3.6L ESS Dual Battery Consolidated Information

[AndySpill]

There's precious little conceptual or real-world evidence for the @Rahneld, @Gee-pah, @Fudster, Spill theory of one-battery-mod ESS restart failure.

As a practical matter, ESS is rather aggressively preemptively disabled based on CR[an]K battery SOC/SOF data from the IBS.

...and Foster thus will come out to jump start your JL, stuck on the highway in the worst of places because people couldn't crank after a particularly taxing and early terminated ESS event run on one battery (in a dual AGM battery JL) whose appliances, cold conditions and aging battery found that battery lacking ample charge to crank by the time the vehicle early terminated the ESS event.

Tell me Foster, if ESS is so rather aggressively preemptively disabled in dual AGM battery JLs then why did Stellantis introduce a second battery to run ESS events?...because they had nothing better to do than unnecessarily raise the vehicle's cost with a battery that also raises the maintenance cost of the vehicle in its tendency to cannabolize the main battery?

Bottom line, once the ESS event kicks in, depite all the tests you reference, the factors that dictate its early termination in a one battery situation (in a dual AGM battery JL), may do so after that one battery lacks sufficient cranking power...or it may not. I think people are foolish to chance it.

99.999% of people who disable the ESS battery also dislike ESS events. I strongly encourage people who dislike ESS to yank this battery, and people who want ESS functionality to run with battery that provides dedicated power in these events (exception: the Genesis 3 is fine in its running these events with its two combined larger batteries in parallel.)

Debating the efficacy of running ESS on one battery in these JLs is the ultimate pinhead discourse where the 6 cycle limitation you emphasize misses the real point: that you shouldn't run ESS in the first place in these scenarios.

Let's do a cost benefit analysis here champ, weighing the gas savings of running ESS with one battery over the safety of an engine that is working when you're about the make that left hand turn over the highway at 2am and 15 degrees F outside.

Oh, and by the way, that testing you refer to: prior to cold crank, under the factory setup it is the ESS battery that is tested: which when you yank that battery's connection and pull Fuse 42 now becomes, unknown to the vehicle, the main battery being tested, leading the vehicle to often conclude, falsely, that its running a top of the line ESS charged battery because what really got tested, unknown the vehicle, was a beefier main battery over the disconnected ESS one.

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[THAW]

Oh, and by the way, that testing you refer to: prior to cold crank, under the factory setup it is the ESS battery that is tested: ...

Incorrect; you clearly lack a full understanding of ESS and IBS functionality.

ESS becomes "not ready" any time the IBS detects CR[an]K (aka main) battery SOC is 65% or lower. The IBS also estimates a SOF parameter used to disable ESS when the CR[an]K battery might lack sufficient power to start the vehicle.

 

[AndySpill]

Incorrect; you clearly lack a full understanding of ESS and IBS functionality.

ESS becomes "not ready" any time the IBS detects CR[an]K (aka main) battery SOC is 65% or lower. The IBS also estimates a SOF parameter used to disable ESS when the CR[an]K battery might lack sufficient power to start the vehicle.

Yesh..at cold crank the ESS battery is polled independent of the main, provided it's connected and the PCR can energize (read Fuse 42 is intact.) You entirely skipped over the fact that your precious diagnostics are at this time polling a battery they weren't intended to test (the main, instead of the factory ESS) as per the factory configuration.

I never claimed this the only test. You wrongly assume that this is what I believe and it's lead you to this wrong conclusion as to my level of understanding.

If that ESS battery lacks sufficient power early 2018 dual AGM JLs won't even crank unless TSB 18-902-19 has been flashed. New model dual AGM battery JLs won't crank on the first attempt, turning ESS off and cranking solely against the main battery on subsequent attempts.

You want to put your faith in the additional diagnostics, themselves calibrated to a dual battery ESS running setup, and run ESS events on one battery, go right ahead. But it's irresponsible to suggest others act in kind--not that anyone does, as we can probably fit into a phone booth the number of people who deliberately run ESS events with one battery on dual AGM battery JLs.

While you are busy splitting hairs with your 6 ESS event per cold crank limitation: something I've never even achieved in 6 years of ownership, I'm in the real world weighing the benefit of saving pennies in gasoline over the safety of not getting stuck, post ESS event, unable to crank, and what the might cost someone.

