Fitting a Solar Panel

Fitting a Solar Panel to a Caravan or Motorhome for free energy!

For this article I thought I would show what’s involved in fitting a solar panel to a caravan or motorhome as they are essentially the same electrically wise.

Having a solar panel fitted gives you more freedom when camping as it allows you to be “off grid” for longer, this opens up more places to visit and be a bit eco friendly as well! If you prefer your 240v comforts you could always fit an inverter which takes 12volts DC (battery power) and then turns it into 240V AC. 

Last update on 2023-01-03 / Affiliate links / Images from Amazon Product Advertising API

Last update on 2023-01-03 / Affiliate links / Images from Amazon Product Advertising API

Last update on 2023-01-03 / Affiliate links / Images from Amazon Product Advertising API

As with most things there are different types of solar panels available, different outputs (expressed in watts), different sizes even flexible ones. 

I have written an article all about the various types of solar panel and how to calculate what size you would need etc… it can be found by clicking these blue words.


Tools required for fitting a solar panel are pretty basic really :

Solar Panel Kits

Most people fitting a solar panel will buy it as a “kit” which will include the basics to get started.

You will need to buy extra cable to run from the controller to your batteries, fuse holders and fuses and also the adhesive sealant which is how we attach the solar panel to the caravan or motorhome roof! There are no screws needed for this as the modern polymer sealants adhere much stronger than screws ever would, this old method just creates holes that will eventually leak at some point too!

Included in this kit I’m fitting is a solar panel, end spoilers or deflectors (not all panels come with these), some cable, a gland to allow the cable to pass through the roof, controller (voltage regulator) and instructions. I used Soudals Fix All Turbo on this installation to bond it to the roof or you could use Dekasyl MS-5  or equivalent.

Last update on 2023-01-03 / Affiliate links / Images from Amazon Product Advertising API

Last update on 2023-01-03 / Affiliate links / Images from Amazon Product Advertising API

Fitting the solar panel to the roof

First off lay everything out and make sure everything is there. Check that the solar panel frame and the spoilers have not been dented or bent in transit.

fitting a solar panel to a caravan

Next, attach the end spoilers or deflectors to the ends of the panel. They normally are held in place by a couple of screws but I always run a bead of the adhesive sealant down the connecting face so that it effectively bonds it to the panel then fit the end caps.

fitting motorhome solar panel
fitting as solar panel caravan

Worth mentioning is that the spoilers are designed to help the air flow over the solar panel and not under it and potentially losing it on a motorway. So the idea is that the panel gets fitted with the narrow end with the spoiler facing the direction of travel.

I’ve never known a panel to come off in all honesty but if fitting a super large panel it may be worth bearing in mind!

Lift the solar panel up on to your caravan or motorhome roof and lay it on some of the packaging cardboard.  Hopefully you have looked on the roof before hand and had a little measure up to make sure the solar panel will fit! 

  • Remember that if the roof is made from aluminium (as oppose to fibreglass) you will need to stand/kneel on thick cardboard or something that spreads your weight as the roof will dent quite easily.
  • Panel vans roofs dent easily too even though they are castellated they are made from thin metal.

Next, “eye up” where its going to go, preferably with solar panel spoiler pointing to the front of the caravan/motorhome. Keep in mind when positioning it where you want the cable to pass through the roof, this would normally be into a wardrobe area or top locker or to a known pre-wired solar panel connecting point if you caravan/motorhome has one. 

Measure from the side of the van to make sure the panel is straight and then mark with a pencil so you know where to put it when the sealant has been applied.

The shorter the cable run the better as the shorter cables will give less resistance and less voltage drop.

Once you’ve decided where its going you need to give the roof a proper clean. If its green like on this van I’ve found that washing up liquid in a squirty bottle works really well.

clean motorhome roof

When the roof has dried  from that clean you need to then degrease the roof. This ensures the sealant adhesive can adhere properly. Use Panel Wipe or white spirit or similar, also degrease the bottom of the spoilers or feet to again ensure a super strong bond!

Up next is to open your selected sealant adhesive and with a fat nozzle lay down some nice beads on the feet or spoiler bases, you may need two tubes if its a big panel. Leave some gaps in the beads as opposed to totally filling them as it allows for the sealant to spread.

