Caravan solar panels; how to mount them correctly so they stay on

Solar panels are one of the most commonly fitted accessories to Caravans, Hybrids and Camper trailers today, and for good reason. Permanently mounted solar panels are a breeze for keeping your batteries topped up up and can allow you to run some pretty incredible 240V appliances in the middle of nowhere, if you have the right battery and inverter system.

However, there’s a lot of different ways in which you can install solar panels to the roof of a Caravan or Hybrid, and I can tell you from personal experience that they don’t all work, and that’s pretty scary, and dangerous.

On our very own Reconn R2, we had one solar panel that was installed by Lifestyle when it was built, and then a secondary panel was installed by someone else using a different method.

One day, after months of owning our Reconn R2, we arrived home to find that we only had one solar panel on the roof; the other one had been ripped off somewhere between Albany and Perth.

You can read more about this here – Where’s our solar panel gone, but in essence one panel was mounted well, and the other was not.

In this post, we cover everything you need to know about mounting solar panels correctly, and have just completed installing 3 new 200W solar panels on our Reconn R2 camper.

Risks of improper fitment

If you install a solar panel, and it comes off somewhere along the way, you put anyone behind you at major risk. In fact, in 2020, 3 people were killed in Tasmania allegedly trying to avoid a solar panel that flew off a caravan.

Please let that sink in for a minute, and then have a look at photos of A pillars that have been crumpled in from panels coming off and hitting the vehicle behind.

The average solar panel is somewhere between 6 and 18kg, and that’s a lot of weight to have flying off the back of a caravan.

Beyond the above (not that you should need anything further), you can do serious damage to your van and other peoples property when a panel is ripped off, and at best its going to make your travels very difficult.

How often do solar panels come off?

Since writing the above post, where we shared why the panel came off, and advised people to check their panels, we’ve had a number of comments saying that there are panels all over the country, up and down the highways that are getting ripped off Caravans.

With the huge explosion of travel, its pretty shocking, and I guarantee there are thousands of incorrectly installed solar panels on caravans and RV’s around the country!

Installing Caravan Solar Panels correctly

After losing a panel ourselves, and knowing we wanted to fit more solar panels, I decided that I’d thoroughly research this and come up with a setup that is bulletproof.

I don’t want another panel coming off, and spent a fair bit of time looking at different options, and have gone with the same setup as Lifestyle use from their factory, which has proven to work very well.

Disclaimer: This is just our installation method, and we take no responsibility for your panels not being done correctly. Please do your own research, and get the panels professionally installed if you are not confident.

Installation overview

We had 3 solar panels to be installed, all 200W each, and weighing in at 12kg each. We went with peel rivets to hold 50mm aluminium angle to the solar panel in 4 places, and then Sikaflex and to hold the aluminium angle down onto the roof.

1) Find a suitable location

Before you commit to mounting solar panels, you need to get onto the roof to see where they will fit, and ensure that the roof is solid enough, flat and going to allow for the cables to be run neatly. 

2) Work out how you are going to install them

Based on previous reading, and the Lifestyle mounted panel that has been bulletproof, I knew that aluminium angle was probably the best way to mount it, and getting majority of the strength by using Sikaflex would be the go.

You can get plastic solar panel mounts which I don’t like at all, and don’t recommend using, based on our previous experience of them ripping off.

3) Liaise with the professionals

Sikaflex is the industrial standard for a heap of applications, and I was happy to pay a premium for their product. In the grand scheme of our lithium and solar upgrade, its cheap.

I simply sent an enquiry to their technical line, and someone phoned me a day or two later with all of the information needed. For us, we’d be gluing an aluminium angle down onto an aluminium roof, and I know when done well, you’ll never be able to rip the angle off even if you tried.

If you’ve not experienced how well this can stick things together, know that its literally used to hold things far more complicated and important than solar panels on.

Even your cheapest silicon with average preparation has the ability to be insanely hard to remove, so when done well with the right product it should be bulletproof.

The technical line recommended using Sikaflex 252 for joining aluminium to aluminium, with the right surface prep.

They explained the process of using the activator and primer, and that the finished thickness of the Sikaflex should be no less than 3mm! Another important step that I’m sure a lot of people ignore (the panel that came off was far less than this).