And lest anyone think I come here with bias: I run dual factory batteries and ESS events and trickle charge. I don't care if you act in kind or turn off ESS or pull the ESS battery and turn off ESS.

I care that you don't tempt fate running ESS events with one battery. It is too liberal a position to take for the myriad of owners, some of whom might be running heavy current drawing aftermarket appliances that drain on old battery in an ESS event so fast that by the time the event early terminates, insufficient power exists to get the engine started.

 

[azjl#3]

I see tech writing opportunity in someones future, thank you well done.

 

[THAW]

You entirely skipped over the fact that your precious diagnostics are at this time polling a battery they weren't intended to test (the main, instead of the factory ESS) as per the factory configuration.

I never claimed this the only test. You wrongly assume that this is what I believe and it's lead you to this wrong conclusion as to my level of understanding.

You continue to demonstrate limited understanding of testing function and parameters.

I'm not overlooking AUX (ESS) battery voltage test design; I stated testing and ESS pre-conditions are far more robust for the CR[an]K battery due to the IBS - which extensively monitors exclusively the CR[an]K battery, regardless of AUX (ESS) battery configuration.

The fact is: ESS stops are, by design, disabled long before the CR[an]K battery is anywhere near borderline for a restart.

Not to mention, your aftermarket accessory theory doesn't hold much water because the IBS tracks real-time and cumulative in/out current as part of the SOC parameter used in ESS disable logic.

 

[Mguy]

For the two posters who want to understand the battery "self-testing" alternator equipped JLs do for ESS operation, but apparently have trouble finding the PDF in the sticky thread above ("Stellantis Authored . . . "), here's the part on page two that needs to be learned:

The PCM can determine the SOC of each battery during a cranking event when the batteries are isolated for a brief period during initial starter engagement. During this period, the battery voltage provided to the PCM is coming from only the auxiliary battery, and the battery voltage reported from the IBS will only be reporting the main battery voltage. This helps the PCM to make a determination on allowing ESS operation.

However, the two poster discussion in this thread (and elsewhere) has virtually no relevance for owners with alternator JLs. Owners who don't use ESS and have done the aux battery/F42 disconnect don't need "self-testing." Their Jeeps will behave like typical vehicles with typical batteries. All other owners shouldn't trust ESS "self-testing" (as experiences told on this forum demonstrate) but should routinely monitor, and provide regular care, for both batteries' state of charge and health.

 

[THAW]

("Stellantis Authored . . . "), here's the part on page two that needs to be learned:

The PCM can determine the SOC of each battery during a cranking event when the batteries are isolated for a brief period during initial starter engagement. During this period, the battery voltage provided to the PCM is coming from only the auxiliary battery, and the battery voltage reported from the IBS will only be reporting the main battery voltage. This helps the PCM to make a determination on allowing ESS operation.

FYI: that repair document PDF is from cardiagn.com - it likely has little to nothing to do with Stellantis. In any case, it's not particularly accurate.

Don't let sloppy transposition of the terms SOC and voltage in that excerpt fool you, it is the IBS that performs SOC estimation. It does so exclusively for the CR[an]K (aka main) battery.
(Visit the IBS link in the opening post to learn about how it works.)

So, the PCM receives a long-term CR[an]K battery SOC estimate from the IBS (via the BCM). Separately, to assess the AUX (ESS) battery, the PCM uses brief system voltage tests during PCR open state (requests).

Bottom Line: ESS is disabled based on a voltage threshold for the AUX (ESS) battery and/or independent, more comprehensive SOC/SOF thresholds for the CR[an]K battery.

(The CR[an]K battery SOC-based ESS threshold is a verifiable fact. I have personally witnessed the dash ESS display switch from "not ready" to "ready" simultaneously with JScan showing IBS SOC increase from 65% to 66%.)

@Mguy, if you're interested in how the JL battery-related systems actually work, JScan is your friend.

 

[Bob Burd]

Get a room already.

 

[Terrymo]

Foster's explanation of both the lack of cable and fuse pull not disabling ESS, and the 6 ESS event limitation per cold crank, while true, is yet another example, IMHO, if him getting so bogged down in minutiae, factual though it may be on dual AGM battery JLs, that he loses sight of the "forest for the trees."

