Melted Battery Terminal

[kohldad]

Was driving along the Blue Ridge Parkway in Virginia when the "Check Guages" came on. Noticed that the voltage indicator was not reading anything. After about two more miles, finally found a place I could pull over to check. Upon first inspection, thought the battery terminal where the bolt goes through had corroded in half allowing the relay feed and alternator feed to come loose. Surprised I had missed such bad corrision, but figured no problem, drop down to town and replace.

Make it down to Mt Airy, NC, 22 miles later and find an auto parts store. Grab a replacement terminal and borrow a hacksaw. Only then when I opened the hood, did I notice it had not corroded off like I thought, but had melted. Right where the bolt goes through. The heat also melted a hole in the top of the battery.

With volt meter, I checked the batteries and both still measured 12. 5V so knew neither was shorted. Then I held the alternator feed to the battery terminal and post while my wife cranked up the truck. Voltage, within a few seconds climbed right past 14. 2V and continued to climb past 17V. This is where I released the alternator feed and turned off the truck.

Drove over to the nearby Dodge dealership to let them work on it. But after talking to the mechanic, I felt like it was going to be $250 plus next day before they could start diagnosing the problem. Then figures another day for more parts. By the time they had things fixed, figured my vacation time would be over and I would be out $1k. So wife and I decided to drive home on the batteries, restopping for a night on the way so the camper converter could recharge the batteries.

Next day after making it home without more problems, I started looking for shorted, broken, or fried wires and didn't find anything. I checked all the wires to the alternator and the PCM on the engine block. They all looked good and tight. Decided to check the voltage again and to my surprise, voltage came up to the correct 14. 2V and stopped. Let the truck run for about 10 minutes keeping a close eye on things before shutting it down. Repeated this process severalt times through out the day keeping a close eye and the voltage is always accurate. So it seems the problem has vanished as strangely as it disappeared, probably from moving one of the wires.

Best I can figure, the alternator went to max output due to a loss voltage signal back to the PCM. But I'm curious why that didn't throw a code or shut the system down. More surprised is that the fusable link didn't prevent the long term high amperage necessary to melt the lead.

Has this happened to anyone else? And does anyone have any ideas on what caused it to happen?

Right now, I'm nervous about driving the truck until I get an over-voltage alarm to alert me when it happens again. Usually I'm very good about watching the gauges, but maybe I was too distracted this time between watching the road and the fall leaves.

Edit: Forgot to mention that I replaced both batteries last November with new Mopar batteries.

 

[Road Dog]

A loose connection leads to arcing which can generate a lot of heat. In a pinch two 12V batteries in series makes a fine arc welder (some off roaders carry cable and welding rods). A single 12V battery isn't quite enough to melt steel but will melt lead.

 

[seafish]

I think Road Dog is right on this one... . a loose connection at th terminal would not only heat up, but might also "force" the ecm to up the charge on the alternator as it senses the low voltage caused by the loose connection and tries to compensate.

 

[NIsaacs]

I would check the cable full length and make sure it is not shorted out some where. I don't think the alternator output would do that amount of damage.

Nick

 

[kohldad]

The loose connection causing an arc would make sense. How loose would the bolt need to be before it would start arcing? Or would some hidden corrosion on the bolt be enough resistance?

Obviously I cannot tell how tight it was, but know it was not wiggly loose in the battery terminal. I do know the second nut holding the alternator feed was tight to the first nut for the battery terminal. And I know the battery terminal was tightened when I installed the batteries last year. I have not heard of needing to re-check the nuts themself, but do inspect for corrision at each oil change when the hood is open.

If the alternator at 180A doesn't have enough power to cause the problem (though I often weld at only 100A), the only other draw would be the relays for the grid heater (which I haven't hooked back up yet except for testing). Would that be enough?

This was on the first cold morning (38*) of the year for the truck if that makes any difference, but we had been driving for over an hour with a couple of short stops so the engine was at operating temperature and the day had heated up to mid 50s. Last stop had been about 45 minutes earlier.

Just trying to figure this out so I can trust the truck again.

On a seperate note, did find out that you can drive for over 5 hours on the batteries with all accesories off and they still measured 12. 05V with the engine running.

 

[cerberusiam]

Alternator full output will blow up a single battery, it has enough power to do that. Replace the cross over cable with a new one and any of the connections to the clamp. You don't know where the lack of contnuity is in the cables and all it will do is create more problems down the road. The rust on the bolt head is a good indication there is a connection problem to the botl and ultimately to the clamp. You almost have to pull the bolts out and disconnect and scrape all the connections or it will be an issue.

 

[daytona701]

Hi, I'm new to this forum and to Cummins ownership. I have a 2007 6.7 that has the same problem. I got a check gauge on the dash and noticed the volt meter low. I checked the terminals and the positive on the drivers side was melted but not as bad as yours in the picture. I bought the truck used with 50k in July of 13. I cleaned and painted the battery terminals with Vaseline because of some corrosion/buildup on the terminals. This was in early August before a 3000 mile trip to from Mississippi to Colorado and back. The batterys are less than a year old. As a temporary fix I installed a small c clamp on the terminal until the new cable comes in the mail. I think the problem started by not having the battery terminals tight enough.

 

[MLee]

One should clean the terminals as recommended, twice a year to avoid the corrosion problem. and DOUBLE check all the grounds also.