From there, we were told that any mechanical fasteners would impair the use of a flexible adhesive, and that if we really wanted to install them it should be done after full cure, which is 5 to 7 days. Yes, if properly prepared, you don’t need any screws or rivets.

4) Buying the materials

Solar panels to suit your system

50 x 50 x 3mm aluminium angle

Peel Rivets to suit the depth of your roof and panels

Sika Tech Aktivator-100

Sikaflex 206 G and P Primer

Sika 252B (we used one 300ml tube per panel)

Scotch Brite

Paper towel

5) Attaching the angle to the solar panels

There’s a fair bit of work that you can do to the panels before you get onto installing them.

I cut two pieces of aluminium angle to mount the ends of each panel down, and then chose to install a 400mm piece of angle on either side of the panel in the centre, to give it even more surface area and to stop the panel from sagging over the 1650mm length.

In total, we ended up with two lengths of 670mm angle, and two lengths of 400mm angle per solar panel.

Pre drill all of your holes in the angle (including any going into your roof if you want to go that way), and then attach it to the solar panel, flushing the top of the angle to the top of the panel.

I offset the rivet holes down a little to keep the rivets well away from the panels glass.

If you want to have the panels higher off the roof, step the angle down a bit to do this. We’ve gone with about 20mm clearance from the roof, which I think is more than enough.

6) Preparing for the Sikaflex

Sikaflex advised three items to prepare the areas, and gave us an email explaining how to do the process.

Interestingly they advised not to use fasteners with the Sikaflex, but if we did, to wait 5 – 7 days for the Sikaflex to cure before doing so. How many people do you think Sikaflex them on, and screw straight in?

How many people do you think don’t prepare the materials properly, or don’t bother with cleaning or activation?

I simply put all 3 panels onto the roof of the Camper, marked where I wanted them to sit and then removed them, and on the day of installation prepared the surfaces, and put the panels on.

I picked the most level locations, where weight distribution would be good and lined them up with the edges of the roof for easy alignment.

7) Installing the panels

When a sunny Saturday finally arrived, I arranged to install the panels with the help of my Dad.

The first thing to do is the surface preparation, which involves using Scotch Brite or a scourer to rough/clean both surfaces up and clean anything off.

For aluminium, you end up removing some material, and we found wiping the area regularly with a rag kept it going well. 

One the area is thoroughly clean and any surface treatments removed, wipe the entire roof down.

Make sure you do both surfaces; the roof, and the aluminium angle that the panels are mounting to the roof by. This process took about an hour with two people going at it.

Apply the Sika activator 100 using a wipe on/wipe off method, and allowing it to flash off for a minimum of 30 minutes and maximum of 2 hours.

The data sheet suggests using a damp paper towel (with the activator), and each wipe we removed a heap of aluminium particles.

I used one portion of paper towel for each wipe, and so each piece of aluminium got a new bit of paper towel. Again, do the same for both surfaces; the roof and the panel.

We went through about 20 pieces of paper towel, throwing it out each time. every side was used. As I wiped it on, Dad wiped it off with a fresh piece of paper towel

The activator needs to apply damp and not wet for it to work properly, and the time you leave it on for varies based on the ambient temperature.

From there, apply the Sika Primer 206 G + P with a paint brush (which was supplied), and allow it to flash off for a minimum of 30 minutes.

This is applied with a paint brush, and should be done evenly, but fairly thinly. It’s black, so you can see clear as day if you’ve missed any sections. Again, apply it to both surfaces. 

When it comes to putting the primer on, make sure you have things well marked out.

It’s black, and sticks out, and if you just have a couple of little markers drawn on the roof you’ll end up guessing where the primer needs to go, and get some overflow.

Then, apply the Sikaflex (we did it to the angle on the panels rather than the roof), using as much coverage as possible.

I decided one tube per panel would be perfect, and it was. We ran beads around 8mm in diameter, and I did a rectangle all the way around each angle, and then a number of cross sections in between.

On each panel, we gave special attention to the angle that runs towards the front of the camper, knowing this is going to be the most likely to lift off first with the wind rushing past.

We then carefully lifted each panel into place, and dropped them down.

Make sure you’ve sorted your cables out before doing this, and that they aren’t tied up under the panel or you’ll never get them out after! We ran the boxes as close to where the cables had to go, to reduce the cable runs and weight etc. 