@Ismor, people: whether you want to run ESS events or not: it's all good to me. But if you choose to want to have such (ESS) engine start stop capabilities then please either keep an Aux battery connected, or acquire a Genesis Offroad Gen 3 kit: which by the way will still limit you to 6 ESS cycles per cold crank (and be enormous overkill just for ESS functionality,) or a Genesis Offroad Stock Battery Replacement (not relocation) kit. (The relocation kit won't buy you more power, just easier battery access once installed.)

I say this for two reasons. The first is numerous reports of people whose entertainment system does not do well with the voltage drops consistent with running ESS events and cranking upon their conclusion off the same one battery. Sure, just about every other manufacturer out there runs ESS stock on one battery, but baring the Bronco, people aren't bound to have the aftermarket appliances running during ESS events that a Wrangler owner might, and I must assume that Ford better addressed such voltage change's effect on their appliances.

The second reason I say this is for safety. Sure, an ESS event will early terminate if battery voltage drops below a threshold, but this threshold was based, at least on the dual AGM battery JL, on you sparing, not using your cranking battery during the ESS event. I'm concerned that a less than pristine main battery, a cold night, one too many appliances running, and a long traffic light finds, along with Murphy's Law, an ESS event early terminating at a point where a main battery running that event just slips below its threshold to effect an engine crank: something I don't want happening in the left hand turn lane of a busy highway.

Regarding arguing, minutia, and semantics…Pot to Kettle Bro

 

[alphawolff]

The PCM can determine the SOC of each battery during a cranking event when the batteries are isolated for a brief period during initial starter engagement. During this period, the battery voltage provided to the PCM is coming from only the auxiliary battery, and the battery voltage reported from the IBS will only be reporting the main battery voltage. This helps the PCM to make a determination on allowing ESS operation.

I want to add onto this here and mention if you attempt to jump your vehicle and it isn't working try jumping the n3 PDC stud instead of the primary battery. In a normal weak battery scenario if the first engine crank fails during this battery isolate test it should attempt to crank with both batteries on the follow up key press. For some reason this logic can get interrupted and you get stuck in this isolated battery test mode. Sometimes the aux battery is so dead the interior effectively power cycles during the crank attempt the process never kicks over to the second dual battery crank phase.

Just something to keep in mind if you find yourself needing a jump

 

[THAW]

I want to add onto this here and mention if you attempt to jump your vehicle and it isn't working try jumping the n3 PDC stud instead of the primary battery. In a normal weak battery scenario if the first engine crank fails during this battery isolate test it should attempt to crank with both batteries on the follow up key press. For some reason this logic can get interrupted and you get stuck in this isolated battery test mode. Sometimes the aux battery is so dead the interior effectively power cycles during the crank attempt the process never kicks over to the second dual battery crank phase.

Just something to keep in mind if you find yourself needing a jump

I think you mean the N1 PDC terminal stud (not N3)?

 

[alphawolff]

I think you mean the N1 PDC terminal stud (not N3)?

No, N3. You can do any of the studs besides N1. I recommend N3 because if the N3 fuse is blown this will allow you to jump and run the vehicle off the jump pack.

 

[THAW]

No, N3. You can do any of the studs besides N1. I recommend N3 because if the N3 fuse is blown this will allow you to jump and run the vehicle off the jump pack.

If the N3 fuse is blown, how does the jump pack power the starter?

And if the AUX (ESS) is so weak it power cycles the system electronics when the PCR is open, how does attaching the jump pack to N3 (or any stud besides N1) help? N3 is disconnected from the AUX (ESS) battery and system electronics when the PCR is open.

 

[alphawolff]

If the N3 fuse is blown, how does the jump pack power the starter?

And if the AUX (ESS) is so weak it power cycles the system electronics when the PCR is open, how does attaching the jump pack to N3 (or any stud besides N1) help? N3 is disconnected from the AUX (ESS) battery and system electronics when the PCR is open.

Dunno brother it just works. It's always great going out to a dead JL being dropped off by a tow truck and just jumping it and seeing the bewildered face of the tow truck driver.

In some rare scenarios you need two jump packs, one on the primary and another on the n3 stud

 

[THAW]

Dunno brother it just works. It's always great going out to a dead JL being dropped off by a tow truck and just jumping it and seeing the bewildered face of the tow truck driver.

In some rare scenarios you need two jump packs, one on the primary and another on the n3 stud

Haha, that's funny about the tow truck drivers.

All I know is, N1 is also known to work.

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