The Vmp of the 50W panels seems to be close enough to the Vmp of the 100W panels that there shouldn't be any issue putting them all in parallel. Alternatively you could put two 50W in parallel then in series with the 100W panels.
Yeah, I wondered about that. Basically it seems like these particular panels (the 50W and 100W Renogy) do provide a lot of options thanks to that. What you *can't* do is deal well with odd numbers of panels terribly well. As long as you stay with even numbers, the options are much better. I'm just conflicted with my want to cover the roof. I want that for two reasons...the obvious is to maximize solar electricity output, the other is to cover the roof with a layer of "insulation" from sun.
To be clear, my idea of layout is three strips down the van. Two long strips that are 1x50W and 2x100W on each side of the fans, then one strip in the middle that's 1x50W and 1x100W. But that gives me an odd number of 100's and an odd number of 50's. As you say, I could possibly get away with turning two 50's into looking like a single 100, which evens things up. And if I give up that odd 50W in the middle, then I can still use one controller. Those voltages are CLOSE, but not the same, so it bugs me to maybe lose a tad of efficiency there.
My temptation is to put 4x100W on my current controller and buy another identical controller. It's only $300. Then I would parallel two 50W and add them to the left over 100W on that controller, so any inefficiencies are minimized and I have some redundancy.
--Donnie