The thing is there is not just 1 way to do a dual bat setup and everyone has their opinion on what is best. There are also a lot of myths and hearsay and you will have as many differing opinions about it as you have about tires, lifts, etc.. It basically comes down to what you want the setup to do. You can go the easy route and just connect em in parallel which gives more cranking power but does not isolate the battery. Then there are different isolater setups from actual manufactured isolaters to manual switches to solenoids to running 2 alternaters. An article could be written but it would be quite long as there is no 1 right way to do it.