I installed a Waeco 12V CR110 fridge to replace the original Dometic 90 litre 3way fridge in our Goldstream camper, then needed to install a second 120Ah AGM battery to cover the expected 70 Amp hour power consumption of the fridge and lights etc in hot weather.

Our 110 Watt folding solar panel had nowhere near the capacity to keep both batteries charged, so I decided to buy a 120 Watt flexible solar panel and glue it to the roof of the camper. The panel is a mono type and comes out of China costing $300. It measures1060 x 800 x 3mm thick with an aluminium sheet backing and weighs around 3kg.

After getting the panel I had to go away with work for a month and during that time thought long and hard about mounting the panel on the roof. In the end I decided this was not a good idea, as it meant we could not set the camper up in the shade. The panel would also only have a good angle to the sun for a few hours each day, when we really needed the maximum input from both panels.

I came up with the idea to make a frame for the panel so it could be used just like a standard portable panel. I drew a diagram of what I wanted the frame to look like and carefully worked out the sizes needed, making the frame just slightly larger than the panel as it has sharp edges.

Then it was off to Bunnings to get some Connect-It 25mm square aluminium tubing and plastic connectors. Of course they don’t come in the lengths I needed so the tubing had to be measured and cut with a metal cutoff saw, which I just happened to have in the shed. Luckily wastage was not huge, as this stuff is not all that cheap costing around $150 for tubing and connectors. It all went together very easily with the help of a rubber mallet and is also very light and strong.

Both the frame and back of the solar panel were cleaned up so there was no dirt or oil on them and one side of the frame coated with marine Sikaflex adhesive. The panel was dropped onto the frame and clamped down with a little weight applied to the middle of the panel and left for 24 hours to cure.

The back of the panel after the adhesive has cured.

The 4.6 sq mm twin cable connects to the rather small front mounted junction box and terminated with an Anderson plug screwed to the side of the frame. A 10 metre lead connects this to the camper solar input Anderson plug.

The finished panel

Stainless steel hinges are attached and legs made from 25 x 3mm aluminium riveted to the hinges. I have also drilled a 5mm hole near the bottom of each leg to put tent pegs through if the panel looks like being blown over in strong winds. A handle is also riveted to the top of the panel for easy carrying.

The panel does not have a regulator mounted as I believe the regulator should be as close as possible to the batteries to reduce voltage drop. The panel has direct connection to the Redarc BCDC1225 with its inbuilt MPPT solar regulator. With the panel angled towards the sun it produces 7 to 8 Ah which is quite good.

The whole panel weighs less than 5kg and is far lighter than the 15kg of the 110Watt folding panels we have. All up its probably not worth the expense of doing this but I had the panel and wanted to make better use of it.

If I were to do it again I think I would get two or three 50 Watt panels of this type and make up a frame so it was in effect a folding system which would take less space and weigh even less.

 

thanks to Kevin Beckwith for this article

 

 

march 2013