Your battery voltage - truck off and at rest

[ShadowsPapa]

I'm very curious as I prepare to take my own JT in for ABS/TC and ESS issues.
I'm trying to get valid information on these trucks, and these specific batteries and systems. I have found that if I go in with as much solid information as possible, either my own tech experience as a mechanic years ago, or solutions and good info posted by members here, I get more attention and things are resolved more quickly.

So, all that being said:
What is the voltage measured across your main battery posts with engine off.
How long as the truck been sitting since it last was running when you measured that voltage?
If you provided a voltage measurement here - has your truck been "fixed" by the dealer to make ESS work again and that battery charging message to go away?
* Am looking to compare battery voltages on trucks that have been fixed compared to those that have not yet been fixed but have had the "not ready, battery charging" message.

If you went in with ESS (auto stop/start) issues, what was the solution the dealer provided?
(not looking for "it's still not fixed" or that sort of thing - looking for comparitive numbers, what it took to resolve the issues)

Battery voltage - truck off-
How many hours has it been sitting, engine off -
Does ESS function correctly-
Has the dealership worked on the truck to resolve ESS, if so did they replace batteries or reset the IBS-

Mine was driven off and on yesterday morning for a total of at least an hour drive time. During that whole time (about 2-3 hours of shopping and errands), ESS never worked, constantly said battery charging.
Parked the truck about 11 am yesterday.
Today at 8am battery voltage measured with my Fluke is 12.37

A fully charged standard battery is 12.6 - 12.7 fully charged.
AGM seems to run 12.7-12.8 (depending on the sources of the information)
In any case, 12.37 is far from fully charged. Most info says my battery at 12.37 is 60-70% charged.

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[jac04]

12.36 V
2021 Mojave
Sitting for 26 hours.
ESS works fine, but I usually turn it off.
No error messages.
Never been to the dealer for anything.

For reference, just to make sure my multimeter is OK, I just checked my JK, which has a standard lead acid battery. 12.67 V, but it has only been sitting for about an hour.

 

[Glad_he_ate]

12.4 after being off for 20min. Mine has been in many times for Ess. Also had chassis harness replaced. Aux battery replace and several “updates” to the ecm/bcm. My tc/abs/service 4x4system issue was linked to a bad chassis wiring harness. No problems sense having that done.

 

[Mac]

12.75 volts, been sitting for about an hour since I last drove it. Has not been back to the dealer since I got it.
My plan if start getting start stop errors at some point is to just replace the batteries myself at my own cost, don't have the time or patience to deal with dealer BS. My JT is 1.5 years old and has 26k miles.

 

[ShadowsPapa]

I checked mine again before taking it in - when I opened the hood it came up as 12.19 and then after a couple of minutes, it crept up to 12.25.
Apparently there's more load on things when the hood is closed, or else the thing is acting goofy.
The Fluke is accurate and matches two other digital VOMs I have.
The dealership is 30 minutes away - the entire drive it said auto stop/start not ready battery charging.

There's something really fishy if these Jeep batteries aren't reading a full charge after driving them a bit.

 

[jebiruph]

JT Sport parked for 2.5 hrs - 12.45v
JL Sport parked for 24 hrs - 12.42v

 

[ShadowsPapa]

Looks to me like none of these are ever getting a full charge! That leads to really short battery life in the long run (or short run in this case)
Looks like the vehicle isn't even fully charging the battery to begin with, and then it's dropping 20% or more of it's charge sitting 2+ hours?
That's crazy.

 

[Beemer533]

Well, I just went out and checked mine and it is at 12.29v (on a Fluke 179).

I have 21 Mojave.

It's been sitting about 28 hours after a 30 minute round trip yesterday.

I think it was January when I was away on a week long work trip and when I got back it was dead..

The dealer replaced the main battery and IBS cable (wouldn't tighten properly). I asked and was told that the Aux battery was fine.

About a month ago the same thing happened and they replaced the Aux battery....

As of my drive yesterday, there were no ESS errors (I have it disabled with a Tazer)

The only thing aftermarket I have is the IA Jl3001 and a Tazer, which when I brought it in for the 2nd time they pointed out that that could be an issue.

When they called me back a couple days later, they said that the Aux battery was definitely bad and they made no mention of the head unit...

My plan is to eventually upgrade the main battery to the largest that will fit and eliminate the Aux battery.


Good luck, hope this helps!

