RamGazer

Melted power cable.

gcssr

I assume this is the passenger side battery, the leads under the nut are probably from the alternator, the thru bolt corroded and not able to make good contact, causing it to arc, also look at all terminals for corrosion, causing high load from alternator, the alternator charges the right side battery and cross charges the left battery, when cleaning battery terminals always remove the thru bolt and clean any corrosion and reinstall the bolt, do this on all battery lug bolts, hope this helps you, and anyone else;;

RamGazer

Yes, its the passenger side battery. I replaced the cable this morning but when I try to start the truck it won't start and all my guages freak out like starting it and turning off multiple times and beeps. I'd show a video but this site won't allow me to.

StealthDiesel

If you do a search on "passenger side battery over-charged" or something similar, you will find a ton of threads on this issue and why it happens.

You don't mention it but you have to clean the driver's side battery connections also. A bad connection in the cross-over cable is what caused your issue.
Plus test each battery separately while you have them disconnected from each other.

I recommend to double up the cross-over cable with another heavy duty cable. This is easy to do and will help greatly to prevent passenger side battery issues in these trucks.

gcssr

Have you cleaned all terminals, remove and check the condition of both batteries, double check all ground connections, remember the drivers side battery is charged off of right side battery, the alternator charge the right battery, if there is a bad connection it will over charge the right battery and continue to demand a greater charge rate until it burns the battery up by over charging, in the mean time the left battery will go dead from no charge, this battery system on these trucks sucks, I had wally world burn my batteries up by leaving a clamp loose on the right battery, I told them do not touch any thing but oil change, they don't follow instructions,

AZdieselburner

This happened to a buddy of mine a few weeks ago. Turned out to be the relay on the grid heater was stuck ON.
It's worth checking that out.