I'm trying to figure out what my best option is for charging camper batteries. I have an older camper with a real basic 12v system, and I decided to install dual batteries with a disconnect and a small 1.5amp trickle charger during storage times or when I'm at a full service campground connected to 110vac to keep the batteries topped off. My areas of question is the charging relay in my "01" F-250, I've already figured out that I needed a 30 amp relay and fuse but the part I'm confused on is that when I'm charging two batteries wired in parallel, an when the relay opens does it only charge the battery that my incoming + charging lead is connected to? or both batteries at the same time or???. I've done a some looking around on the web and I've found ACR's??? (automatic charging relays) and from what I can tell these automatically charge battery 1 until it reaches the desired 13.7 volts then starts charging battery 2.Is this what I want or is it unnecessary?. My only other question is that I read on another thread is that someone combined the Aux. and the #4 pin charging lead to create a better feed so that there is not as much of a voltage drop. The question is, is this center aux lead ran through a relay ?? also is this a good idea??? I would appreciate any help I can get with this, Thanks.