I'm using a pair of Deka AGM 6 Volt Golf Cart Batteries, they cost me $200 each and they are American made. After going the six volt golf battery route I will never go back to the 12 volt deep cycle type pairs. The AGM type eliminates the need to water them, a big plus if you have poor access.
You can run them way down and the recovery seems to always be 100%, in fact mine test more amps now then the day I bought them.
Having a good multi stage converter/charger is the most important thing to help ensure a long battery life IMHO. My old single stage converter destroyed my first set of wet batteries in a very short time, it would just boil them to death.
