ESS Battery Dead?

[jebklb]

My Jeep wouldn’t start! ?. It’s a 2021 with 10K miles. I figured it was one of the batteries and tried to jump start it. No joy there. I put a battery charger on it and 10 hours later it started. I had the main battery tested and it is fine, but I didn’t try to get to the auxiliary battery. One of my local dealerships says the auxiliary battery is back ordered and I should call back in a few weeks.

Long story to say I’m going out wheeling this weekend - should I be overly concerned about getting stranded 4 hours from home?

Thanks!

Sponsored

 

[Fudster]

Joe:

When you had the main battery tested was it with a volt meter or--the gold standard-a load tester?

And regardless, when you had this test done, was the ESS battery disconnected from the main battery?

If not, you got a composite reading of both batteries together, from which you can draw little conclusion about either battery individually.

I suggest that you locate the two black factory cables on the main battery's negative post. One leads to the body ground on the passenger's side front panel. Leave that cable connected.

The other cable, whose distal end is connected to the ESS battery's negative terminal, should be removed from the main battery and its end wrapped up and tucked away.

Then, load test the main battery.

If your main battery is adequately charged the 2021 may fail on its initial crank, because no ESS battery will be detected with this cable pull, but subsequent crank attempts should go off the main battery.

If successful, all subsequent cranks should happen against the main battery only, on the first try, and the vehicle will turn off ESS, as indicated in the dash until, if ever, an energized ESS battery is reintroduced into the vehicle and that cable is reconnected.

This ESS off light is just as well IMHO, as running ESS events on one battery isn't advised.

If you hate this ESS off light you can pull Fuse 42 in the Power Distribution Center. Much as been written here on that if you search.

Pulling this fuse will prevent the batteries from ever being isolated. The vehicle's calls to only the ESS battery will be to all batteries, which in your case will be only the main battery. Effectively you will have tricked the vehicle's computer into thinking it tested the ESS battery, as pulling Fuse 42, which prevents a relay from energizing that separates the batteries, is a silent change unknown to the vehicle.

Make sure to turn ESS off at the button if you pull Fuse 42.

If your load test of the main battery passes and you effect the guidance here you should be fine, at least from an electrical standpoint provided what caused your issue was a failing ESS battery that canabilized the main one, as opposed to (perhaps in combination) some electrical short that drained your batteries independent of a bad ESS battery.

P.S. When you say you put a battery charger on it, was that the main battery's terminals? And if so was the ESS battery connected to it. If so, your charger applied current to both batteries as they are connected in parallel from the factory at all times but an instant at cold crank (baring the Fuse 42 pull) and during ESS events.

 

[txj2go]

If you are dedicated to making the ESS function then you will probably need a new small battery. Otherwise my recommendation is to disconnect the small battery and not worry about it any further. I've been running with my small battery disconnected for over 2 years.

 

[Fudster]

If you are dedicated to making the ESS function then you will probably need a new small battery. Otherwise my recommendation is to disconnect the small battery and not worry about it any further. I've been running with my small battery disconnected for over 2 years.

Early 2018 owners:

Merely disconnecting the ESS battery without having TSB 18-092-19 applied to your vehicle by a dealer will leave you with a JL that won't crank.

For newer owners with dual batteries, the first crank should fail but subsequent one should be ok consistent with my above response.

 

[Rhinebeck01]

@txj2go
Contrary to what you were just told... Do know that ...

If you do an aux battery bypass on a 2018 it will start even if the vehicle has not had TSB 18-092-19 applied to the vehicle by a dealer.

Also, not all 2018's benefit from the TSB. Some later production model year 2018's behave just like 2019 and newer JL's

 

[jebklb]

Joe:

When you had the main battery tested was it with a volt meter or--the gold standard-a load tester?

And regardless, when you had this test done, was the ESS battery disconnected from the main battery?

P.S. When you say you put a battery charger on it, was that the main battery's terminals? And if so was the ESS battery connected to it. If so, your charger applied current to both batteries as they are connected in parallel from the factory at all times but an instant at cold crank (baring the Fuse 42 pull) and during ESS events.

Thank you for taking the time to write such a great response, it gives me a way forward!

