how do I not get stranded by the AUX (ESS) battery

[Joaquim]

2019 JLUR. Had battery failure - both main and aux - in April, 2022. I completely removed the aux battery, ran the aux positive cable up to the main battery, and disconnected the aux ground from the main battery. One year and 10K miles later I've had zero issues. No warning lights. No stress about getting caught on the side of the road/trail due to a bad aux battery.

I do have a Tazer hooked up that keeps ESS turned off, but I have played with the ESS since removing the aux battery and everything works as it should.

Hm I'm going to have to try this. I went to the dealer to get the PCM updated with TSB 18 092 19 but they said it was already done. Not really sure why it wouldn't start if that TSB was already run...

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[Canucklesammich]

Interesting, because I just spoke to my Dealership Service Dept earlier today. Told them my ESS was not working anymore. They mentioned my Aux Battery was probably at less than 70%. But there's no way to know unless you measure it directly. So, I asked if I am at risk of my Jeep not starting at all, if that battery is close to death or dies soon - and they said "No, I don't believe so. That battery only powers the electronic start." ... but, now I'm not so confident in their response. Guess I need to do some more reading in this forum. They did say I can have it replaced under warranty when it dies, since I'm still covered.

What happens is, as the aux drops in voltage, the Jeep tries to balance the 2 batteries using the main; so as the aux continues to degrade, it pulls the main battery down with it until neither battery is capable of starting the engine. Isolate the aux battery as stated & you eliminate the parasitic draw & save the main.