What batteries do you have now...
My recommendation is most always the same G-2's or L-16's depending on several things.
WHY
Group 24 MARINE/deep cycle or MARINE/rv.. abot 75 AH each you can use perhaps 25% before damage (Fast aging) Sets in)
Group 27, 29 and 31 just under 100, over 100 and 120-130 respectively.
GC-2 Pairs are DEEP CYCLE Golf Car batteries. you can safely use HALF the power before rapid aging sets in.. and that's 1/2 of 220 Amp hours give or take 10.
The L-16 is nearly tx that (Also used in six volt pairs)
Watts (amp hours time volts) per pound is nearly identical across all lead acid batteries. Flooded wet, Maintenance Free and AGM.