AUTO START/STOP BATTERY ISSUE

[Nova _Nish]

Hi All,

I have a 2019 Jeep Wrangler Rubicon that I bought used in 2022 at around 45k miles.

I replaced the main battery a few months ago after a hard winter, but had issues with the new one keeping a charge twice now every 4 weeks. I needed a jump on that same new battery yesterday as it was sitting at 9 volts when I looked at the dash. I took it back to AutoZone for a warranty replacement since the last diagnostic test I got there said the alternator and starter were fine, but the battery was not holding charge and nothing else was noted by them. There's no check engine light or any other indicator as to what could lead to a issue. I see that most are mentioning the aux battery being an issue; however, the warning for this battery to be serviced has always been on and I never used the feature. I assumed the previous owner disabled it since some work was done on it. I've never had issues until now since I replaced the old battery, so I'm hoping the new warranty replacement battery holds up but I don't want to be unprepared if it doesn't. My question is if I manually turn off the auto/start stop feature using the button on the dash, will it still drain the main battery and even if the aux may be dead? I was debating on performing the aux battery solution of removing the 40 fuse and battery cable from the main battery, but I'm also just wanting to have someone replace the aux and be done with it unless disabling it with the dash button works.

Any help and advice much appreciated!

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[ScotM]

If the aux is not disconnected from the main battery, it will kill the main. You must remove the negative aux ground from the main battery, wrap it in tape and zip tie it out of the way. Then remove fuse 42. There are plenty of videoed showing how to do this, I think assuming that the previous owner did something is a mistake. You need to verify any work that was done.

 

[Heimkehr]

Per post #2.

It matters not if the vehicle's ESS function isn't used. Unless and until the smaller battery is electrically isolated from the main battery, the former will eventually parasatize the latter. That seems to be what's occurring here. With that in mind, it's possible that the recent warranty replacement of the main battery was avoidable.

 

[Nova _Nish]

If the aux is not disconnected from the main battery, it will kill the main. You must remove the negative aux ground from the main battery, wrap it in tape and zip tie it out of the way. Then remove fuse 42. There are plenty of videoed showing how to do this, I think assuming that the previous owner did something is a mistake. You need to verify any work that was done.

Really appreciate the help! I'm going to do this after looking at some videos. I shouldn't have assumed.

 

[Nova _Nish]

Per post #2.

It matters not if the vehicle's ESS function isn't used. Unless and until the smaller battery is electrically isolated from the main battery, the former will eventually parasatize the latter. That seems to be what's occurring here. With that in mind, it's possible that the recent warranty replacement of the main battery was avoidable.

Really appreciate the assistance! I shouldn't have assumed that the bypass was already done since I didn't have any issues with it before. I saw a few comments saying they just disable it with the button and things are fine. I'm hoping that the bypass will save the new battery.

 

[ScotM]

Really appreciate the help! I'm going to do this after looking at some videos. I shouldn't have assumed.

Feel free to DM me if you run into any snags

 

[Nova _Nish]

Feel free to DM me if you run into any snags

Will do! I really do appreciate the extra assistance. I'll have a few questions based on some vids I've been watching once I get it completed when I'm back home.

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