Batteries - let's figure this out.

[Andy29847]

Not IMO - that's low, and anything from 12.4 on down can cause ESS to not work.
Some charts show 12.4 as being 50% or less. You consider that good? That's actually pretty bad in my training. Look at this - even 12.5 is RECHARGE RECOMMENDED and you suggest it's acceptable.

From a STAR training bulletin, part of their chart showing when ESS will work -

so if you are at only 60%, then ESS won't activate. Hmmm, that's around 12.4 volts give or take.

Thanks for your input. You were critical of the first tech that worked on my Jeep. I agree with you. Funny to me is the 3rd visit, the one where I was supposed to get a level 3 tech, the paperwork shows the same guy.

I did some charging and testing at home before I took the Jeep to the dealer. What I found was that the batteries would measure 12.7 after 3 hours. The next morning they would be back at 12.4.

My "generalizations" were presented as the conclusions of my recent Jeep experience. I didn't intend to present them a the "answer." Naturally, if both batteries are bad, the Jeep would not start.

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[ShadowsPapa]

Thanks for your input. You were critical of the first tech that worked on my Jeep. I agree with you. Funny to me is the 3rd visit, the one where I was supposed to get a level 3 tech, the paperwork shows the same guy.

I did some charging and testing at home before I took the Jeep to the dealer. What I found was that the batteries would measure 12.7 after 3 hours. The next morning they would be back at 12.4.

My "generalizations" were presented as the conclusions of my recent Jeep experience. I didn't intend to present them a the "answer." Naturally, if both batteries are bad, the Jeep would not start.

The first guy that worked on your Jeep was obviously not up on how to diagnose..... and hadn't read the training documents.

Ironically, these seem to be a tad inconsistent (LOL - the guys and gals here will get a kick out of that) because although it states that 65% is the threshold for ESS, it will sometimes work even less than that.
I've found that with age, these batteries don't "stay up" very well with the load that is present when the vehicle is turned off and parked. It shouldn't be much of a load at all, but after 2 to 3 years (of course will vary with the battery's use and life experiences) they can go from "fully charged" to 12.5 in just a few hours.

I have yet to dig into my 2022 which has a physically larger battery for the crank battery than my 2020 did, and see what the BCM is told it has for amp hour battery capacity. It's all in there, it's all plugged into the settings from the factory - battery type, battery capacity and more.
(aux switches from the factory get you a slightly larger battery)
And even more strange - the setting for shutting things down and killing the electrics appears to have been 8 volts on my 2020 - but 8 volts is a very very dead vehicle, too late.

My 2022 voltage during an ESS event stays up there pretty well - starts higher, and doesn't drop as fast as my 2020 did in later months. Another clue that the battery lost capacity with time - same truck, but the aux battery lost it's capacity the 2+ year mark.
I'd say the same for the crank battery because - well, see my thread something like battery voltage, etc.

Back on the techs - when one tells you your winch is draining your batteries, it's time for that tech to go to some very basic classes and learn about on/off or spst switches.
They are also clueless as to what cables go where when they move a winch ground cable from one end of a ground cable to the other end of a ground cable and say there, we fixed it for you. Uh, it's still connected to the top of the IBS and thus the batteries - how does moving it from one ground stud to another fix it?
Yeah, I have little faith in most of them as far as electric. I've had great luck with 'em in other areas. but electric appears to confuse or elude them. (but then one told me that Jeep ABS doesn't work below 35 mph, either - HUH?)