Truck is a Duramax 6.6 diesel, crew cab 4x4. 78K Miles.
Have owned it for 6 months, No prior issues or indication of any problems.

Yesterday I went to start it, and it acted like weak battery, (it did start, but made a quick stuttering sound, and turned over a bit slower than normal).

As soon as it started, I looked at the dash voltmeter. It was a hair under 14V, (it normally ranges from just under, to just over, the 14V mark).

An hour later, it would not start. No click, the digital dash would go black, and all the gauges drop to the left peg. I turned key off, then back on, and voltage gauge showed approx. 12 volts.

It has dual batteries from the factory, original AC Delco units. Truck is 3 years and 1 month old. I put my multimeter on both batteries. The Auxiliary batt (drivers side front) read 11.93V, the main batt (Pass side rear) was at 12.12 Volts.
If this was a regular, single-battery vehicle, and since the alternator appeared to be putting out adequate voltage, I would tend to think the battery was dying. But the odds of 2 batteries failing on the same day, seem very unlikely. (Unless 1 died and killed the other?). I don't know how the 2 are electrically isolated from each other, but they must be, because the voltage readings are different?

Had a buddy with a tow truck come over and tried to jump it, made no difference at all. Tried on both battery circuits. No crank, not even a solenoid click. He thinks it is the starter, but he is not a GM mechanic. My thoughts are that it is something else, because a bad starter would not cause the batteries to drain while sitting, right?

I went out this morning, and tried it again, same result, but the factory gauge shows lower voltage, (scale not marked between 9-14V).
My voltmeter showed both batteries lower than yesterday: (Aux at 11.72, Main at 11.9). Makes me think there is a short or some kind of load on the electrical system, even with key off. I guess next step is to pull both negative cables, and recheck voltages? Thinking I might try disconnecting cables from both batteries, recheck voltages, then try putting my charger on one battery to see if it will take a charge? And if it does, maybe leave the Aux side disconnected, (in case that side has a short, since it reads lower than the Main batt), and try to start off the Main batt only?

Would really appreciate any guidance or advice from you fellas.

Thanks in advance. -Jim.

Update - I pulled Neg cable from primary battery, and it was still showing 11.7v
Put my charger on it, and it seems to be taking a charge, (10 Amps). Wondering now if the Alternator could be bad. It is a 150 Amp unit, could it be putting out good voltage, but no/low current? I do not have a current probe, my multimeter only has a 10 amp max current rating.
Will these things start on 1 battery? They are rated 730 CCA...

If the alternator is putting out good voltage then the amperage is also there.

With nothing on inside the truck put your ammeter between the negative battery lead and negative terminal and see how much current is flowing. In a perfect world there would be nothing flowing, but with all the electronics in modern stuff you will measure something. Maybe only on one battery, don't know how these things are wired and I have a 2017 version.

Mike, that was my thought also, if voltage is there, current should be as well.
It did take a full charge, reconnected and batteries are at 12.88 & 12.92 volts. Wondering if it could be a dead short in the starter. Tried it again, nothing, but it did drop both batts down almost a 1/10th of a volt after 2 quick attempts.
Anybody changed one of these out? Looks like 2 bolts, bottom one is in a tight location.
(I told you guys last week about my luck - The 12 month/12K mile Certified/Pre-Owned factory warranty ran out about 400 miles ago, 1 week)...

Load test the batteries, individually....



I have a Duramax and replaced the Delco batteries after 7 years.....they were still good.


Put Interstates in it and maybe 2-3 years later while replacing door speakers, truck wont start.


Charged batteries and went to work next day and checked batteries. One was NFG....


Replaced both.....again and did not get much help from Interstate dollar wise.....and we are a big customer.....


Check your Batteries....

Rich, thanks, that will be my next step.
Because the battery voltage drops significantly after a few attempts to start, I think I can rule out any of the common potential issues between the batteries and starter/solenoid. (Ignition switch, anti-theft, Neutral safety switch, relays and fuses).
Would like to check voltage drop when trying to start, but no helpers around...

My 7.3 Powerstroke had a similar issues a few years back. After I ruled out batteries, starter and solenoid, I read some forums about corrosion on the positive battery cable being problematic. Sure enough the positive cable that connects both batteries together was corroded up inside the insulation, not visable until the insulation was peeled back. Replacement from O'reilly and back in business.

Your batterys are tied together with cables , If one gets a bad cell it will take the other with it in most cases. The battery on the pass. side has a cover with a bunch of high amp fuses under it, Check if all connections are tight and clean.

Rich was dead on.
Got a hand held load tester, and one was good for 525 Cranking amps, the other 450-475. (That was after fully charging each one). Spec is 730. They dropped off considerably on a 2nd test. Went to Walmart, got a pair of their Ever Start Maxx units for $119.76 each + tax. 5 year warranty, first 3 years is free replacement, then prorated the next 2.
900 cranking amps. They are both date coded last month, 8/18.
Just got done installing them, fired right up.
Took a minute or so for the alternator to kick on, had me worried at first. Voltmeter read about the same with engine running or off. Restarted it, and needle moved up slowly to just over 14v, so all appears to be good now.
Thanks guys, I appreciate the help and comments.

Sounded like a battery problem to me...

Walmart batteries are the same as Interstate from what I've read but with a different brand name and a better warrantee.

We sell a lot of batteries and use Interstate + one other company.

Tried other suppliers but Interstate batteries generally are better.



