Aux battery failure after one year?

[humpndunk]

I have a 2018 JLU that I bought one year ago, October 2020. The ESS warning light on the dash has been on for 6 months, and I finally got around to ordering a replacement aux battery and the clips to reinstall the fender flare, and yesterday I dug in to do the job. Pulled the old battery out (a Mopar), and immediately noticed a sticker on the side that said "Shipped Sept 2020." So this is not the original battery that was due to be replaced at the 3-year mark, but instead a one-year old battery that the dealership probably installed right before I bought it. The voltage tested at 12.1 on the multimeter. The new battery tested at 12.9. I stuck the new one in, reconnected everything and started the vehicle. No more ESS warning light.
So 2 questions: Is 12.1 actually considered low voltage, enough to cause the ESS system to stop working? And what would cause the battery to fail, if indeed that's what it is, after just one year? (And the original after 2 years?)

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[Deke]

Was your 12.1v test result with the battery under a load? I've had many batteries show good voltage with a multimeter but fall below 12v as soon as any load was put on them.

 

[Walker Texas Wrangler]

I'm not surprised. My Jeep was purchased in March brand new and I'm having issues with the Start/Stop not engaging. I'm going to take it in, but if these aux batteries only last a year, it's a major design flaw. Especially since they are buried in the compartment. There really needs to be a recall on this that would be a more permanent fix. Huge fail.

 

[redracer]

It's truly just a bad design to have two dissimilar batteries in parallel. This arrangement just dooms both batteries to early failure every time.

The fix, is to pull the aux battery and to never replace it. Tape up the cable terminals and pull the control wire connector from the stop start relay that's on the firewall just behind the aux battery box. that's it.

And, auto stop start still works...

 

[MtCamper]

12.1 is about 50% of a fully charged battery. Either it's not charging or it's just bad. From my experience you're very fortunate you were able to still start the jeep. Your 18 must have had the software update to allow that with a discharged aux battery. That's good. Read the previous post about the N3 fuse. I'm sure there is another way to test it, but I found it best to remove all the wires and just pull the damn thing out. Then run it with a continuity tester. I got stranded 20 miles back when I had a short and N7 blew. The short was my fault. Now I carry a spare high amp fuse bar. I'd also recommend you pop off the cover to the secret transmission bypass just to make sure you know where it is hand how to get to it.

 

[Heimkehr]

Is 12.1 actually considered low voltage, enough to cause the ESS system to stop working?

And what would cause the battery to fail, if indeed that's what it is, after just one year? (And the original after 2 years?)

My personal standard for a battery's lowest permissible resting voltage is 12.3 volts. A properly authenticated 12.1 volt measurement would likely prompt me to replace the battery in question. This is doubly true if there's context (i.e., user experience) to justify the expense.

I also expect a 12V battery to provide a 5 year service life, irrespective of application. But for one recent exception, which I correctly anticipated would occur, every 12V battery I've ever owned/used has lasted +/-6 years. Seasonal-use batteries are connected to a battery tender for the sum of time that they're removed from active use.

The jury is still out regarding how long the little motorcycle battery under the hood of my '21 JLU will last. Based on recurring threads such as this one, I've already earmarked the expense of this upgrade as something that will eventually have to occur.

The EPA can take a long walk off of a short pier for compelling the OEMs to chase patchwork solutions to fuel efficiency requirements such as the Engine Start/Stop function.

 

[mwilk012]

Don’t replace with a. Mopar battery. They’re very bad.

 

[191185]

It's truly just a bad design to have two dissimilar batteries in parallel. This arrangement just dooms both batteries to early failure every time.

The fix, is to pull the aux battery and to never replace it. Tape up the cable terminals and pull the control wire connector from the stop start relay that's on the firewall just behind the aux battery box. that's it.

And, auto stop start still works...

When you do this .. Which I think I'm going to, do you beef up the main battery with a higher capacity when you replace it? Or are you running the dual battery setup ?

 

[WAOLIFE]

I have a 2018 JLU that I bought one year ago, October 2020. The ESS warning light on the dash has been on for 6 months, and I finally got around to ordering a replacement aux battery and the clips to reinstall the fender flare, and yesterday I dug in to do the job. Pulled the old battery out (a Mopar), and immediately noticed a sticker on the side that said "Shipped Sept 2020." So this is not the original battery that was due to be replaced at the 3-year mark, but instead a one-year old battery that the dealership probably installed right before I bought it. The voltage tested at 12.1 on the multimeter. The new battery tested at 12.9. I stuck the new one in, reconnected everything and started the vehicle. No more ESS warning light.
So 2 questions: Is 12.1 actually considered low voltage, enough to cause the ESS system to stop working? And what would cause the battery to fail, if indeed that's what it is, after just one year? (And the original after 2 years?)

I lost both of mine the same day, a hair after 2 years. They aren't the best battery for OEM, and I run a Dometic and Jackery on occasion so I'm sure that helped kill them off faster. Good thing is they are under warranty and they towed me in and replaced them both with ZERO out of pocket.

 

[humpndunk]

So like I said earlier I put the new battery in, started it up and the ESS warning light has gone away. I did get the message "Stop/Start Unavailable, battery is charging", but I drove around town for 10 minutes and all of a sudden at a stop light the engine died. Wait, it didn't die, that's the ESS system working properly now. I haven't seen it work in 6 months so it surprised me.
Also, since I don't know why the last battery didn't last even a year, I decided to check that N3 fuse that controls charging of the aux battery. I've never seen a fuse like this so look at the picture and tell me if this is the proper way to check the fuses on that high amp fuse bar.

 

[Rhinebeck01]

So like I said earlier I put the new battery in, started it up and the ESS warning light has gone away. I did get the message "Stop/Start Unavailable, battery is charging", but I drove around town for 10 minutes and all of a sudden at a stop light the engine died. Wait, it didn't die, that's the ESS system working properly now. I haven't seen it work in 6 months so it surprised me.
Also, since I don't know why the last battery didn't last even a year, I decided to check that N3 fuse that controls charging of the aux battery. I've never seen a fuse like this so look at the picture and tell me if this is the proper way to check the fuses on that high amp fuse bar.

@humpndunk

Read here:
https://www.jlwranglerforums.com/fo...-cable-caution-and-ess-n3-fuse-warning.66247/

 

[humpndunk]

OK it looks like I'm testing fuse N4 and not N3 in my pic. Thanks for the correction. I did test all of them though and they all looked good.
So what's the best way to test these without removing the bus bar? Put my probes where?

 

[Ogre_FL]

FWIW we just had our 2nd aux battery replaced under warranty (3 batteries now since new).

Just about 1 year ago had the original replaced after a few months of seeing "Stop/Start Unavailable, battery is charging" all the time and the ESS not working.
About 2 months or so ago I noticed the ESS had stopped working again and was seeing the "Stop/Start Unavailable, battery is charging" all the time.
Finally got around to bringing it in last week.

I was actually hoping that it was the main battery this time, but it was the aux again.

VERY disappointing (and worrisome) that the 2nd battery didn't even seem to make it a year.
Never have had any warning lights or any starting issues though.(knock on wood)

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