ESS Battery Dead?

[jebklb]

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.

I called both dealerships within 30 minutes of my home and neither had an appointment for the next week or so. They would not even accommodate a quick drop in. The one closest, a known poor dealership, said they do not have any batteries in stock and I should call back in a few weeks. Go figure!

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[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?

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.

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.

Fudster,

I disconnected ESS as described - the Jeep cranked in the first attempt to start, which is not as described below. Any idea if I’ve done something incorrectly or if there are times it will crank the first time?

Thanks!

Joe

 

[txj2go]

I disconnected ESS as described - the Jeep cranked in the first attempt to start, which is not as described below. Any idea if I’ve done something incorrectly or if there are times it will crank the first time?

I don't recall on mine. It may be that if you have not disconnected the main battery it just operates as normal. I know when I changed batteries it took 2 pushes before it started.

 

[Maverick909]

I called both dealerships within 30 minutes of my home and neither had an appointment for the next week or so. They would not even accommodate a quick drop in. The one closest, a known poor dealership, said they do not have any batteries in stock and I should call back in a few weeks. Go figure!

so i am not sure with the 2.0 battery location I would assume its the same as the 3.6L under the fuse box on the passenger side. the easy way to remove is through the fender. especially if you have after market fender liners

 

[Fudster]

Fudster,

I disconnected ESS as described - the Jeep cranked in the first attempt to start, which is not as described below. Any idea if I’ve done something incorrectly or if there are times it will crank the first time?

Thanks!

Joe

Hi Joe:

Clarify for me. Did you merely disconnect from the main battery's negative terminal the cable whose distal end is NOT the body ground (i.e. the disconnected cable's distal end being the negative terminal of the ESS battery).....


and stop.....(which would be ok if you did?)


or did you proceed to also pull Fuse 42 and/or jumper high amp fuses N1 and N2 in the PDC (which would also be okay if you did that too?)

Does an ESS off light appear in the EVIC (dash)? Did it appear in the dash prior to your mods?

When I know more about the precise extent of your mods, hopefully I can comment better in response.

 

[jebklb]

Hi Joe:

Clarify for me. Did you merely disconnect from the main battery's negative terminal the cable whose distal end is NOT the body ground (i.e. the disconnected cable's distal end being the negative terminal of the ESS battery).....


and stop.....(which would be ok if you did?)


or did you proceed to also pull Fuse 42 and/or jumper high amp fuses N1 and N2 in the PDC (which would also be okay if you did that too?)

Does an ESS off light appear in the EVIC (dash)?

When I know more about the precise extent of your mods, hopefully I can comment better in response.

I only disconnected the main battery's negative terminal is NOT on the body ground. (I just double checked). I did not pull Fuse 42. Also, no "ESS off" lights appearing on the dash. I do have a Tazer Mini but I have NOT disabled the ESS function.

 

[Fudster]

+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.

Bill, I second your props to the Genesis dual battery system, although I do not own it, but wish to add some commentary on the product's best use so that people will not incur this expense to solve the wrong problem.

The Genesis system is a wonderful way of providing your JL with not only more power, but more power management. It can do things like isolate its batteries (sold separately) such that overlanding appliances can be run on one of the batteries, saving the other to crank the engine and get home while the alternator kicks in to replenish both batteries thereafter.

But what it is not is a solution, IMHO, is for people solely frustrated with their ESS batteries. For those individuals I suggest--if running ESS events is not desired, than either

* take the ESS battery out of the electrical schematic of the vehicle as described prior in this thread and force all calls for electrical current to the main battery via a pull of Fuse 42 and/or a fused jumper between high amp fuses N1 and N2 in the PDC, and turn ESS off via a button press or aftermarket tech to effect same, (links available on request) or

* Provided you are not running an early model 2018 that fails to have TSB 18-092-19, take the ESS battery out of the electrical schematic of the vehicle as described prior in this thread ...and stop.

Attempt to crank. I expect the first attempt to fail as no ESS battery is found. Try again. This time the dual AGM battery JL should attempt to crank solely off the main battery. If successful, from that point forward the vehicle should crank on the first try provided the main battery has ample current. Doing this will turn on the ESS off light in the EVIC. Some people hate this. If so, follow the prior guidance. I'd think it a feature. You don't want to run ESS on a JL on one battery, and this approach automatically turns ESS off for you, no aftermarket purchase required.

