X2 for RoyB's post! I posted on this same subject about a week ago. Number 1, once you have severly discharged the battery it is toast. Two, RV's do come with a cutoff switch, BUT, they wire a lot of things around them, and the parasitic draw will kill a battery in two weeks or less! Three, it seems manufacturers are installing the cheapest batteries they can in the newer RV's. First, install a disconect at the battery, so that nothing is powered when off. Second invest in a good DEEP CYCle battery, remember if it states CCA's or cold cranking amps, it is NOT a deep cycle battery. Deep cycles are better able to withstand discharge and chargeing. Depending on your usage, i.e. Dry camping etc. you may want to install multiple batteries to give you more amp hours, but most important install deep cycle batteries! Good luck!