Well, max charge certainly is affected by the weather... I've seen it as high as 13V on warmer days. The Solar Panel certainly charges at a higher rate in direct sunlight, so I simply open the hatch up in the back and park the car so the panel faces the sun throughout most of the day. I have a cable and lock running thru it, so fairly safe in my driveway during the day and my work has security in our parking lot.
I also put in a few switches to turn off my alternator... testing phase right now. I'll keep you posted, but I suspect the 13 Watt Panel will keep everything topped of since most of my commutes are under 10 miles. Panel charges all day when I'm at work. In a pinch, I can always turn it back on
I wonder if the switch is okay to turn back on while the car is on...?
Also got my LED headlights installed today... 36W combined... way lower than the 110W combined stock bulbs.