The solar panel is to be installed on the roof of the van. I went for a semi flexible panel as they are light weight and will easily stick to the roof using no-nails. The panel I went for was 120 Watts featuring back contact solar cells which will give up to 22% conversion efficiency. It is also made from ETFE material which is very robust and less prone to cracking and corrosion. From the research I have done these panels give the best performance and are very reliable.
Connection from the panel to the controller was done using 4mm solar panel cable. I used inline heat shrink crimps which were also hermetically sealed when shrunk down. This was then covered over with another layer of heat shrink with internal glue. This made a very good water tight joint.
The control I went for was the Victron Bluesolar PV 75/15 75V 15A MPPT (max power point tracking) controller. I did spend some time researching controllers and found I wanted a true MPPT controller which will give up to 30% more power than a PWM controller. There are a lot on the market and some that say they are MPPT controllers are actually only PWM controllers check this link out. Also search on YouTube for some of the testing done on other controllers and you will soon see that cheap controllers are not worth the money, you will just be throwing money away. The Victrons are not cheap but when you consider the price you have paid for the solar panel and batteries its worth spending a bit on a good controller that will protect all this.
I also bought the blue tooth accessory which allows me to monitor the power going into the batteries from the panels and the amount of current being used by the van. It also keeps a history of all the power in and out from the batteries. Below I have shown some screen shots from when we went to the New forest for a couple of days running on 12v only.
To ensure I have enough stored power for a few days I have also installed a second 110 Ah battery under one of the rear seats. This is strapped to the floor and has a vent pipe going out the bottom. It is connected to the other battery in parallel. The wiring diagram for this set up is below. All the load of the van goes through the controller so the controller can protect the batteries from over load and shuts off batteries when they are too low.
The history screen shots from my iphone above are from a 3 night trip to the New Forest in May. The weather was not very good with most days overcast or raining. The position of the wan was in the woods a small opening in the tree canopy so sun light was not great. We did not use much power during the day except the occasional use of the water pump. Fridge was running on gas so not pulling much power. At night we watched some TV say an hour on 12v, lights where used and are normal filament type not LED yet. Water pump was used again and two phones where charged up. We was very aware that we was on 12v so where possible we switch devices off. Looking at our power consumption and the charge we got from the solar system I was very impressed. Three nights and we still had a good power bank charged up. I think in the future i will add a second solar panel as in cloudy days I am lucky to get over 20 watts from one panel. The controller i have bought will only take a max of 200 Watts. So I could add an additional 80 watts to this system.