I just finished mine and I can tell you there are several different ways to do it, based on what you want to accomplish.
Iam using a pac-200 giant relay, that basically just splits the out put of the alternator to the two batteries and keeps everything isolated. A bid ass fuse before the relay, and a switch that takes the relay out of the loop if I want to.
There was an exhaustive thread on this in outfitting last year. Doa search for that, we covered just abiut every possible permutation and philosophy. Useful stuff. It helps a lot if you know why you need a second battery...
Old thread here...rise old thread and answer me this question!
For light use would not a yellow top single battery do well enough for the occasonal
winch job, keep the motor running windh a lttle rest a little, For casual fireroading why weight down the grig and spend the $ for the outside chance you'll winch long enough to bugger starting the rig?
You guys that go out and work at getting stuck then pull each other out, I see the dual set up being the way to go. Redundancey and all that, big lights, loud music. I just boink around and might highside or slide off a road....ONe BAttery?