 

[Beemer533]

Looks to me like none of these are ever getting a full charge! That leads to really short battery life in the long run (or short run in this case)
Looks like the vehicle isn't even fully charging the battery to begin with, and then it's dropping 20% or more of it's charge sitting 2+ hours?
That's crazy.

Reading this table is kind of worrying to me. I've been traveling for work since 2000 and I am nearly constantly gone. I think my average annual mileage for the last 10 years has been about 5k/yr.

I've been leasing a new car every couple of years (until this jeep) since 2010 and I've never had an issue starting anything when I came home until this jeep.

The thought of having to use a maintainer seems rediculous to me on a brand new vehicle, but I may need to resort to that.

 

[ShadowsPapa]

It's absolutely crazy to think that Jeep accepts a battery at 60-70% charged as being ok, and that it will last, or that it's ok for a truck to have a battery that won't start the vehicle after only a week. These should be able to sit for a month and still start.

Anyone can Google words like AGM battery percentage of charge or AGM battery charge chart or words to that effect. There are variations in part to the different battery brands and the sources - it's not like conventional wet lead acid batteries where the numbers have been known and accepted for 50 years (or more) but the bottom line is these are sitting with a battery only sort of charged. I should be able to drive this truck, park it, open the hood and find the batteries at 12.6+ volts, no excuse, no exception. If it's not happening then the batteries are not accepting a charge or Jeep has something in the circuit that is preventing full charge.
These alternators are kicking out a voltage more than capable of fully charging a battery.

The optimal absorption voltages for AGM batteries are between 14.2V and 14.9V.
The actual charging voltage for the bulk of the work is lower than that.
Float voltages specified for 12V AGM batteries are between 13.2V and 13.8V (that's maintenance voltages)

 

[u-joint]

Mine has been parked since mid-afternoon Sunday. I'll go measure it tomorrow and give you a number.

 

[Mr._Bill]

I have not had any ESS or battery issues with my Overland. It still has both original batteries, which are now about three years old. I have a voltage display unit in the cab that shows the main battery and the third battery that I have installed. The main battery usually reads 12.3 volts when the truck is off, and 14.6 when it is running. After the truck has run long enough (several hours) it drops down around 13.7 volts while on.

 

[ShadowsPapa]

The main battery usually reads 12.3 volts when the truck is off

Which I find interesting as if these were any other batteries or vehicles, I'd be trying to figure out why the batteries never fully charge with the system voltage running over 14 volts while running. Mine runs 14.5 and higher much of the time, that's well into the rage to fully top off an AGM battery.
And while it cranks and works fine even when it's 0 outside, 12.3 is not a fully charged battery.
When searching using Bing or Google and looking for things like "what is the voltage of a fully charged AGM battery" you always get 12.6 or better and even thought SoC charts don't agree on exact numbers, they all agree - 12.4 or less is only partially charged, the best chart saying 75% while the worst saying 60% charged at 12.3 volts.

So, automotive EEs here - what's up with this? I can go to my cars any time and find the batteries even after sitting 2 to 4 weeks have a charge of over 12.5 volts and those start out at 12.6 while a full AGM starts out higher.

In short - why aren't Jeep vehicles fully charging AGM batteries, or, are all of the battery companies - those that MAKE and sell AGM batteries, full of bunk when they say that 12.4 isn't fully charged?
Someone is not telling the truth.

In any case, my ESS only works when the truck is driven for hours, or I charge the batteries overnight, otherwise, the batteries sit at 12.3 volts or LESS and the ESS doesn't work with a battery charging message.

And this shows the voltage with the battery under a load ->
So one could explain a measure of 12.5 volts at the terminals away if there's a fair draw on the battery at the time. It would still be 100% charged IF there was a load like shown here - but mine measured 12.25 volts (and less) so even assuming there's a discharge on it to keep the truck in listen mode, it's still only 80% charged!

 

[Mac]

Just checked mine again after getting a reading of 12.75 v last night, I tried with a second meter this morning and got 12.8 v, this after being off for 2 hours or so, checked again with the original meter and read 12.78 v. Strange it reads higher than most.

 

[ShadowsPapa]

Just checked mine again after getting a reading of 12.75 v last night, I tried with a second meter this morning and got 12.8 v, this after being off for 2 hours or so, checked again with the original meter and read 12.78 v. Strange it reads higher than most.

Yours reads exactly what it should read and is indicating a fully charged battery/batteries and a working system.
Yours reads spot-on where it should.

Thank you for that - proof that it's possible for them to work correctly.

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