The 9280 is what I would choose. I would pull #3 or #4 wire, depending on type, but #4 is probably more than adequate for only 12 feet from a voltage drop point of view. That charger will rarely operate at 80 amps, more like 20 or 30 most of the time. http://www.armstrongssupply.com/wire_chart.htm
Brian
2005 F250 Supercab, Powerstroke, 5 speed automatic, 3.73 gears.
20 ft race car hauler, Lola T440 Formula Ford, NTM MK4 Sports Racer
1980 MCI MC-5C highway coach conversion
2004 Travelhawk 8' Truck Camper