In the emergency generator world, batteries sit with automatic chargers on them 24/7 and in a power failure the generator can't start with bad battetries. The batteries are critical.


Batteries get recommended for replacement much sooner than most people would change a vehicle batteries.



They often do exactly what you had happen...…

Show good voltage with a meter but have no ampacity to crank a starter and just click or chatter....

Easy fix.....and Walmart warrantees those for 2 or 3 years full replacement.....

FWIW - I remember hearing somewhere that only 3 companies manufacture batteries in this country - Delphi (makes Delco), Johnson Controls (Interstate & others) and Exide (Die Hard & others). If you go to an Interstate dealers warehouse you will see the Costco & I believe Walmart brand batteries there. I've never been a fan of Exide and the reason that Die Hard batteries quality went away a few years back is because they switched manufacturers from Johnson Controls to Exide. When I worked for a Toyota & Mazda dealer, the Interstate dealer would come in and see what we needed and then either slap a Mazda or a Toyota label on them right on the truck!

We tried a local distributer a few years ago...

Batteries Plus...and it was a family business with 2 locations.

Nice people but batteries were not good.


High failure rate and their big 4D and 8D batteries were total junk....


We went back to Interstate..



Deliveries once a week and I can call and get a special battery delivery usually same day....


I get Optimas from them also if needed....

I heard the same thing that Billy said, (only 3 battery mfrs remaining in the US).
And yes, DieHard's are complete junk now. No wonder they went to a flat 2 year warranty and done, no more pro-rating for 5 years. My last one (bought 5 years ago) died at 2 years, about 3 weeks beyond the warranty date.

Notice how all of the batteries these days are cutting way back on the warranties? O'Reilly used to go 5 years, then 3, now 2 on their Super Start units. (The counterman did tell me they switched from Delphi to Johnson Controls as their source some time ago).
I guess the lone exception is Walmart. I put one in the mother-in-law's 97 T-Bird a few months back. Figured that way she not only has 3 years free swap, but there are W stores everywhere.

Most Batteries Plus batteries are Deka's.

quote:

Originally posted by FootbrakeJim:
I heard the same thing that Billy said, (only 3 battery mfrs remaining in the US).
And yes, DieHard's are complete junk now. No wonder they went to a flat 2 year warranty and done, no more pro-rating for 5 years. My last one (bought 5 years ago) died at 2 years, about 3 weeks beyond the warranty date.

Notice how all of the batteries these days are cutting way back on the warranties? O'Reilly used to go 5 years, then 3, now 2 on their Super Start units. (The counterman did tell me they switched from Delphi to Johnson Controls as their source some time ago).
I guess the lone exception is Walmart. I put one in the mother-in-law's 97 T-Bird a few months back. Figured that way she not only has 3 years free swap, but there are W stores everywhere.

My friend just got a battery from Honda for his mini van. He claims it has a 100 month warranty!? I wasn't going to argue but i can't imagine anyone warrantying a battery for 100 months.

quote:

Originally posted by T172JR:

My friend just got a battery from Honda for his mini van. He claims it has a 100 month warranty!? I wasn't going to argue but i can't imagine anyone warrantying a battery for 100 months.[/QUOTE]

They are but its pro-rated down to like 5% - if his battery dies after 7 years he'd be lucky to get $10 off!

quote:

Originally posted by T172JR:
Most Batteries Plus batteries are Deka's.

Deka's are made by East Penn. They are the best IMO.

^^^ i agree ^^^

No battery lasted better than Delco's in my experience.

Miller welders come with batteries with their Name and Labeling on them.

They also last longer than just about any other battery. I've seen them still going at 6-7 years and that's unusal for a piece of equipment that is not used all the time and the batteries are neglected.

I don't know who makes them but it was not possible to get an exact size replacement for one in particular used in diesel Trailbazers.

The Batteries Plus 4D and 8D batteries failed so badly we dropped the company.

They even sent a rep here with the distributer to apologize and say they knew those batteries were a problem and were fixing it.

Those are large truck type batteries and we rely on those for any large generator. Usually used in pairs.....12 or 24 volt.....

With thousands of machines that my place PM's and is responsible for to run in a power failure, we're using what has been the most reliable.....Interstate...


We have had other companies supply us with batteries as well....


If Deka made Batteries Plus batteries that does not speak well for Deka to me....


I never felt they were very good....

i only deal with their small batteries that come in power equipment and maybe a few car batteries a year. I think Napa batteries are Deka also. The Deka rep cam in with the Batteries Plus owner and basically said we don't want to deal with the outdoor power equipment industry anymore so we are handing everything over to Batteries Plus. In 30 yrs of being at our small shop i have never had a bad Deka battery but i only sell a 100 -150 batteries a year. i also have sold Interstate and only warrantied 1 car battery ever. Interstate won't come close on price and cater to bigger shops who prob do 500 plus batteries a year to get better pricing. Exide and Yuasa and two companies that are horrible and i rarely see one last more than one year in power equipment. We don't do anything heavy duty so i don't use big batteries.

Everyone has different experiences. I just got new truck tires. Bridgestone Duravis M700. I called around and everyone asked why would i want Bridgestones? I just got 40k easily on a 4x4 work truck that pulls a trailer and they wore perfectly and i could have gotten another 5k miles out of them. They worked for me so why cghange was my thought. Finally a guy said put on whatever you want and i bought them.