I don't know how many on here have Ram Cummins trucks but maybe someone will see this in the future and possibly help them out or even save them some money.
I have seen this personally happen twice in two years on two different trucks (not mine). If this happens it can be dangerous, and could burn your truck to the ground. The trucks that this happened too are 2005 and 2007 so in reality if you have an 03-12 Cummins you have the same chance of it happening to you.
First l want to explain how the charging system works. You have two batteries, one on the passenger side of the truck and one on the drivers side. The two batteries are hooked together with a cable that goes from the positive post on the passenger side across the radiator to the positive post on the drivers side. The battery on the passenger side has the starter and alternator charge wire run to it. The drivers side battery is where the computer is hooked in. The computer tells the Alt how much to put out by how much voltage it reads.
Okay here's what happens. The cable that connects the two batteries together is on a stud on the drivers side battery. That connection gets corrosion between it and causes loss of connection between the two batteries.
Now remember earlier when I said the Alt charge wire is hooked into the passenger side battery? What is happening is that the computer is running off of the drivers side battery but when connecting cable looses it's connection it does not get a charge because of the Alt being connected at the passenger side battery. The truck will run until the drivers side battery runs dead. The truck will die. You will go to try and start the truck back up and it will crank over great but will not start. Remember, the starter is hooked to the battery on the passenger side which is the battery that is also charged. As the drivers side battery goes down the computer will tell the Alt to turn up the juice and if run very long like this it will blow the passenger side battery apart.
There are shops that will sell you batteries and an Alt telling you the Alt was overcharging the Batteries. The fix to this is keep all the connections clean and protected with a battery terminal protector. Just cleaning the the battery posts and terminal won't cut it. You have to remove any removable wires from the terminals and clean those too.