solar Panels’ has also done a very detailed video on solar charge controllers. Pre-warning, this video is 20 minutes long.
Cheap solar charge controllers lack battery temperature management
As Will references, some solar charge controllers cannot monitor battery temperature. For lead-acid batteries in particular (most leisure batteries are lead-acid) this can lead to issues.
Many of the solar panel kits online come with the cheap blue solar charge controller. That cheap solar charge controller has no battery temp monitoring. You may want to consider spending a bit more for a solar charge controller with a battery temperature sensor.
What Size of Solar Panel do you Need?
So you know that you want a solar panel. But before you can purchase any products you need to size the setup to meet your needs. If the aim of the solar panel is just to trickle charge your leisure battery during the winter months, a single small panel between 50W and 100W could do the trick. However, if you are interested in going wild camping off-grid, you’re probably going to need a larger solar panel.
The video below from Matt at Exploring Alternatives YouTube channel is worth a watch. Matt goes through how he calculated the size of the solar setup he needed for his campervan. He added up the power requirements of all the equipment he wanted to power. He then used an online calculator (details below) to size the solar panels required to meet that demand.
Solar Power Calculator
As Matt discusses in his video, first he added up the total power requirements for all his devices. Then he decided he wanted to be able to run the devices for 8 hours a day. The calculator over at the Renogy website requests the average sun-hours which is an important part of the calculation. Therefore, you need to consider there are fewer sunlight hours in winter (at a lower intensity) than the summer. If you do intend to go wild camping in the winter months, a significantly larger solar setup would be required.
Renogy also has a calculator for cable gauge which you could use for the solar panel setup in your caravan or motorhome. The further distance between the solar panel and charge controller the larger cable gauge required. In the video above, Matt also discusses inverters. You can check out my previous post on caravan inverters for more examples. Put simply, if you want to run your 230V devices from your solar panel and 12V leisure battery setup, you’re going to need an inverter of a suitable size. With a suitably sized inverter, you could run a microwave, kettle or TV.
Fixed/Rigid Solar Panel Installation Video
One of the best solar installation videos I’ve come across is from MMM TV. While they obviously focus on motorhomes the solar panel installation video below is just as applicable to caravans. Its generally an excellent video on the installation process, but I do have a few comments below.
Solar Panel Roof Fixing Brackets
This video is one of the best on how to fix a solar panel to the roof of a motorhome or caravan. However, there is a missed step. The feet which hold the solar panel to the roof do not require screws or bolts, a bonding agent is used. Now, I’m quite happy using bonding agents, there are some excellent products out there. However, every bonding product clearly states ‘thoroughly clean the surface’. That step appears to be have been skipped in the video above. As a result, the bonding adhesion to the caravan or motorhome roof surface could fail. As a result, driving down the road one day you hit a pothole. The wind then catches the solar panels and its bye-bye. Or, its stays attached via the power cable and repeatedly smashes into the roof or your caravan or motorhome.
So if you are going to use a bonding agent to secure a solar panel to the roof of your caravan or motorhome thoroughly clean the surface. You’re going to want to use a degreasing agent, something like methylated spirit. Essentially, thoroughly read the surface cleaning requirements stated on the bonding tube.
Flexible Solar Panel Fixing Video
A permanent solar panel on your caravan or motorhome means either a rigid aluminium or flexible product. As can be seen in the video above, aluminium panels are typically fixed to the roof with four brackets. But what about flexible solar panels, how are they fixed to the roof of a caravan or motorhome? Well, typically most people will use some form of adhesive tape, in the video example below, Eternobond is used.
While a flexible solar panel can be fixed to the roof of a caravan or motorhome with an adhesive tape product, there are potential issues. In the video above, rain tracked under the tape and under the flexible solar panel. As long as there are no holes in the roof under the solar panel it may not be an issue. However, more moisture will get under the solar panel. As it expands/contract depending on temperature, eventually the bond of the adhesive tape will fail. Therefore, I’m going to do some more research on the best flexible solar panel fixing methods.
Conclusions on Solar Panels for Caravans and Motorhomes
When it comes to choosing a solar panel setup for a caravan or motorhome there is lots to think about. I’ve not had a chance to continue my research to reference any particular solar panels that particularly interest me. But I hope to keep updating this post over time.
I hope you found the above information on solar panel setups for caravans and motorhomes interesting. I also hope you consider coming to visit us here at Horton Common at some point in the future. 🙂