Sirius018

Anyone ever done this, if so how difficult or easy and how would I go about doing it. The space is there for the second battery is it as easy as dropping in the battery and wiring it in or do I need to go more in depth with the install.

I want to add the second battery onto my 04 2500 hd with the 6.0L

in2pro

depends how what you intend to power with it... there are several ways to do it..
the easiest is to just come right off of the fuse box from one of the 2 studs, one is for the trailer the other is an aux terminal.
I just went from the larger stud with an 8ga. wire and added a ground cable to the chassis.
Now this setup will not add to the starting power, nor will it prevent both batteries from being drawn down (tho it will give you double the reserve power for running options like the radio and other accessories) as there is no isolator in line and basicly back feeds into the system (except for starting)
I set mine up this way to keep my camper battery charged when off of the camper(not in use) the tray was just too convenient.

I also use it to jump start those that may need a jump as I only need to disconnect a quick wing nut to isolate it from my system.

I believe it was Hardin Thicke on here that did a nice write up on adding an isolator so the battery is separate from main battery.