Start stop not ready / battery charging message after aux battery change - What next?

[ATX_Jeeper]

There is a multi-page document they MUST follow to check batteries - and replace under warranty. I chatted with the guys at a dealership about it yesterday while waiting for other stuff. The dealer gets charged back labor and parts if they simply replace a battery - they EAT it.
If it's below a certain voltage, they must charge it until it is above that voltage. (and at least so many minutes)
Then they must use a very specific type of test equipment to test the battery, they have to scan the bar code on the battery and their tester must be connected via wifi to FCA during the test so the results are transmitted live to FCA. They've had too many batteries replaced that just were not bad.
I believe they told me the batteries now cost $300 each.

Seems excessive but it is what it is. I just hope its actually the battery and not something else as I will have them check 4 other things that will probably need to be covered by warranty.

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[ATX_Jeeper]

For anyone following along, I ended up replacing the main battery on my own and after driving for about 5 miles the Start Stop system started working again.

 

[rr11]

Good to know. I know the battery change is in my near future.

 

[JeepCode4]

I think the question i have after all these posts about the in line battery wiring and their reliance on eachother for the ESS to funciton is.

Why are we replacing batteries after 2 years, less in some cases. Batteries should last double that period and have always in my experience of many vehicles. Are we not driving them, letting them die etc?

I suppose the Forum TSB is, if one goes bad, replace both, but first charge both before installing.

 

[Andy29847]

Why are we replacing batteries after 2 years, less in some cases. Batteries should last double that period and have always in my experience of many vehicles. Are we not driving them, letting them die etc?

I believe the design of the battery system is the culprit. The stop/start quits working when the battery voltage is ~12.4. 12.4 is still a good battery in most applications.

 

[JeepCode4]

I believe the design of the battery system is the culprit. The stop/start quits working when the battery voltage is ~12.4. 12.4 is still a good battery in most applications.

even down to 12 should still be fine in rare circumstances, like lack of usage, not age or dead batt.

 

[scotticus]

For anyone following along, I ended up replacing the main battery on my own and after driving for about 5 miles the Start Stop system started working again.

Same thing happened to me last week! I ended up getting a main battery with slightly more chooch too, 85AH as opposed to the stock 75. Start stop works great now.

 

[ATX_Jeeper]

I think the question i have after all these posts about the in line battery wiring and their reliance on eachother for the ESS to funciton is.

Why are we replacing batteries after 2 years, less in some cases. Batteries should last double that period and have always in my experience of many vehicles. Are we not driving them, letting them die etc?

I suppose the Forum TSB is, if one goes bad, replace both, but first charge both before installing.

I bought my JT used. Its a 2021 and had 18k miles on it so I have no idea about battery care and maintenance.

I initially just replaced the aux with an O'Reillys house brand AGM but that didn't fix my issue. Then I charged my main with a battery tender and that worked for like a day. At that point I knew it was the main battery that needed to be replaced and was hoping to get the dealer to do it but didn't want to leave the JT with them.

From all the threads here and on the JL forum it appears Jeep used cheap batteries. When I replaced the main I went with a DieHard and upgraded to the H7 size hoping it would last longer. I did this because it was an exact fit and came stock in some of the other JL / JT models according to this THREAD on the JL Forums.

 

[ATX_Jeeper]

I believe the design of the battery system is the culprit. The stop/start quits working when the battery voltage is ~12.4. 12.4 is still a good battery in most applications.

Mine was always at 14 volts and the ESS never worked. Apparently this is the charging voltage so it must have logic to disable ESS when this is happening.

 

[scotticus]

I used an H7 (85AH, 850CCA) Walmart premium battery. logic was, 4 year warranty, walmarts are everywhere. But that fixed my start/stop issue. i almost replaced the aux battery, but was just trying not to be stranded. The main battery was getting weak on starts, voltage right after turning on (not starting) was <12v.

 

[ecidiego]

My ESS works when voltage is 14.4 or lower. Only times it doesn't is 14.5 - 14.7. I rarely see the battery disconnected from the alt - no trips long enough.

 

[Lunentucker]

I used an H7 (85AH, 850CCA) Walmart premium battery. logic was, 4 year warranty, walmarts are everywhere. But that fixed my start/stop issue. i almost replaced the aux battery, but was just trying not to be stranded. The main battery was getting weak on starts, voltage right after turning on (not starting) was <12v.

