While doing some net cruising on 12 volt systems I ran across the amazing fuel cells that run on methanol and produce electricity, they never run down, never need recharging. They produce 140AH/ day and have a continuous output of 5.8 Amps on top of all that they only weigh 28 Lbs.
http://www.marine-fuel-cell.com/index.html
And now the bad news they cost $8500! US