I didn’t put any weights on the aluminium angle as I wanted to retain the 3mm finished thickness, and they sat well enough on their own. I did give the panels a minor move back and forth when placed down to spread the Sikaflex a bit more and ensure a good surface area.

You really need two people doing this job, or it would be seriously slow and frustrating.

We did the panels in one go; all of the Scotch brite work first, then the activator, then the primer and finally the Sikaflex, and just kept working, rather than doing one panel completely, then moving on to the next (which would take a long time with the delay in waiting for the activator and primer to go off.

8) Final tidy up

After the panels were on, and we were happy with the gaps and their location, we used some soapy water to push any Sikaflex into the channels, and smooth it all up.

I decided to get some black silicon to fill any obvious gaps around the aluminium angles, particularly at the front where it could catch any air as you drive along. Any big bits of Sikaflex that came out I left to dry, and cut off at the end.

What did we pay to mount the panels?

1 length at 6.5 metres of aluminium 50 x 50 x 3 angle $55.23

1L of Sika activator – $56.57

250ml of Primer – $43.08

Sika 252B x 3 – $31.68 each

Rivets – $5

Total cost: $255

Ironically, you use about 1/100th of the activator, and a small amount of the primer, but its a small cost in the scheme of things.

How much weight did we add?

Panels – 36kg for all 3

Aluminium – 5.1kg

Rivets and sikaflex – 1kg

Total weight – 42.1kg

How long did it take?

In total, I probably spent about 3 hours measuring, cutting and drilling aluminium/solar panels, and then putting rivets in.

On the day of installation, it took Dad and I about 4 hours to scourer the roof, apply the activator, then primer and then sikaflex, and lift them up. The slowest part is the preparation, and installing the actual panels is super fast.

Can you just use Sikaflex?

I guarantee there are a huge number of people that just wipe surfaces down, scuff them up a bit and just install panels on with Sikaflex, without the aktivator or primer.

Of course, you can do this, but there’s a chance it won’t adhere properly, and if it comes off and kills someone, you’ll pay for it down the line. We did everything by the book, and as well as possible, and I’d recommend you do the same; use the Aktivator and Primer too.

Replacing the gas struts

This extra weight wouldn’t normally be an issue on a Caravan (assuming you are well under your ATM, and GCM), but we needed to replace our roof struts as they were already struggling without the additional weight.

I picked up 4 new struts with a higher pressure in them for about $66 each, and swapped them over, from Struts West. If the ball joints were the correct size, he’d have been able to make them up in a day, but they ran a slightly different size so we had to wait a week.

When I first put the panels on the roof, I thought I’d try and lift the roof up just to test how hard it would be, and it was seriously heavy.

I really wanted to replace the struts before putting the panels on, but it worked out badly with the timing so we had to lift the roof to change the struts with the panels on, which was a bit of a challenge.

The old struts had 180N written on them, which should mean 18kg of force, and we opted to go for 250N ones, knowing that if they weren’t strong enough we could add more pressure, but you can’t take it away.

It’s a fine line with this system, as you want it to be easy enough to lift, strong enough to hold the roof up (as there’s nothing else to hold it up), and easy enough to pull down.

Other considerations

The perfect Sikaflex may vary

We were recommended to use Sikaflex 252, to join aluminium to aluminium. Not all caravan roofs are aluminium, and not all mounts are aluminium either.

Its critical that you get the most suitable Sikaflex for your application, and it might not be 252!

Make sure you maintain an air gap

In almost anything in life, heat kills. Solar panels are no exception to this, and the hotter they get, the worse they perform and the shorter their life span will be.

You always want an air gap under the panels to allow for air to cool the panels. On the panels we’ve just installed this is only about 15mm, but the other panel was marginally higher off the roof.

Block the entire front off

One of the best things you can do for longevity and security of your panels is to ensure no air can rush underneath the panel when you are driving along at 100km/h.

This was one of the major differences between the panel that came off, and the Lifestyle panel that is still installed.

If you use aluminium angle to block the entire front of the panel off, no air can get under the panel and lift it up, and pry it off.

I even went along after the Sikaflex had cured, and filled in the gaps where anything was missing, just to stop air from getting underneath the angle and making it want to lift.

Why not semi flexible panels?

I looked at semi flexible panels, which are much lighter, and nice technology. My research with these is that they are not as reliable as solid panels, and the primary reason for not getting them was cost.

