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Discussion Starter · #1 ·
The two batteries in my 2011 Ram 2500 with Cummins Diesel are

Group 94R
Width: 6.94
Length: 12.44
Height: 7.50

I had a hard time finding out this data, and my truck spec sheet incorrectly said the truck used Group 65. There are many discussions here about the best battery BRAND, but none on the size. So there you have it, two from size Group 94R, which you will find is not a Costco-compatible size.

Not to get religious about which brand is best, but I looked at Consumer Reports with my membership there, and while they don't review our Group94R size, the other sizes almost always have the EverStart Maxx Automotive Battery as a top result, let alone one of the best deals. I was surprised to find that this was the brand carried at Walmart. They call the size Group Size H7.

My batteries were ruined when a back AV installer put my MyGig LockPick hack device in incorrectly, and it sucked all kinds of power when the truck is parked for long periods, which it often is.

They are wired in parallel. If you saw batteries, you can do it one at a time, so as not to erase any data in your computers and MyGig. However, if you do, the positive cables will be hot from the other battery, so isolate them with a couple of old socks or work gloves.
 

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Discussion Starter · #2 ·
Correction

In the last paragraph, I say "If you saw batteries". That should be "if you switch batteries".
 

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Discussion Starter · #3 ·
Desulfation

So I bought a battery load tester, which hooks a heater coil to the battery for 10 seconds, and you take a voltage reading with the load.

At first, I tested with the batteries connected to the truck. It tested fine. But since the batteries are in parallel, I didn't know if they were BOTH good. Basically, if you fail this test, then you know both are bad, but if you pass it, you don't know if one is bad.

I disconnected the batteries, and found that one was bad. I pulled that battery out, and have it connected to a desulfator, which may or may not rescue it. I'll report back later if I have success.

If my desulfator fails (it can take up to three weeks to fully work), I'll go to Wally Mart and buy a new one. For now, I'm mostly just playing around to see if I can get lucky with the desulfation.
 
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Discussion Starter · #4 ·
Running Cummins With One Battery

Anyhow, while I'm doing the desulfation test above, I'm running my Cummins on one battery. Given how well this has been going, I would NOT advise it.

If it's warm (over 55 f), or the truck is warm, or it has been run already that day, it starts up. If it is cold, or the truck has been sitting for a couple of days, it will not crank. I have a portable battery jump starter, and that's all it takes for it to start right up, even in the coldest sub-freezing days. This truck needs two batteries to work reliably.
 

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that is very interesting, please keep us informed

:rep:
 

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my experience is if you load test a bad battery, you find out it is now dead. those heater coil testers are not the best. check the voltages at rest after sitting for awhile. 12v-12.3 marginal battery, 12.5 and up , a good battery. also test the specific gravity. your desulphater should help.
 

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Discussion Starter · #7 ·
No Luck With Desulfation

The battery responded to the desulfation a bit in the first couple of days, going from a load tested 5 volts to 7. But it hast stayed at 7 ever since. I suppose I have a bad cell or three. Too bad. I'll go to Walmart, buy an H7, and put her in.

Based on the bubbling I hear from the battery during the entire 2+ weeks of desulfation charging, I think the process works, at least some. But it cannot fix a bad cell. Sorry. Can't offer conclusive opinion on the benefits of desulfation.
 

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I remember seeing a truck show that showed using 1 lithium ion3 battery for a diesel instead of the normal 2 and they had to modify the cabling for 1 battery only and the lithium battery started cold motor with no problem. We also have a micro start xp-10 jump starter and it is lithium and it has started our truck by itself. Never ;leave home without it!
 
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