Low Voltage Fight (searched to death) (1 Viewer)

[montegofd3s]

Hello Fellow Mudders!

I will try to keep this short, but here are the basic problems that I am having....

-During Start up the volts are showing 13.4-13.1
-As soon as an load as put on the system it drops dramatically to 12.0-11.8 (may recover to 12.2 but only occasionally). This is can be when I stop at a red light or whatever. Seems more prevalent when the vehicle is warm. During normal driving down the road it is steady at 13.1ish.

- I changed to a Diehard group 31 exactly 1 year ago.
- I thought it was the alternator/voltage regulator so I changed it....same issues.
- I thought it could be a ground issue so I upgraded the ground wires on the battery and the block...no dice.
- I thought it could have something strange drawing it down from the fridge, amp, or winch so disconnected those....same problem.
- I brought in the battery to Sears and they tested it and said it tested good. I still believe there is a dead cell in the battery or it is sulfated (I don't know if they load test it or what), but I am not sure how to get them to change their synopsis. With nothing running the battery is showing 12.6-12.8v. The truck always starts fine, but I am sure it would even with 5 cells in that big honkin battery functioning ok, plus I drive about 70 miles a day to and from work so it gets a decent charge on the interstate. Even still....this isn't right.

Any thoughts on this issue? Any help would be greatly appreciated.

Thanks,
Josh

 

[n55luvr]

I've had similar happen and I swear it was a bad cell but I could never prove it. In my case I had a battery that was less than a year old. Bought from local car parts store. My truck simply refused to start, like the battery would loose juice over night. Tested for parasitic loss, tested alternator, basically everything you went through. Took back to the store and of course it passed their test.

At that point my only option was new battery that I had to pay for. Truck ran great on the new battery for the next several years, not a single issue. Something was definitely wrong with that battery but again I had no way to prove it.

 

[Ninja Cruiser100]

I would bet money on a bad battery.

 

[Sandroad]

From your searches, you'll know that many have had problems with the DHP 31 batteries. Your description and troubleshooting so far could certainly indicate a failing battery. The store tests are not always reliable for anything but a completely shot battery. Given your situation, I'd swap in another battery before I replaced any other components.

 

[montegofd3s]

^ Indeed. I just didn't know if maybe anyone also had any advice on how to approach the issue with Sears? Can I request a load test or maybe get it tested somewhere else and bring the results there or am I just out of luck? Sucks, but that may seem to be the case here. I just kept hoping that wasn't the issue, and with 230k miles on the odometer I figured the rig could use a new alternator anyway. Always good to get some fresh advice from the mud community on a path forward.

 

[re_guderian]

... Took back to the store and of course it passed their test.

One more reason that Costco batteries rock...

 

[uHu]

Sounds like a bad voltmeter.
Where do you measure these volts? You have to measure directly on the battery pole in order to say anything definite. And that's on the pole, not on the terminal, unless you have checked it for voltage drop under load.

 

[WaterCruiser]

a dead cell usually presents as consistently lower (versus fluctuating) voltage, although a loose plate would cause the voltage to go up & down. if it's due to sulfation (acid stratification) you might take the battery out and simply shake/rock it - if you connect a voltmeter while doing this it will let you know if a plate is loose

how old is the battery?

 

[montegofd3s]

Volt fluctuation can be seen both on the scan gauge while driving (read from ecu), and on the Bosch voltmeter at the battery using multiple points so I am pretty sure that isn't it.

Battery is 12 months olds. It is an AGM so idk if shaking it is going to do the trick for this one sadly....plus it's like 80lbs. Haha

 

[duggy]

I had the same issue with both of my DHPs and I had trouble with Sears saying that the battery was good, even though I kept having issues with both of them. I eventually took it to another Sears in Houston and got them to confirm that it was a bad battery. They swapped me out for a DieHard AGM Gold and refunded me the difference in price and now my charging issues are gone.

 

[dogdaysindurham]

I've been reading up on this issue for a while and after some digging (see Table 3 of the linked technical document from Odyssey/Enersys), so the recommended bulk recharge current for the DHP31M is 40 amps (which is the Odyssey 31M-PC2150) and they suggest a higher voltage bulk charge voltage set point recommendation of 14.7 (at around 70 deg F) (http://www.odysseybattery.com/documents/US-ODY-TM.pdf). They also have a table (#5 I think) which shows to recharge a completed depleted battery to 80% would take 8 hrs at 20 amp rate and 4 hrs at 40 amp rate (extrapolated).

From my 05 100 series factory service manual, the battery charging circuit has a max current of only 30 amps (from Charging Service Specifications, SS-21 but is my interpretation of the listed table value correct?) and a lower bulk charge voltage set point of 14.2 volts (this is based on replacement voltage regulator set point, IN6015 for the 130 amp denso), although the FSM says this can normally range from 13.2 to 14.8. So it could be that the 31M sized battery is only being recharged to 70-80% and never fully recharged. This supposedly over time that will hurt the battery over time.