ESS Battery cable arcing.

[Jimmyzjeep]

Hello, First time posting.
2020 Jeep Wrangler 3.6l, 4 door.
21k miles.

I winter in Arizona 6 mo’s a year and just arrived to a dead battery. Brand new main battery replaced 6 months ago.
Main battery was reading 5v as was the ESS battery. I had a battery tender plugged into it for the last 6 months but noticed it had failed at sometime.
I charged the main battery back up and jeep started right up.
Then the ESS message to take to dealer popped up. So I disconnected the neg ESS battery cable from the main and charged it over night. It charged right up to 12.8v.
Here’s my concern, when I went to install the ESS negative back to the main battery negative, it thru some pretty sparks. Not just a small arc from a drain, but I could have done some welding with it.
So I disconnected overnight and reconnected this morning without any arcing??
Any ideas what could have caused this besides the obvious of shorting it out by mistake?
It was a simple cable off/on.
Bottom line, jeep runs fine today, running voltage is 14.1v. Everything seems fine with the exception that I lost my Off Road pages icon. (Hoping it will magically reappear after a few starts).
My first thought was the ESS battery may have been bad after all. But it charges right up.
Just curious if anyone else has experienced anything like this.
And to answer everyone’s first question, no I did not replace both batteries at the same time. The ESS battery was replaced approx 18 months ago by previous owner.
Thx in advance for any comments!
Happy Jeeping!!

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[Reinen]

The root cause of the problem is obviously the battery charger failure. A JL can't sit idle for that long without a working charger connected. Batteries at 5v would be expected after sitting idle for 5-6 months.

The arcing is likely because the Aux battery was very drained and fresh off the charger. Lead-acid batteries work through a chemical process that isn't necessarily immediate or even between the battery's cells. Especially after being drained that low and freshly recharged. You likely had some cells that were charged unevenly, some very ready to give off energy while others not so much. Sitting overnight would give all cells within the battery time to chemically balance with each other.

All in all I wouldn't worry about the arcing. It was obviously temporary and a result of the major drain/recharge event. Just monitor the state the batteries are in now. This event definitely reduced the lifespan of the batteries. The question is by how much and are they still reasonably functional.

 

[Jimmyzjeep]

The root cause of the problem is obviously the battery charger failure. A JL can't sit idle for that long without a working charger connected. Batteries at 5v would be expected after sitting idle for 5-6 months.

The arcing is likely because the Aux battery was very drained and fresh off the charger. Lead-acid batteries work through a chemical process that isn't necessarily immediate or even between the battery's cells. Especially after being drained that low and freshly recharged. You likely had some cells that were charged unevenly, some very ready to give off energy while others not so much. Sitting overnight would give all cells within the battery time to chemically balance with each other.

All in all I wouldn't worry about the arcing. It was obviously temporary and a result of the major drain/recharge event. Just monitor the state the batteries are in now. This event definitely reduced the lifespan of the batteries. The question is by how much and are they still reasonably functional.
[/QUOT

The root cause of the problem is obviously the battery charger failure. A JL can't sit idle for that long without a working charger connected. Batteries at 5v would be expected after sitting idle for 5-6 months.

The arcing is likely because the Aux battery was very drained and fresh off the charger. Lead-acid batteries work through a chemical process that isn't necessarily immediate or even between the battery's cells. Especially after being drained that low and freshly recharged. You likely had some cells that were charged unevenly, some very ready to give off energy while others not so much. Sitting overnight would give all cells within the battery time to chemically balance with each other.

All in all I wouldn't worry about the arcing. It was obviously temporary and a result of the major drain/recharge event. Just monitor the state the batteries are in now. This event definitely reduced the lifespan of the batteries. The question is by how much and are they still reasonably functional.

I think you are spot on. It caught me off guard when I tried to hook it back up. It wasn’t a little parasitic spark. I thought I had accidentally hooked it backwards at first but quickly realized it was correct.
Bottom line, jeep is running great now. Running voltage is 14.1.
Thanks for the input, much appreciated.

 

[Jebiruph]

This has been discussed before, these jeeps seem to have unusual arching/sparks when the first battery is reconnected after both batteries have been disconnected.

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