Yes, a load tester was used. Unfortunately, I did not disconnect the ESS battery so the test is inconclusive. Also, yes, when I put the charger on the battery, it was on the main terminals.

I plan to go through the above and hopefully figure this out today.

 

[jebklb]

If you are dedicated to making the ESS function then you will probably need a new small battery. Otherwise my recommendation is to disconnect the small battery and not worry about it any further. I've been running with my small battery disconnected for over 2 years.

I think that is my plan. After doing a little research, mostly on this site, it appears to save very little gas.

 

[Steph1]

Had the battery problem twice myself . The second time, instead of changing the batteries again, I installed an underhood charger. Now when I see that the stop/start hesitates to operate on a commute to work, I plug it in overnight and all is like new again. Have had it for around 2 years now and never had a problem since.

If interested do a search on this forum and you’ll find the info.

 

[txj2go]

@txj2go
Contrary to what you were just told... Do know that ...

Yes I know all of that, I've read all of those very long threads in the past. I should have added that some 2018s require more than just disconnecting the small battery (mine didn't). The OP stated he had a 2021 so I went straight to that.

 

[Maverick909]

Ive yet to change either batteries in my 18 JLU. 4 years and counting. i do tend to put it on the tender once a month for 24 hours but i also do not daily my jeep. on the pricier side you can get the genesis Dual battery system. its extreamly well made. I am waiting for one of the batteries to fail before i order the dual big batteries currently

 

[txj2go]

Ive yet to change either batteries in my 18 JLU. 4 years and counting. i do tend to put it on the tender once a month for 24 hours but i also do not daily my jeep. on the pricier side you can get the genesis Dual battery system. its extreamly well made. I am waiting for one of the batteries to fail before i order the dual big batteries currently

There are a lot of factors that affect battery life, luck being one of them. Not driving every day and keeping the system charged are both things that help a lot.

The quality of the original batteries seems to be questionable. A lot of people have reported failures around 2 years. I replaced the battery when my 2018 was 3 years old because I wanted a known good battery in it, and discovered that the battery I removed from the 3 year old vehicle was only 2 years old, so the previous owner had it replaced at 1 year old. I bought the best battery I could find to replace it with and left the small battery disconnected.

My father owned a garage for over 60 years, my experience was that a flooded lead battery would last no more than 3 years if the battery is in the engine compartment and the vehicle is driven every day in a warm environment. AGM batteries are said to last twice as long meaning we should all be getting at least 5 years if we start with a good quality battery.

 

[devicemanager]

Long story to say I’m going out wheeling this weekend - should I be overly concerned about getting stranded 4 hours from home?

I would be. If it were me I'd call my local Jeep dealer to see if they can load test the battery and get it covered under warranty. If it tested good, and they won't replace it, then I'd go buy a new AGM main battery without turning in your old one as a core since you can typically do that later at some stores. My main Mopar oem battery failed right at the 3 year mark.

 

[Bill_BCNtoNY]

Ive yet to change either batteries in my 18 JLU. 4 years and counting. i do tend to put it on the tender once a month for 24 hours but i also do not daily my jeep. on the pricier side you can get the genesis Dual battery system. its extreamly well made. I am waiting for one of the batteries to fail before i order the dual big batteries currently

+1 on the Genesis dual battery system. It’s pricy “insurance”, but I just installed mine on my new-to-me ‘19 that was on the original batteries and am looking forward to some peace of mind (which is a personal thing, I know) on the battery front.

 

[Maverick909]

+1 on the Genesis dual battery system. It’s pricy “insurance”, but I just installed mine on my new-to-me ‘19 that was on the original batteries and am looking forward to some peace of mind (which is a personal thing, I know) on the battery front.

me too. Did you get the newest setup with the engine " On" wire? heard it allows the batteries to be connecting to work quicker for keeping both fully charged

 

[Bill_BCNtoNY]

me too. Did you get the newest setup with the engine " On" wire? heard it allows the batteries to be connecting to work quicker for keeping both fully charged

yes, I got that but skipped on the g screen control (for now). I expect to keep in auto mode all the time anyway.

It was an intense install for me being inexperienced, but their video was good and I learned a lot about all the stuff on that side of the engine well!

Sponsored