I run two 6 volt Interstate Extreme Cycle GC2-ECL-UTL batteries wired in series. I get 12 volts this way and 225 amp hours @ 20hr and 447 reserve capacity minutes @ 25 amps. Weight is 62# each, which is the same for any group 29 12 volt dual purpose battery. You cannot EASILY buy true 12 volt deep cycle batteries anymore. All the common 'deep cycle' batteries that you see for sale at Walmart, Autozone, Napa, etc are actually dual purpose batteries. They don't have the capacity nor the life of a true deep cycle. For example-
Autozone Duralast Marine 29DP-DL
63.3#, 106 amp hours at an unspecified rate, 210 reserve capacity minutes at an unspecified rate.
Two of these wired in parallel gives you 126.6#, 212 amp hours, 410 reserve capacity minutes.
You also get shorter life, you better not discharge the batteries below about 75% capacity or charging capacity and battery life suffer greatly, and you also get less capacity. Golf cart batteries are true deep cycle batts and are designed to withstand deep discharges, have great capacity, and still give decent life. The only problem is that they are expensive. Roughly $150 each for mine. Compare to the Duralast at roughly $95 each.