Another battery question{sorry]

[AndySpill]

Voltage displayed will fluctuate between about 12.6 up to 15.0 - depending on battery temperature, battery SoC (state of charge), system load and more.
12.8 indicates the battery/batteries were fully charged and there was no real need to push anything into them.

I agree Bill that the fluctuations in (smart) alternator voltage are typical, but am of the mindset that the only true test of a battery is to independently load test it. To restate, I fear a case where one of the batteries compensates for the other--something possible given that they are most of the time connected in parallel.

OP: to load test the batteries first effect the cable disconnect I described. If you don't the test will be a composite of both batteries and may be unable to isolate a problem if one or more of the batteries indeed has one. Here is an example of a load tester https://www.harborfreight.com/100-amp-612v-battery-load-tester-61747.html

With the cable disconnected put the tester's leads on the main battery and test. Your results will only be for the main battery.

Now move the negative side of the load tester to the temporarily unisulated cable you removed, yes, keeping the positive side of the load tester on the main battery's positive terminal.

That is a load test of only the ESS battery, even though the positive side off the load tester sits on the main battery's positive terminal. That positive terminal indirectly connects to the positive terminal of the ESS battery, and the dangling cable's other end, as mentioned prior, is the negative post of the ESS battery. Only the ESS battery forms a complete circuit with the load tester.

Reinsulate that dangling cable please when done.

the IBS ONLY senses the crank or main battery

Well, with the OPs ESS battery taken out of the electrical schematic of the vehicle thru the cable disconnect I'd certainly agree with that Bill. But its position on the negative terminal of the main battery, normally from the factory also connected to the ESS battery, I would have thought the IBS is normally gathering intel on both batteries..hmm

Further - many of us on the Gladiator side have proven that it's almost as likely for the main battery to fail first. Some have seen battery failure, replaced the main and gotten another year out of the aux battery.

Fair, but I'd be inclined to say not relevant here. Here's why: an ESS/Aux battery that is no longer serving the needs of an owner not desiring to run the ESS system, and disconnected is a situation where neither battery can negatively effect the other, true?

Someone fairly asked the merits of keeping the ESS/Aux battery connected despite no desire to run ESS events. Well, as both batteries from the factory power the engine crank I guess there's that: where an ESS battery helps the main.

To my way of thinking an ESS battery no longer powering ESS events is (sorry, I've used this yucky but clinical analogy before) a mom with genetic propensity for breast cancer (ESS battery failure) no longer breast feeding (running the ESS system) her kids now grown. You yank that ESS battery as sure as an oncological breast surgeon preventitively replaces that breast tissue no longer supplying food with implants.

When a battery fails, there's many ways it can fail -and a dead battery isn't proof that it will kill the second battery. It may, but it may not. The main may fail and kill the aux - it may, or it may not drain the aux.

Fair. Here's a given, not a maybe. A disconnected ESS/Aux battery cannot cannabilize the main battery nor be cannnabilized by it.

It's not "take effect"

You're right. It isn't. That's why there's quotes around it. I felt the mechanism you explained wasn't on point and so I "yata yata yataed" it.

it's overcoming the draw of a dead battery that pulls from the jump pack, or the donor/host vehicle you are jumping from.
It's the same rules that have applied since I first got into automotive electric systems (in which I specialized for about 50 years).
If the battery is "dead", then power from a pack or other vehicle will have to raise the voltage of the dead battery enough to have power to then crank and start the dead vehicle.

Actually, you're right, but only because the OP is yanking the connection to the ESS/Aux battery. Had he not, I would argue that one has to be more patient with the jump starting process than your history describes, before attempting a crank, because you are bringing up to power not just the main but the ESS battery.

Too often people clamp on, jump in and try to start - FAIL.

I agree. See my point about the OPs jump start being like his father's Olsmobile (because of the cable pull,) not faster--and slower if the two factory batteries are connected.

Me - I've enough electrical experience and watch things closely enough - I have no fear of not being able to jump a vehicle so my Jeeps get left alone - ESS and aux battery untouched.

Me too. Between trickle charging and carrying a jumper pack and having already installled, just in case, a knife switch to disconnect the ESS/Aux battery I play it like you.

Not sure where that comes from - the PCR isolates the aux battery only a brief moment for a check.

...and ESS events...

How can it "seek to use only the main battery" ? They are in parallel only when the PCR is closed

...because the PCR is a normally closed relay that is never energized from the factory setup but for an instant at cold crank and ESS events. When normally closed all available batteries are in parallel, and the OP will only have one available battery: the main, hence for the OP, it is only the main battery.

The main battery isn't connected directly to N1. the aux battery is always connected to N1.
only the main battery is connected to the starter directly.

