If anyone saw my post in another thread, I have now got two 100w panels , one free, now, I have two 85 ah battery's, and fixed the one panel on the roof and over a long weekend could no where use all my electric, so I have another panel lieing about now, tried it loose on the roof yesterday and it seems to do the same as the other, now thinking of putting it on as well, but do I need it , will it be any benifit or will it fry my battery's and just be a bit more weight to lug about.