If running ESS events is desired get use to the idea that you might have to trickle charge your JL when parked--much as multicar garage parking provides little opportunity for this. Put your trickle charger's terminals on the main battery. Both batteries will charge.

Another option for those wanting to run ESS events is to buy the Genesis tray and batteries but no more from the kit, making one of those batteries your main, and the other your ESS, removing the factory batteries (or at least the main one, and disconnecting both) in the process.

Interesting enough, the Genesis system will limit you to 6 ESS events per crank. This is because the kit sees identical voltages in the two batteries (because it reads a composite voltage of the two batteries.) After 6 times your dual AGM battery JL is going to think there is a short somewhere and turn off ESS until the next cold crank.

Not a big deal, but for ESS lovers (who meet in a phone booth), not a solution.

 

[Fudster]

I only disconnected the main battery's negative terminal is NOT on the body ground. (I just double checked). I did not pull Fuse 42. Also, no "ESS off" lights appearing on the dash. I do have a Tazer Mini but I have NOT disabled the ESS function.

Got it. Your running a dual AGM battery model year 2021 JL, and you only disconnected the black cable from the main battery whose other end is NOT the body ground on the passenger's side front quarter panel. The cable from the body ground to the negative terminal of the main battery is connected.

You have no fused jumper between high amp fuses N1 and N2 in the PDC--which would be an aftermarket mod, not factory, and Fuse 42 is intact--check to see that Fuse 42 is seated well.

After doing this you cranked immediately and the ESS off light did not appear in the dash.

All I can say is that the first thing I'd look for is that Fuse 42 is seated well. Did you isolate the loose end of the cable you removed such that it comes into contact with nothing, especially not metal.

If Fuse 42 is loose a relay that separates the batteries when energized can't work. The relay is energized for an instant during a normal crank to test the ESS battery, and during ESS events. If the relay isn't getting power then any calls for current to any battery go to all available batteries silently, without any notice from the vehicle's computer, and since you disconnected the ESS battery, all batteries are only your main battery.

What engine (e.g. 3.6L, 2.0 Turbo) is your 2021?

Beyond that, I humbly remain stumped. It's not my first guess but maybe the married Tazer plays a role here.

P.S. I hate to leave you stranded, either without explanation or on these weekend's trip. Can I interest you in buying a portable jumper starter for peace of mind?

 

[shadango]

Fudster,

I am in awe of your EXTREMELY clear info on this topic.

IMHO its ridiculous that folks like me with brand new Jeeps have to worry about being stranded due to a poor battery system design...I mean.....ITS A JEEP! It should be ready to go!

Our Jeep has another 11 months on the bumper to bumper, which is SUPPOSED to cover the batteries...but when dealers dont have BATTERIES in stock and have long wait time, exactly what do they expect you to do?!

That said, I have some questions I am hoping you can answer....

I have the 2.0T in my '21.....My late wife bought it two years and a month ago.

When I started hearing about this issue I started watching the voltmeter while driving....it seems to hang around 14.2-14.4 most times. I normally do turn off the ESS manually....but when I forget, at stops the voltage drops (as expected) to 13.9-13.0-ish...occassionally to 12.8 depending on how many accessories I have going)....voltage comes back up when the engine kicks on as expected.

Do you know if any "heads up" is given when the smaller battery has gotten to the point where it is ruining the main battery? Will the voltmeter give any clue in advance?

If the small battery DOES "kill" the main battery and I come out one morning and cannot crank, my plan would be to immediately disconnect that black-cable-to small battery at the main battery post and pull that #42 fuse......I assume then that I should be able to jump the main battery to get her running as on a "normal" vehicle without the dual battery stuff? Or will it really KILL the main battery?

I was considering doing the above (disconnect the small battery black cable from the main black terminal and yank #42) BEFORE I have the issue......you said the "ESS OFF" light comes on (like it always does when I manually hit the switch)......do you still have to hit the button? Or just leave that alone?

Is there any downside to just letting the currently-ok small battery "waste away" being un-connected if I do the "disconnect the small battery black cable from the main black terminal and yank #42" process now? Aside from the dealer maybe squawking if they find out) and running it that way every day?

I usually get 4-5 years out of my regular car AGM batteries so worrying about this NOW at 2 years just stinks!

Thanks again!

 

[jebklb]

Got it. Your running a dual AGM battery model year 2021 JL, and you only disconnected the black cable from the main battery whose other end is NOT the body ground on the passenger's side front quarter panel. The cable from the body ground to the negative terminal of the main battery is connected.

