I believe they are 2/0 from the factory. They are thicker than traditional civilian 2/0 because the sheath is really, really thick. When I re-batteried mine with civvy batteries, I feel pretty confident the factory cables said 2/0. I replaced them with civvy 2/0 welding cable without issue. When you look at them, they look like something crazy like 4/0.
I did this a year + ago and since then I have:
Started the truck in cold-for-the-South temperatures in the teens.
Slaved another truck that was totally dead. Really dead, 0V in the batteries.
Moved my truck just using the starter, with the truck in gear.
At this point, I have stress tested the battery cables to a degree that I feel confident in saying the truck has lost none of it's reliability or "heavy duty-ness" with this changeover to civvy cables.
I have also powered a Warn 18,000 lb. 24V MRAP winch at the rear of the truck. About 15' of 2/0 welding cable. I have worked this winch extremely hard in testing to ensure it won't fail in the field (no one wants to be that guy in the woods with a dead winch). I have worked it so hard that I ran the voltmeter into the red with the engine running, drug my truck with locked up brakes, etc.
On my truck, the battery disconnect breaks the ground circuit. You will need to break the ground circuit for the batteries and the slave cable: when I did mine initially, I left the slave port negative cable attached to the battery like it was from the factory. What I found was that the batteries were able to ground to chassis through the slave port where it's bolted to the cab. So my slave port and chassis ground strap go to the switch, then a short 2/0 cable connects the switch to the negative post on the rear battery. With the switch open (off), there is no path to ground for the batteries.
The winch switch interrupts the power wire, so there isn't 15' of live wire under the truck where you can't see it when driving. Imagine throwing a piece of debris up and severing the cable while it's hot.
and yes, the labels are temporary. When I paint the truck, I have some other labels I have to create and reproduce. So I'll peel the tape and do something more professional.
I soldered the lugs on and I got everything HOT (torch!) in order to avoid the cold solder issue that Recovry4x4 and others had warned of. So far, no issues. I preheated the copper strands in the cable as I was heating the lug. You can usually tell when the cable is too cold, as you put it in the solder you've melted into the lug and it immediately solidifies. That's the cable absorbing all the heat.