If you left the AUX battery connected it can start draining the main if it's unable to hold a charge.

 

[Andy29847]

even down to 12 should still be fine in rare circumstances, like lack of usage, not age or dead batt.

The batteries still work, i.e., start the truck. It's the trucks sensors that decided the batteries are too low to use the start/stop feature.

FWIW, I have 2 2020 Jeeps, a JT and a JLU. The JLU has the most miles. At 35,000 miles and 33 months, the JLU started showing stop/start not working/battery charging. Three visits to the dealer later, they replaced the main battery. Since then, the stop/start has worked as advertised. The measured voltage of the "bad" main battery was 12.4.

One of my Jeeps is now running with just one battery. The aux battery has been disconnected. The other jeep is still working with both batteries.

Mine was always at 14 volts and the ESS never worked. Apparently this is the charging voltage so it must have logic to disable ESS when this is happening.

Testing for true battery voltage requires the battery be disconnected from any load, fully charged, and allowed to sit for 12-24 hours to bleed off surface charge. A new battery should measure 12.8 bolts in this test. As the battery ages, which is mostly about discharge/charge cycles, the true voltage goes down. 12.4 shows as 50-60% life on the charts I have looked at.

In my experience, charging voltage is normally in the 13.4 - 14.4 range. The charging voltage varies according to the load - load including both vehicle demands and battery needs.

Jeeps charging system is more sophisticated that the systems I have seen in other vehicles. The extra battery, the intelligent battery sensor, and the power control relay are new to me. Also, the digital voltmeter gives precise info that I am not used to having. I am still trying to collect my thoughts on how the voltmeter info can be best used.

My 2 Jeeps are not daily drivers. Generally, the JLU get driven 3-4 times a week and the JT is only drive once a week. My trip are normally short. This is a scenario where the vehicles are not running enough to keep the batteries charged. On these trips, the voltmeter reads 14.6-14.7 all the time.

My JLU has a new main battery. When the aux battery (3 years old) was hooked up, the voltmeter always showed 14.5 - 14.7, even on long trips. When I unhooked the aux battery, the voltmeter started behaving more like I expected. The voltmeter would stay at 14.7 for 20-30 minutes and then the charging voltage would drop over the next hour to 13.9-14.0. From this I gleaned that the aux battery was affecting the behavior of the charging system. It is a good battery, but too old to be paired with a new battery.

My JT still has both batteries (still in warranty). On start, it charges at 14.7. If I drive it long enough, the charge voltage goes down to 14.3-14.4. This tells me my batteries are good, but they are old.

When the warranty expires on my JT,I will disconnect the aux battery. When I have to replace the main battery on either vehicle, I will buy a high grade group 94/H7 battery. I see no reason to continue with 2 batteries. I plan to delay removing the aux battery and associated parts until I have a reason to remove the parts that have to come off to access the battery system pieces.

 

[chorky]

Testing for true battery voltage requires the battery be disconnected from any load, fully charged, and allowed to sit for 12-24 hours to bleed off surface charge. A new battery should measure 12.8 bolts in this test. As the battery ages, which is mostly about discharge/charge cycles, the true voltage goes down. 12.4 shows as 50-60% life on the charts I have looked at.

Agreed. 12.4 is too low. 12.0 is far too low. To keep a AGM battery in optimum condition and not have significant reduction in lifecycles it should stay above 70% SOC (About 12.3v) They can go below for a time but consistently doing so reduces their lifecycle.

I confirmed this after talking with several battery manufacturers.

‘can’ a battery function at 50% SOC. Sure. Is it good or optimum. No way. And for a factory system a indication of problems

 

[Jeeperjamie]

I think the question i have after all these posts about the in line battery wiring and their reliance on eachother for the ESS to funciton is.

Why are we replacing batteries after 2 years, less in some cases. Batteries should last double that period and have always in my experience of many vehicles. Are we not driving them, letting them die etc?

I suppose the Forum TSB is, if one goes bad, replace both, but first charge both before installing.

Depends on how much your driving it. I've got 70,000 miles on mine in 3yrs, I had 52,000 when my main battery went out but I also have jumped about 4 or 5 vehicles off with my jeep in the first 52,000 miles.

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