You have no fused jumper between high amp fuses N1 and N2 in the PDC--which would be an aftermarket mod, not factory, and Fuse 42 is intact--check to see that Fuse 42 is seated well.

After doing this you cranked immediately and the ESS off light did not appear in the dash.

All I can say is that the first thing I'd look for is that Fuse 42 is seated well. Did you isolate the loose end of the cable you removed such that it comes into contact with nothing, especially not metal.

If Fuse 42 is loose a relay that separates the batteries when energized can't work. The relay is energized for an instant during a normal crank to test the ESS battery, and during ESS events. If the relay isn't getting power then any calls for current to any battery go to all available batteries silently, without any notice from the vehicle's computer, and since you disconnected the ESS battery, all batteries are only your main battery.

What engine (e.g. 3.6L, 2.0 Turbo) is your 2021?

Beyond that, I humbly remain stumped. It's not my first guess but maybe the married Tazer plays a role here.

P.S. I hate to leave you stranded, either without explanation or on these weekend's trip. Can I interest you in buying a portable jumper starter for peace of mind?

Soooo.....you should no longer be stumped and I am throughly embarrassed to say that after double checking I went back to triple check and I had disconnected the wrong cable (old age sucks, but it is better than the alternative). Now, after following your instructions CORRECTLY I am to the point where the JL did not start the first time after disconnecting the cable and the ESS light is on.

I plan to run as is over the weekend and then look at some of the options mentioned here (Genesis dual battery system and portable jumper).

I am very thankful you took the time to walk me through this!

 

[Fudster]

Soooo.....you should no longer be stumped and I am throughly embarrassed to say that after double checking I went back to triple check and I had disconnected the wrong cable (old age sucks, but it is better than the alternative). Now, after following your instructions CORRECTLY I am to the point where the JL did not start the first time after disconnecting the cable and the ESS light is on.

I plan to run as is over the weekend and then look at some of the options mentioned here (Genesis dual battery system and portable jumper).

I am very thankful you took the time to walk me through this!

My pleasure.

Joe..so that we're on the same page, (and so I can mentally close out this thread in my head) the vehicle does not indeed not only start, but on the first crank now, correct sir?

 

[jebklb]

My pleasure.

Joe..so that we're on the same page, (and so I can mentally close out this thread in my head) the vehicle does not indeed not only start, but on the first crank now, correct sir?

Correct, close out the thread in your head.

 

[Fudster]

Fudster,


IMHO its ridiculous that folks like me with brand new Jeeps have to worry about being stranded due to a poor battery system design...I mean.....ITS A JEEP! It should be ready to go!

I completely agree, and yet, interesting enough, my finger is more pointed at the EPA than Stellantis here, and so you should know my biases I am an environmentally leaning person who believes in the EPAs mission.

That said, and to keep me off my soapbox, the CAFE rules for automobile manufacturers to be able to advertise their best mileage ratings incentivizes an ESS system in the JL that is more designed to pass a one time EPA test than our daily driving. The rules need review.

Stellantis could of course design a better ESS system, but we'd end up paying for it in part in purchase price. They didn't want to go with a one battery ESS system like so many other manufacturers because, I suspect, owners tend to add power hungry appliances that could rob a sole cranking battery.

Our Jeep has another 11 months on the bumper to bumper, which is SUPPOSED to cover the batteries...but when dealers dont have BATTERIES in stock and have long wait time, exactly what do they expect you to do?!

Again, your sentiments resonate well. I was contemplating stocking a backup ESS battery as a result of hearing things like what you've said above. A couple of thoughts. There are some excellent posts (links available on request) that detail the 3rd party batteries, both main and ESS ,that you can purchase--not that you should have to.

I'd suggest that you chat with @JeepCares on this one (now) so as to guarantee that potential battery defects that occur in the warranty period are handled gratis after that window of time if MOPAR parts to rectify the issue only became available after that window.

Let me get more philosophical about your question regarding what Jeep expects us to do.

Love my Wrangler though I do, aspects of the vehicle have been allowed to fall short in terms of included and/or add on MOPAR equipment because of historical limited competition in the vehicle space and the realization that such shortfalls are addressed by the aftermarket in better and cheaper product. For this reason alone I welcome the competition that Ford's rollout of the redesigned (not so) new Bronco brings.

