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Discussion Starter · #1 ·
First of all thanks in advance for any and all help. I have a 15' 2500 6.7. I will try to include as much info as possible, 3 weeks ago truck wouldn't start. I checked volts on batteries and were all good ( I did not load test them at this time) not knowing my a#@ from my elbow at this time all the truck was doing was a loud click which led me to believe it was the starter. I climbed under and gave the starter a nice wack with the hammer and the truck started right up ( turned out to just be ironic). I replaced the starter thinking that was the problem. Truck worked great for the next few days and then one morning would not start again. I hooked up jump pack and it started right up so I took it to oreilieys and had them test the batteries. One of them had a bad cell and needed replacement so I replaced only that one ( I know a mistake) worked great again for a few days and then one morning had a dead truck again. Jumped it off and drove it to work (about 45 mins) when I got there I started smelling a weird smell, I opened the hood to find the battery I did not replace smoking. I unhooked it and carried it up to autoparts store. They said it had a bad cell now to and needed to be replaced. There explinantion ( the good battery probably caused the older one to overcharge). Well now I had 2 new batteries and thought I was good to go. A few days later trucks dead again. I've checked everything I can think of. Battery voltage at stand still is 12.8. Battery voltage while running is 14.1. Battery voltage coming off alternator is 14.1. Did a parasidic draw test and am only showing .08 miliamps draw after truck sits for 30 mins. I checked resistance bewteen battery cables and tests good. Checked grounds on starter and it's good. I have 14.1v with positive multimeter lead on B post and negative on case of altenator and 0v with it set up the opposite way which from what I read tells me the diodes of altenator are working (or so I think) I'm at a loss of what to test or check next. Any help would be greatly appreciated. Thanks guys
 

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I think one of your new batteries has a defective cell. Just because it is new doesn't guarantee it is good. From my lessons learned book, I bought a new battery that had a single cell that every so often would flip polarity and then flip back. When it flipped, it would stall the engine (gas engine). In order to detect this, I put a voltage monitor on the battery and caught it.
 

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Discussion Starter · #3 ·
Makes sense I need to get something that can measure volts and amp draw over an extended period of time. Went to bed battery voltage was at 12.8. Woke up this morning and it's at 10.6. Not showing much of a amp draw this morning either.
 

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Given the information you shared, if it were me, I would pull the negative cable from each battery. Wait an hour or so, take a voltage reading. Come back the next morning and take another voltage reading from each battery.

This test should expose a bad battery. If not, there may be electronics that are not sleeping causing your drain which is very unlikely but not unheard of.

If you have a DVM that can capture and log minimum and maximum values, you could set that up on a battery and see what it captures. I used a four channel signal logger;

https://www.vellemanstore.com/en/ve...cyGgZ-Uci7RKrSa-DDDpRfUvbdVIyvcxoC7oQQAvD_BwE

For $50 it isn't a bad logger. If you pick up a couple of DC current battery shunts you can use the other two channels to watch current consumption.
 
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