I will try and make this short........while driving my voltmeter was staying around 11 volts then dropped to the bottom. Found passenger side battery boiling. Unhooked it at the battery. Charged the drivers side battery as it was dead started it noticed arcing and smoke at positive terminal drivers side. Unhooked the positive wire that goes to the passenger battery and all is good. And showing 15 volts on the dash meter. Just before I bought the truck the previous owner had replaced the passenger battery I assume this problem is related to the last one. Ideas? Short in the passenger battery? Short in the alternator?
Just realists my signature is not filled out will do that now
Thanks

 

Clean all posts (MOST IMPORTANT WITH DUAL BATTERIES) and check voltage at each battery disconnected. I had one battery have an internal problem and it was dropping voltage and was dragging other battery down. I replaced both, but because 1 was still good, I kept it and used an older battery I had as a core exchange. Always replace in pairs if possible.

 

Terminals are clean. On second thought I do not think it is a short in the battery as when the other was disconnected I still had the problem with the drivers side. I do agree both batteries need to be changed at the same time. When I unhook the lead that goes to the passenger battery what else is disconnected from the electrical system? The alternator and grid heater? Is that all?

 

Started the truck checked voltage at the cable going to the passenger battery. Got 80 volts. From what I see this is a alternator issue? Or is there a voltage regulator somewhere?

 

Not only the connections, but also the crossover cable between the batteries in our trucks MUST b e checked for continuity and resistance. For some reason, they are susceptible to corrosion UNDERNEATH the insulation, a few inches back from the battery terminals. I have read more then several threads where it has been the cause of the PS battery boiling over and/or exploding. Cut back the insulation from each end and inspect closely for corrosion. If OK, double check for resistance with a quality VOM. If much more then zero, then there is a problem.

All that being said, it might also be a problem with the dcm, but check the cable first.,

Blowing tops of batteries off and over charging - Dodge Cummins Diesel Forum

 

Thanks seafish will check tomorrow

 

Always replace in pairs!!
These trucks monitor voltage from the driverside battery. If this battery is bad or the cable connecting the two has a high resistance the alt will increase voltage. The alt is connected to the passenger side battery so it will over charge and boil. (Or burst)
I suggest to replace both batteries and check or replace the crossover cable and then check voltage at both to see what you are getting.

 

As mentioned, the most likely cause is resistance between the two batteries. This may be at the terminals, crossover cable, or ground side. The issue is that the alternator is hooked directly to one battery, while the charge voltage is monitored at the other battery. This works fine as long as there is no resistance between the two batteries. Once resistance exists between the two, the voltage regulator will keep ramping up the alternator output because it does not see the increase at the other side. Eventually you will see one battery boiled dry, and the other dead.

 

Thanks guys going to check my connections and cables in the morning. If I have 80 volts at the drivers side end of the crossover cable I can be sure that the cable is ok correct?

 

NOT really CORRECT.
If the end of the cable is not connected to a load (battery), there is no current flow and hence no voltage drop.
80V might be the open circuit voltage of the alternator.
Even if you have Mohm resistance on the cable you would still read 80V at the open end.
Load test both batteries to make sure they are good.
Connect everything together and check voltage on both batteries on their own posts, between the center of the positive post and the center of the negative post.
Both batteries should have the SAME reading, around 14.7-15V, depending on ambient temp.

 

Assuming you alternator outputs 100A and each battery takes 50A charging current. A 0.1 ohm resistance between the two battery positive posts would create a 50 x 0.1 = 5 V votage difference between the two battery positive posts.
If the driver side has 11V then the passenger side would have 16V and smoke.

 

Some of the most common issues for this is the battery temp sensor under the drivers side battery failing or the crossover cable between the two battery's failing.

Dirty connections as already stated cause this as well and the wires will corrode under the sheathing where you can not see it. Don't simply focus on the battery cables themselves if you do not find it right away...the wires on the alternator itself have also been known to corrode in the same manner.

The way the system works is the charging system feeds the passenger battery which in turn feeds the drivers side battery via the crossover cable. The charging system via the ECM determines how much charge to send to the batteries via the temp sensor under the drivers side battery.

If the system thinks the drivers side battery needs charging the extra current flows through the passenger side battery cooking it essentially if there is a fault as I already mentioned. A bad cell in a battery can also cause this issue as well which is why it is wise to charge and load test both battery's before getting too deep into the diagnosis.

Every other responder has been spot on with their comments and I hope this simplified explanation of how the system works helps you locate the problem.

 

Perfect will check