They are almost always double the price, and although I would have liked the reduced weight I didn’t want to spend that sort of money. We have plenty of weight capacity on the camper and rigid panels that we’ve proven seem to work really well.

We used Peel Rivets

If you’ve never heard of these, don’t feel bad. I hadn’t either, but they are a pretty amazing product. As pictured below, instead of pulling up like a normal rivet does with part of the stem snapping off inside, the rivets peel back in 4 places, and you end up with a flower head on one side.

I really like these for two reasons. The first, and most important is that it hugely increases the surface area being bitten into, and this is important as many solar panels have two skins on their vertical end.

When you drill holes through the panels (on their ends and sides) you’ll go through two bits of material, and when I used a normal rivet it bowed the inner skin in a lot, and I wasn’t happy with it.

The peel rivets spread much further and seem far more secure (I ran them on our previous soft floor camper solar panel setup too).

The second reason I like these is that you end up with no stem left in. Aluminium rivets use a steel stem, and when you put aluminium and steel together you end up with corrosion.

Sure, this is a long term thing, but eventually the rivets corrode because of the two dissimilar metals. 

Keeping the roof waterproof

If you intend on using rivets through the roof, or screws, you need to make sure its waterproof. Water ingress in a caravan can be hugely expensive to repair, and prevention is far better than cure.

If you do put any mechanical fasteners through the roof, make sure your Sikaflex does a circle around it, so no water can get into the roof between the angle and the roof itself.

A dob of Sikaflex on top of the screws or rivets never goes astray, completely covering them and making water ingress impossible.

Working out the right Sikaflex quantity

I guessed that 3 tubes would be correct for our application, with 3 panels, and then second guessed myself. Fortunately, you can work out how much Sikaflex is needed quite easily. Simply multiple the bed width by the bead height, and then the length.

For example, a 7mm bead by 7mm bead multiplied by 1.5 metres gives you 73.5ml of Sikaflex required. Our panels have two sides at 670mm, and two at 400mm, giving a total length of 2140mm of aluminium.

Multiply that for two, for two runs of Sikaflex and you get 4.28 metres, which would require 210ml of Sikaflex. 

If we do some extra squiggles, we should have plenty to get good coverage with a 7mm square bead and using 300ml of Sikaflex.

I figure more is better, so that’s what we are rolling with. In the grand scheme of things the Sikaflex is cheap, and not something you want to skimp on.

Why not Solar panel Z brackets for mounting?

Renogy, and now Redarc sell solar panel mounts that are in the shape of a Z, and work pretty well. I liked the idea, but they don’t have enough surface area to be glued down; they are designed to bolt to roof racks, and not to be Sikaflexed down.

You might get away with it, but we wanted maximum surface area to block the air flow at the front, and to glue the panel onto the roof.

Read the data sheets

Each Sikaflex product you get comes with a data sheet, which explains how to use it, the timing required for its use, how to apply it, and the PPE you need to wear.

I just had gloves on and safety glasses for the activator and the primer, and the Sikaflex is good to roll.

Cleaning Sikaflex up

If you need to shape the Sikaflex, get some dish detergent and water, and wet your fingers before you mould it. Keep it wet, and it won’t stick to you.

This is important, or you’ll end up with a massive mess that is not much fun to clean up.

Would we do anything differently next time?

After using these panels full time for about a year, on all sorts of roads and conditions I’m really pleased with them. That said, there’s a few things I’d do differently

More air gap

As it stands, we’ve got about 20mm air gap under the aluminium extrusion of the panel, and probably about 40mm from the panel itself.

However, with all of the angle around the panel, the heat gets trapped in and you can visibly see it on a warm day, whisping off the panels. A bit more air gap would be helpful for solar panel efficiency.

Install channels instead of angles

Our installation method is rock solid, but what happens if you want to replace the panels, or go to something different? Some panels are the same size, but if they aren’t, how do you use the same mounts?

I’ve seen installations since where they’ve stuck aluminium extrusions down, which you can attach to in different points, and this is smart for future proofing your solar panels.

Install more panels

For most cases, our 720W of solar on the roof is enough, but there are times where we could do with more, and given we could have fitted 1000W of panels on the roof, we probably should have.

Hopefully this has been helpful for you to install caravan solar panels correctly, or at least to validate that your ones are done well and aren’t going to come off!

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