True. Only the main battery is connected to the starter, but it is also connected to N2, which when the PCR isn't energized is connected to N1:

Jerry's diagram:

When the PCR is closed, there may be a small bit of current from the aux battery for cranking, but it's going through a relay and smaller wiring, not going to aid much at all, and if it did, then the drop in voltage due to cranking would kill voltage to N1.

A small bit current..maybe..but enough to crank a JL, in fairness on a relatively new ESS/Aux battery alone:

Would like to see how that is drawn out electrically, a schematic.

As requesed....see above.

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[THAW]

A small bit current..maybe..but enough to crank a JL, in fairness on a relatively new ESS/Aux battery alone:

I think he means the main battery provides the vast majority of starting current because it's connected to the path of least resistance., not that the ESS battery/wiring couldn't supply it.

But the ESS battery starting demo appears to disprove the suggestion N1 voltage would be "killed".

 

[THAW]

My question stems from the physical installation of the IBS evident on our vehicles. If there's intelligence, so to speak, that it uses to segregate batteries for reporting purposes, etc., that's the intel that's being sought.

Another forum member actually diagrammed the ESS current path over the IBS. And, rightly pointed out current could flow between the batteries across the IBS if one is charging the other.

 

[tony58]

so, if I get this correct, if I shut off the ess every time I use the jeep, I would have no issue that the aux battery would drain the main battery, or should I still pull fuse 42 and disconnect the negative cable to the aux battery? You just have to love this ess!!!!

 

[Heimkehr]

so, if I get this correct, if I shut off the ess every time I use the jeep, I would have no issue that the aux battery would drain the main battery, or should I still pull fuse 42 and disconnect the negative cable to the aux battery?

The ESS function on my JLU has been turned off from new, via the use of a defeat harness. 39 months later and the OEM main battery continues to reliably and robustly crank the engine as it's done from new.

I've not disturbed the cables for the ESS battery, nor any related fuses.

 

[AndySpill]

so, if I get this correct, if I shut off the ess every time I use the jeep, I would have no issue that the aux battery would drain the main battery, or should I still pull fuse 42 and disconnect the negative cable to the aux battery? You just have to love this ess!!!!

I completely respect that James @Heimkehr has merely prevented the ESS system from engaging, but not disturbed any aspect of the factory electrical install, specifically not pulling fuses (42) or disconnecting cables to the ESS battery and taking it out of the vehcile's electrical schematic.

That is his choice, and from my reading of his posts, it is without question an informed decision as he knows this subject matter well.

Full disclosure: I'm just like James although I haven't turned off the ESS system. But I also regularly trickle charge my batteries when parked (via solar panel now) given that I already have a roof rack for other reasons, for such a solar panel to reside on.

But all this said, Tony, I repectfully believe your assumption to be wrong. I'll try to explain.

While it is true that your prevention of ESS events from occuring will result in the ESS/Aux battery being less taxed than if you permitted ESS event functionality, the fact remains that this small battery can still over time prove not only troublesome, but in its parallel connection to the main battery, risk cannabolizing it.

And sure, the main battery can do that to the ESS/Aux battery as well, but it's not a fair comparison because you need the main battery. You don't need the ESS/Aux battery particularly if you are not running ESS events.

I am of the opinion, others can disagree, that if an owner chooses to not engage the ESS system that the pros of keeping the ESS battery connected are statistically outweighed by the cons, particularly with the passage of time. Given your choice to not engage the ESS system (my advise would be different if you wanted to run ESS events) I encourage you to disconnect the ESS battery at the main battery's negative terminal and insulate the dangling cable end, and pull Fuse 42 to prevent your dual AGM battery JL from being able to isolate the cables that lead to the ESS/Aux battery.

The pros of keeping the ESS/Aux battery connected are that this battery, when working well, assists the main battery in cranking the engine: something the main battery when not defective, has more than enough power to do on its own. When working well the ESS/Aux battery, as shown in linked prior videos, has enough power to crank the engine all on its own.

Please continue to keep the ESS system from engaging if you take my suggested steps. Allowing it to run could tax the main battery of engine starting power in the perfect storm of a cold night, a long traffic light, a soon to be dead main battery, and lots of current pulling accessories that cause the ESS event to end prematurely due to voltage drop, but not in time for the battery to have the power restart the engine, much that nearly all other vehicles run ESS systems with one battery (albeit sans winches, and lighting systems, and offroad appliances, etc.)

In a perfect world I believe Stellantis would have designed a dual equal size battery system where the batteries periodically switch roles as main an Aux battery. But that would have cost us more, the aftermarket would provide it (Genesis Offroad), and challenged the very fuel economy (a smart alternator working harder and longer charging a larger battery set) that ESS systems were designed not so much to address, but rather to pass a EPA test that if saving fuel was the truly the goal, IMHO could have been better devised, and earn mileage credits.

Off soap box.

 

[tony58]

James thanks for that info what defeat harness did you use and where did you get it, thanks.

 

[AndySpill]

I think this an inportant point when jump starting dual AGM battery JLs with factory setup.

