Lead/Acid are typically around 1.23 lbs to 1Amp, the Meridian AGMs
listed by Paul are around 1.23 or so, which is around the same as the
Optima batteries I saw also highly recommended. The evercel would
have been around 1.79 for the typical
golf cart batteries and I think their marine batteries were higher, but
you can't find them on their website anymore....

Meridian Group 27 73AH 59lbs

NiMH, LiPO, NiZn are all potentials in the running. Fortunately, we
have someone even more interested then catamaran sailors looking into
this, the electric car and hybrid car industry. It's on those
websites I really find the most information.