2021 main battery replaced under warranty 24k miles

[TTU03]

Truck would not start this morning. I jumped it and drove the dealership. Dealership put the aux battery through a load test and it passed. The main battery tested second and it did not pass. A new main battery was installed. I wish they would replace both with all of the aux battery issues I read about. But glad at least one came back bad vs being told they are fine and just need a charge. No dash warning lights to give me any idea I was having a battery issue.
Also I really like the service guys at my dealership. I know a lot of people despise dealerships but this is one of the good ones I feel.

Sponsored

 

[Andy29847]

A lot of the "aux battery bad" noise is not true. My main battery went bad first too. Like you, I was concerned about pairing an older battery with a new one. My warranty ran out a month after they replaced the battery. When the warranty expired, I disconnect the old aux battery. Disconnecting the aux battery takes out a lot of the mystery of the Jeep battery/charging system. The voltmeter on the dash now accurately reflects the state of my battery. Most important to me, the vehicle should behave like the others I have driven for the last 50 years.

 

[Mr._Bill]

Do you really want your modern, computerized vehicle to behave like one from fifty years ago?

 

[Andy29847]

Do you really want your modern, computerized vehicle to behave like one from fifty years ago?

YES! I definitely want one that I don't have to take to the dealer when the batteries get low.

 

[Mr._Bill]

YES! I definitely want one that I don't have to take to the dealer when the batteries get low.

You don't have to take it to the dealer. Battery quality is a crapshoot with Jeep. If the dealer replaces a failed battery with another 'top-quality' OEM unit, the odds of another failure are not in your favor. The battery setup in the Jeep is not the problem, it's the quality of the batteries being installed. Jeep had a run of bad AUX batteries, which helped perpetuate the misinformation about the system. My main battery failed first, with the typical ESS and AUX Switch messages. I replaced it with a good quality 94R battery, and the problems went away. I bought a new Aux Battery at the same time, but have not replaced it yet. The original is four years old and still doing its job.

 

[Andy29847]

I bought a new Aux Battery at the same time, but have not replaced it yet. The original is four years old and still doing its job.

I'm glad your Jeep is trucking along OK. It took 3 visits to the dealer before they replaced my main battery. The battery was good by most standards, but not good enough to pass the Jeep systems poll to enable the stop/start. And while my Jeep worked as designed for 6 weeks after the new main battery was installed, I continued to be concerned about the effects of pairing an old battery with a new battery. One thing that I noticed was that my dash voltmeter always showed 14.6-14.7 volts, i.e., maximum charge. When I disconnected the aux, charging activity for my Jeep started showing a more normal pattern. It would start charging at 14.6 when I first cranked it, and it would drop to 13.9 after ~30 minutes of driving. I viewed the change as evidence that the aux battery was a detrimental presence. I don't know if that is excessive concern on my part, or not.

FWIW, I have 2 2020 Jeeps - a JLU and a JT. One is 6 months older than the other. The oldest is the one that was causing me battery problems. The other has been fine until this morning. It was cold here, 29 degrees. When I got out this morning the Start/Stop never work. It showed battery charging the whole time. I expect the main battery is getting weak on this one too. Both batteries tested in the 12.6 range with my voltmeter, But I would have to let them sit over night to get a good reading. I have disconnect the aux battery, I am charging the main with my AC charger. I plan to drive it like this and see what happens. I expect that the stop/start will not work with just the main battery (because that is the one I think is weak). However it turns out, at least it is something I can test.

 

[Mr._Bill]

The life expectancy of the AGM batteries used in the JT/JL is about three years. The Aux battery should have been replaced with the Main battery. The dealer has a specific process to follow to get approval to replace a battery under warranty. Just because a battery didn't fail the dealer warranty test doesn't mean it is in good condition.

 

[Andy29847]

The dealer has a specific process to follow to get approval to replace a battery under warranty. Just because a battery didn't fail the dealer warranty test doesn't mean it is in good condition.

My point exactly.

 

[bd100]

Might be a good idea to just replace both whenever the aux start/stop no longer works. Better than being stranded.

 

[ShadowsPapa]

Truck would not start this morning. I jumped it and drove the dealership. Dealership put the aux battery through a load test and it passed. The main battery tested second and it did not pass. A new main battery was installed. I wish they would replace both with all of the aux battery issues I read about. But glad at least one came back bad vs being told they are fine and just need a charge. No dash warning lights to give me any idea I was having a battery issue.
Also I really like the service guys at my dealership. I know a lot of people despise dealerships but this is one of the good ones I feel.

Like already said - you need to ignore have the bull crap out there on batteries and electric systems.
Plus - the dealership MUST - and I mean MUST - run a VERY specific test in a specific way using a specific machine and submit the testing - not just the result, but the whole thing must be on wifi and transmitted to Jeep before they can replace a battery under warranty - otherwise the dealer eats it. It also must be charged to a certain state before they can test it - so if you go in with a battery sitting at 12.2 volts, they can't simply test it, they have to charge it for 30 minutes first. So if they tested a dead battery without charging it - they likely are just doing a favor.
The test equipment they use is very expensive, not like the cheap stuff a "parts store" uses (and usually can't understand the results anyway). It's pretty accurate.

Battery life has a lot to do with how often you drive it, and how far/long you drive it when you do.

I expect 2022 and later model years to behave a bit better as far as batteries and ESS. They've changed some things.

Might be a good idea to just replace both whenever the aux start/stop no longer works. Better than being stranded.

Being stranded is also magnified by the internet. The risk is not as high as the "it's the aux battery!"
screamers would have us believe.
They can almost always be jumped - if jumped properly and not impatiently.
ESS not working may have zip to do with batteries. So you'd spend hundreds of dollars to swap 2 batteries that may not be the, or even a, problem? No diagnostics, no troubleshooting?
If I did that, I'd have replaced the batteries on my 2020 instead of simply doing an independent charge of each battery, resetting the IBS and moving on.

 

[bd100]

They've changed some things.
...
They can almost always be jumped - if jumped properly and not impatiently.
...
independent charge of each battery, resetting the IBS and moving on.

Almost nobody knows how to do this, and who wants to wait until it needs jumping, potentially at a bad time/place? I replaced them on my wife's vehicle because they were resting around 11.9 volts, ESS never came on, and I want her to have a reliable vehicle.

Curious to know what has changed for 2022 and up.

 

[bd100]

And it'd be nice if they could have the computer tell us when each of the batteries is getting weak.

Sponsored