Another aspect of the Jeep community that has been expected of us lies in the Marine's motto of "improvise, adapt, and overcome." We shouldn't have to but we do. And if I were managing a team faced with this famous American problem, I might be inclined to ask initially ask, "ok, who among you engineers owns a Jeep." Those would be my guys and gals who know how to put a square peg in a round hole if necessary, to solve a problem.

That said, I have some questions I am hoping you can answer....

I have the 2.0T in my '21.....My late wife bought it two years and a month ago.

When I started hearing about this issue I started watching the voltmeter while driving....it seems to hang around 14.2-14.4 most times. I normally do turn off the ESS manually....but when I forget, at stops the voltage drops (as expected) to 13.9-13.0-ish...occassionally to 12.8 depending on how many accessories I have going)....voltage comes back up when the engine kicks on as expected.

The EVIC display of voltage, I believe, serves two useful functions. The first, during non-ESS events tells me how hard the smart alternator is working to replenish power that's been drawn from the batteries. As a smart alternator, it will demand less of the engine (read gasoline) in times when the batteries are charged and/or are charging well (i.e. accepting charge well.) While I own a 3.6L, that 14+ voltage reading your referring to would lead me to have each battery independently load tested., as it seems to be a high voltage reading.

As you are probably aware, load testing gauges how well a battery does that very thing it needs to do: accept and deliver charge.

The second use of the EVIC allows me to watch the ESS' batteries voltage during ESS events. At such times it is only this battery's voltage that the EVIC displays.

To rephrase, a high EVIC voltage reading during non-ESS events more symbolizing to me a need to load test batteries, not some point of pride in how well my alternator is working.

Do you know if any "heads up" is given when the smaller battery has gotten to the point where it is ruining the main battery? Will the voltmeter give any clue in advance?

Sadly, no advance notice warning is expressly communicated to the operator by the vehicle of impending doom. We look for signs like a slower crank, electronics acting squirrelly, but no.

That said there are some things you can do. At the most orthodox end of the range lies a system the Godfather of JL battery knowledge Jerry (@Jebiruph) set up to monitor each battery's voltage https://www.jlwranglerforums.com/forum/threads/ess-dual-battery-management.60034/

This link comes from a posting of most of his important battery findings found here:

https://www.jlwranglerforums.com/forum/threads/3-6l-ess-dual-battery-consolidated-information.25377/

And included at the aforementioned link is one where he talks about how to load test the batteries.

https://www.jlwranglerforums.com/forum/threads/3-6l-ess-battery-basic-load-testing.22031/

This stuff can be a lot of work or not so much depending on how much someone wants to monitor their batteries.

In a simpler version I have one of these on my main battery's negative terminal, upon which the negative from the ESS battery is connected.

https://www.amazon.com/gp/product/B07JZ9NDH2/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

When this knife switch is in the open state, putting a battery tester on the main battery will give you a reading of only the main battery. If the switch is closed the reading is a composite of both batteries which often gleans limited information.

Again with the knife switch open, moving the negative terminal of tester to the cable attached to this knife switch, whose origins are the negative terminal of the ESS battery, will give you a reading of the ESS battery.

That's right....even though your positive tester lead is still on the main battery's positive terminal,, it's the ESS battery that is being tested.

If the small battery DOES "kill" the main battery and I come out one morning and cannot crank, my plan would be to immediately disconnect that black-cable-to small battery at the main battery post and pull that #42 fuse.

Me too. And yet I wouldn't be surprised if it doesn't help. Here's why. Your plan diverts all calls for electrical current to only the main battery. Unfortunately if the ESS battery has, due to defect, cannibalzed the main battery to limited voltage, you may not crank.

I assume then that I should be able to jump the main battery to get her running as on a "normal" vehicle without the dual battery stuff? Or will it really KILL the main battery?

I'd be inclined to say that an otherwise healthy main battery that has been depleted of power by a defective ESS battery--at least for the first few times this happens, will likely be able to accept the charge of your jumper and still have useful life going forward.

FWIW your plan sounds very similar to something I'd do.

I was considering doing the above (disconnect the small battery black cable from the main black terminal and yank #42) BEFORE I have the issue......you said the "ESS OFF" light comes on (like it always does when I manually hit the switch)......do you still have to hit the button? Or just leave that alone?

If the desire to run ESS events really isn't your thing, IMHO the ESS battery is more a hinderance and should be taken out of the vehicle's electric schematic than kept. (Conflict of interest statement: I run both batteries and trickle charge while parked. See above about my environmental guilt @ gasoline.)

