Solar Panels?

I am considering solar panels for the van (Merc Vito Autosleeper Montana Hi-top).

The 12V system runs the water pump, Propex fan, lights (most of which I have changed from fluorescent to LED) and charges phones/tablets; the leisure battery is 90Ah. There is a fridge that has 12V as an option, but that runs from the vehicle battery, and only when the engine is running (relay actuated by alternator current to battery); alternatively 230V with a hook-up, or gas.

There will be times when we will be off-grid for 4 or 5 days at a time, so I'd like to tap the "hive-mind" here:

• Is it worth getting a (portable) solar panel for charging the leisure battery?
  
• What might be an appropriate wattage?
  

Thanks in advance,

I'm (almost) certain there was a Montana owner here in the recent past who fitted solar to his roof - it would be worth doing a forum search to see if you can find the thread.

Otherwise, it seems generally accepted that for the loads that you expect, a 100W panel is a pretty good starting point. The real battery hog is if you have a compressor fridge (you don't) and if you have a television and watch it a lot (you don't appear to). Two 100W panels should easily fit on a Montana, though for your usage that seems a bit over the top.

IMO, the best solution is a fixed panel - far better than a portable panel because it's always there and working - you don't have to keep remembering to put it out and turn it, and you don't have to worry about people nicking it while you're away from the van - and you don't have to find somewhere to store it, which in a smaller van can be difficult. Having said that, most campsites are pretty safe for leaving stuff out - but it is a relatively expensive piece of kit. And a fixed panel should keep both your batteries topped up during the winter, with the right controller.

We have a stuck-down semi-flexible panel on the Trooper - not everyone likes this option for various reasons, but it's hard to deny that this is probably the lightest, most compact and discrete way to implement solar on a high-top.

Hi Tetenterre,

I just added a solar panel and controller to my 1993 Clubman, and although you have a different van, the basics should be pretty similar and might give you some ideas. Here is the thread with pics [You must be registered and logged in to see this link.]

Roger

Thanks, both, especially for the advice on wattage.

@Roopert: Idea behind portable is that I can use it for other purposes. (eg One of the things I do is astronomy outreach, and it would provide power for my solar observing kit - laptop, camera, tracking mount).

It also enables me to park the van in the shade in the summer heat, and still charge the battery by chasing the sun around. One option I'm playing with is to use an old telescope mount to have it track the Sun, so it's always directly facing the Sun, and getting max benefit.

@Roger: That is very useful; bookmarked.

I had solar panels on my boat for a few years and have never been convinced that tracking the sun actually gave that much benefit. It will give some improvement if keeping the sun at 90 degrees to the panel, but it will also use some power to achieve that. During the height of the Summer, the sun is pretty much overhead anyway for the best part of the day even if the panel is flat. The other thing to remember is that many British days are overcast, so having a flat panel is going to be receiving most of the light anyway. Unless you are using all the power that you are generating, you are probably going to use less than the panel gives you. Even draining your battery to 60% of capacity is only going to take about 8 hours of sun to recharge a 100ah battery in the Summer months.

Roger