Hey Folks, Since most (all, really) of my camping is dry camping, I'm thinking that I should add a second battery to my setup. When I bought my 99 Coleman Santa Fe last July it had no battery so I purchased a Group 27 battery for it, which works pretty well. If I add a second battery, does it need to be a group 27 also? Can I add a group 31 battery to get more AH? Any issue with that? Thanks!