Last update on 2023-01-03 / Affiliate links / Images from Amazon Product Advertising API

Last update on 2023-01-03 / Affiliate links / Images from Amazon Product Advertising API

sealant adhesive for solar panel on caravan

Once thats on pick up the solar panel and hover over where your pencil marks are and push into position on the roof. Clean any excess sealant off (use Panel Wipe for this) and make a neat job, this video below shows a handy sealant trick that is quick and easy.

fitting a solar panel to a motorhome

Now that the panel is in position its time to drill the hole for the cable to pass through. Measure inside to a reference point on the side of the van (or roof) that can be remeasured on the outside so that you know roughly where your drill bit will emerge. You can use a tiny drill bit initially if you feel its not 100 percent certain, that way its not a total nightmare if your measurements are out!

Run the pilot drill though and all being good I then tend to use a small hole cutter as it make a neat hole that the cables can freely be passed through with out any ragged edges to chaff the wires.

solar panel wiring
solar panel wires passing through gland

Pass the wires through the gland that came in the kit and  then clean and degrease the gland and area where it sits over the new hole. Roughly lay the cable from the solar panel out in 90 degree angles (I always think diagonal cables looks wrong!) to the hole, the gland can then be tightened around the cable and the sealant applied to it. Press into position the gland, clean off the excess and tape down in position so it can fully cure.

  • Always fit the gland so the cable exit is at the back of it, this helps prevent water being driven into it when at speed.
solar panel gland fitted

To keep the cable from the solar panel to the gland tidy I usually use conduit. This normally has double sided tape on the back of it which I use to position it then run a bead of sealant either side to  fix in position. You can use plastic cable clips but I’ve found they come off after a few years or they go brittle in the sun and snap off  so conduit is my “go to” way. If you do use conduit leave gaps occasionally to allow water to pass through otherwise it acts like a dam!

solar panel wire conduit
Snap the top section of the conduit on once in place

Solar Panel Wiring

OK so we’ve got all the roof stuff done and watertight and we are now inside the caravan/motorhome with the wires dangling through the roof. Time for some simple wiring to get it all working.

solar panel entry hole
caravan solar wiring

If fitting a solar panel to a motorhome you can wire the feed from the solar controller to the leisure battery and also the engine battery so that in theory you should never have a flat engine battery. This can be more work if there is no dedicated solar connection point as you will have to run a feed/cable directly to the engine battery. In this installation the motorhome PSU had an input for solar which did all the labour intensive cable running for me.

So, the cable from the solar panel needs to be connected to the “solar input” on the controller that came in the kit, the controller then regulates the voltage from the solar panel and distributes it to the two battery outputs. This is where you wire in the positive and negative on each battery to.

caravan solar panel wiring diagram

Each battery needs to have an inline fuse on the positive wire (usually  a 15amp fuse is used) to prevent any damage to solar panel or battery. If fitting in a caravan you will only use one of the outputs from the controller.

  • The fuse needs to be as near to the battery as the installation will allow.
  • Connecting directly to the battery terminals is the most direct and efficient way to charge them.
  • Connect the wires into the battery clamps the same way as the other wires are connected on that terminal.
  • If your battery is in a battery box or sealed locker do not fit the fuse in it. Leave the fuse on the outside of these areas to prevent risk of fire from the gases released by some batteries.   
solar panel wires connected to the controller
solar controller fitted

This kit is from PV Logic and includes a MPPT controller that you can connect to your phone via an app, this can tell you all the voltages, amps etc that the solar panel is putting out…very clever stuff.

 If your controller is not a super posh one with its own app etc use a multi-meter and check what voltages you are getting from the solar panel and see what the batteries are getting too. All you do is touch the multi-meter probes on the screw pins on the controller to get a reading. The solar panel will put out up to 22volts in the sun which will get regulated down through the controller to about 14.2 volts to the batteries. 

Now sit back and enjoy all that free energy!

That is the basics of fitting a solar panel to a caravan or motorhome! I’ve left out how to connect a solar panel to a Sargent box or BCA box etc as every system is different with variants depending on year, I think it will just get confusing so its just a straight forward guide for now.

I hope this has been of some value if you are fitting a solar panel to a caravan or motorhome.

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     Please note these are the words and opinion of the author only. Neither the author nor the website can be held responsible for any errors or omissions. You should seek professional assistance if in doubt.