The wait time of keeping the jumper cables on the main battery is extended because time is needed to not simply apply power to the ESS/Aux battery (and the main battery)--which happens because both the main the ESS/Aux battery are connected in parallel at rest...

...but enough power for that ESS/Aux battery to live on its own, separated from the jumper cables.

You see when you cold crank that ESS/Aux battery is for an instant separated from the main battery, meaning it too is separated from the jumper cables, to test its voltage.

Years ago I thought we could get around this limitation by instead hooking up the positive of the jumper cables, not to the positive of the main battery, but N1 in the PDC.

I think Jerry @Jebiruph, the Godfather of all of our understanding here. originally thought this risky, but may have over time come to find this okay. In truth I forget his thoughts on this, hence my tagging him.

 

[Heimkehr]

James thanks for that info what defeat harness did you use and where did you get it, thanks.

Here you go.

 

[rohdawg]

My understanding is it maxes at 14.4V. Is that not correct? What's the source for the 15.0 figure?

Mine was showing this due to an overcharging situation I was having a week or so ago.
Both batteries load tested poorly and were changed out.
I haven’t seen anything over 14.8 since.

 

[tony58]

Here you go.

thank you!!

 

[THAW]

In a perfect world I believe Stellantis would have designed a dual equal size battery system where the batteries periodically switch roles as main an Aux battery.

The more I consider it, the more I think the current design is actually quite good for it's intended purpose. After all, the Jeep disables ESS and warns (perhaps not specifically enough) users when an ESS battery needs replacement. It seems to me most problems (read main battery damage) arise from ignoring the warning - sometimes for a very long time, perhaps mostly out of disinterest in the intended functionality.

To my way of thinking, the main design flaw is: unnecessarily difficult service/replacement access of a wear part.

Sure, the ESS battery could be bigger to increase the replacement interval, but then it'd just be proportionally more expensive to replace.

 

[tony58]

Lots of info out there, how it seems if I leave a trickle charger on the jeep hit the ess off each time and pull the fuse and disconnect the negative cable I should be fine without buying the eliminator with no ill affects, thanks again

 

[THAW]

Lots of info out there, how it seems if I leave a trickle charger on the jeep hit the ess off each time and pull the fuse and disconnect the negative cable I should be fine without buying the eliminator with no ill affects, thanks again

Yes.

Maybe people use the phrase "trickle charger" in a generalized sense, but use a 12V battery charger with an AGM profile.

Regular maintenance charging is the best way to maximize the life of an AGM battery since an alternator effectively only ever "sufficiently" "replenishes" the battery as opposed to properly charging it with bulk, absorption, and float phases.

 

[AndySpill]

The more I consider it, the more I think the current design is actually quite good for it's intended purpose.

I agree Foster. Where I suspect we disagree is on the definition of that intended purpose.

My definition is/was for Stellantis to simply pass the EPA's requirements, as a new vehicle, for being ESS enabled, to qualify under law to advertise more favorable mileage ratings, meet CAFE standards, and avoid massive penalties that consumers would in part have to pay for.

Not as a time tested reliable engine start stop system. Too many people report ESS systems that fail to engage for me to consider it reliable. And as you know, others have already pointed out the issues with connecting two dissimilar size batteries, even of the same type and chemistry, in parallel.

After all, the Jeep disables ESS and warns (perhaps not specifically enough) users when an ESS battery needs replacement.

You appreciate Foster how many people are getting messages that their ESS system isn't ready to engage for battery related reasons, right?

It seems to me most problems (read main battery damage) arise from ignoring the warning - sometimes for a very long time, perhaps mostly out of disinterest in the intended functionality.

That might be a valid point IMO if the warning wasn't so frequent.

To my way of thinking, the main design flaw is: unnecessarily difficult service/replacement access of a wear part.

That has and IMO lacks merits concurrently. If I may, I agree that replacement of the ESS/Aux battery through the side, although the Stellantis service advised procedure, probably wasn't part of the original vehicle specs until the frequency of this change necessitated a procedure that statistically would cost less than going in from the top and a service tech risking damage of expensive PDC components in the process. bjut I find it hard to believe a procedure that has the potential to rip apart plastic rivets, as cheap as they are to replace, was the intended way to replace the battery from the vehcile's original design.

But now with this procedure in place, it really isn't that hard to replace the ESS battery.

Sure, the ESS battery could be bigger to increase the replacement interval, but then it'd just be proportionally more expensive to replace.

..and purchase as a new vehicle, and reduce reported MPG ratings as a smart alternator has to work that much harder to bring a biggercombined battery system to charge. Plus, again, it's not just making the ESS battery bigger, its make it equal size to the main, as most correctly done parallel battery setups are made.

Friends at solar forums would do backflips over such placement of dissimilar sized batteries, even of the same chemistry and type, in parallel.

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