That said, let's address the ESS off light. This is best done by running through exactly what happens at cold crank on a dual AGM battery JL.

When you press that brake and start button one of the first things your dual AGM battery JL is going to (try to) do is isolate the ESS battery to test its voltage. It will do, or attempt to do this by energizing a relay that separates the batteries--otherwise the batteris are always connected in parallel but for this instant, and during ESS events.

If Fuse 42 is pulled this relay cannot get electrical current and fails (to separate the batteries) without so much a of whimper. Your JL then "tests its ESS battery" or so it thinks--which because the relay is dead, turns out to be all the batteries that are connected--which in your case is only the main battery.

You have tricked your JL into thinking that your main battery is both your main and ESS battery.

Provided that your main battery has adequate current, the ESS off (in the dash---I'm not talking about the one on the ESS off switch below near the radio) light shouldn't illuminate in the dash and the JL should crank. I encourage you to turn ESS off with a button push or aftermarket tech. Running ESS events with one battery depletes that battery of cranking power at the end of the ESS event. Sure, plenty of vehicles run ESS with one battery and it isn't usually the end of the world if you forget, but the "perfect storm" of an aged main battery running an ESS event at a traffic light, while your aftermarket sound system and lights that could "land a plane" are drawing major current could leave your ability to re-crank the engine and get the alternator going compromised.

Let's talk about another scenario. This one involves merely disconnecting the ESS battery's negative cable from the main battery's negative terminal and stopping. No Fuse 42 pull, no N1 to N2 fused jumper. (The latter was the original technique to insure the batteries are always in parallel.)

Now, since you are NOT running an early model 2018, your initial attempt to cold crank will fail (only the first time) because no ESS battery was found when that relay was energized. But the second attempt to cold crank, and those thereafter will be against only the main battery. If it is successful, in this scenario the ESS off light in the dash (i.e. EVIC, not the light on the button) will illuminate.

Your JL is saying, "I'm not allowing ESS events because I detected no current on the ESS battery."

Forever more your cold cranks should work on the first try going only against the main battery, and illuminating that ESS off light in the dash. No aftermarket tech to turn off ESS is needed; no push of the button. But some people hate this ESS off light in the dash, in which case I recommend the additional Fuse 42 pull to trick the vehicle, with operator involved turning off of ESS (button push, aftermarket tech, etc.)

Only the cold crank after an energized ESS battery is reconnectted, if ever, will that ESS off light be turned off.

Is there any downside to just letting the currently-ok small battery "waste away" being un-connected if I do the "disconnect the small battery black cable from the main black terminal and yank #42" process now? Aside from the dealer maybe squawking if they find out) and running it that way every day?

IMHO there is not. Even if that battery's casing were to be compromised over the years, it sits closest to the ground with no vehicle components under it to corrode from acid spill.

Some forum members like to keep that ESS battery independently charged. Again, this is easiest done by putting your charger's negative side on the dangling cable you disconnected and the positive side on the main (that's right, I said main) battery's positive terminal.

I usually get 4-5 years out of my regular car AGM batteries so worrying about this NOW at 2 years just stinks!

Thanks again!

I change my JLs batteries every 3 years. I wish their MTBF (mean time between failure) metrics were better.

 

[Fudster]

All:

Until "Mr. Rhinebeck" uses his words, not mocking laughing icons at content which is not, nor intended to be funny, please take his childish gestures as that of someone who has no factual rebuttal and ignore them.

Thanks.

Put your laughing icon right there Rhinebeck \/ It won't change facts.

 

[txj2go]

To the OP- you can see from some of these posts that the dual battery system is a very complex issue. There have been some very long threads about this in the past.

IMHO its ridiculous that folks like me with brand new Jeeps have to worry about being stranded due to a poor battery system design...I mean.....ITS A JEEP! It should be ready to go!

Our Jeep has another 11 months on the bumper to bumper, which is SUPPOSED to cover the batteries...but when dealers dont have BATTERIES in stock and have long wait time, exactly what do they expect you to do?!

It depends on your situation but I will suggest that the battery they would give you is going to be of questionable quality. If reliability is important to you then my previous recommendation was to bypass the dealer and buy the very best aftermarket battery you can find. If you want a potentially even more reliable system then get the (expensive) dual battery setup and put 2 quality batteries in it. To cover everybody- some people with 2018 models will need to do a little more work to ditch the little battery, I didn't have to do that with my 2018. My dash display does have the ESS error light turned on so I have to learn to ignore it.

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