how much space have you on top of your camper?? I have had an 85 watts for 4 years now and even transferred for free when i changed the camper, and keeps the battery well and above it condition, we do a lot of rallies in this country and use aires in France on our way to Spain. so there you have it.
Just purchased the 120W version of one of these and fitted it to my dads MH. he is very pleased with it, does everything he needs and more. Sunstore where very helpful as well
If it is just for keeping a battery topped up during the winter storage then a 30W panel would be more than adequate, but if it is for use when using the motorhome off grid in the winter it is a completely different matter. The main issue being that the sun is very low in the sky during the winter and if flat mounted on the roof the panels are going to be producing only a fraction of their potential due to the angle of incidence. Not knowing what you usage is it is hard to give any advice as to size of installation etc. An option would be to put on panel on roof of say 80W - 120W and then have another ground mounted that you can adjust to get the best angles more maximum effectiveness. Unless anyone knows different I think you would need two controllers as the poorly performing panel would have a detrimental effect on the panel that was performing efficiently if they were connected through one controller.
With my tin tent I use 2 x 80W panels ground mounted and facing in same direction and routed through a 20A controller on 4mm solar cables. Using MC4 connectors and 'Y' adaptors I can then daisy chain up to 4 x 80W if I need to. In the summer I use a single 80W panel and I am a fairly heavy user with laptop, printer, TV etc.
------------- 'A sure cure for sea-sickness is to sit under a tree'