House batteries are commonly 12v wired in parallel. With this kind of a hook up the weakest battery drains the best battery. It is far better to use 6 V batteries wired in series. this way there is no current loop draining the cells. 6 V golf cart batteries are deep cycle and work very well if you can fit them in.
6 V golf cart batteries are deep cycle and work very well if you can fit them in.