When I was putting the Inverter into my system [and mine's 12 v., too, though a 2500 W. inverter], a buddy of mine who is a physicist was visiting a few days and fascinated with the pv, etc. He said, in relation to a question I had that mirrors yours, "Between the batteries and the inverter, don't scrimp on wire gauge. After you calculate the gauge you need, make that your bottom line and then go as large as you can stand." Of course, as the previous poster said, you gotta be able to connect it to the terminals, which will ultimately limit the connectors you choose and use....