I have a solar panel for my Westy (it'll work with ANY van) and it is 
wonderful - quiet, powerful enough to keep me well charged and very portable.
I use a single, used panel that puts out about 18-20 VDC at about 3.5-4 
amps through a conroler and some 20 feet of line to a plugin for the battery.
The whole thing cost me about $250 in materials and barring any really 
stupid acts on my part, should last for another 30 years at just about 
the same output.
Anyone interested in more information, drop me a line - I am really sold 
on the idea and end up talking to a LOT of folks in the campgrounds we visit.
Jack