Are the batteries really isolated during ESS stops?

[jebiruph]

Bingo.

The probes were at N1 and N2, and the ground clips were on the chassis. When both batteries are discharging,

Chassis potential > MAIN negative potential > AUX negative potential.

Yes, a dip at N1 should be expected, not because AUX positive is being pulled down, but because chassis ground is being pulled up relative to AUX negative.

I would have mentioned this earlier but you've been raving like a lunatic and I can't figure out what you're talking about most of the time. I didn't want to further muddy the waters.

I'm glad you finally agree with point I've been making all along, that the aux battery voltage pattern on your oscilloscope image follows the pattern of powering the starter. I appreciate the time your are putting into this, but it would have saved a lot time if you would have attributed that to the shared ground wire sooner.

Thanks for your help (not meant sarcastically).

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[jebiruph]

All of this while ignoring documents stating how it works (explaining they are disconnected during initial starter engagement), and voltage tests showing both batteries dropping at the same rate during the ESS stop (showing they are connected during the stop).

Two solid indicators of what's going on. Documents, and evidence through volt meters, all muddied by a scope picture - which will be showing a combination of things happening -
dip due to increased load,
and
dip due to the common ground potential changing after the load of the main is removed

Back to the answer -
No the batteries are NOT isolated during an ESS stop event
Yes, they remain connected until the starter sequence is started
and yes, the PCM can do all of that in proper order.
The batteries are isolated for a quick voltage check of the aux battery during a cold/push button start,
that's it.

You've certainly been posting lots of documents, but if the documents don't agree with what I'm seeing, I have to work through why they don't agree. Especially when we didn't have all this information 7 years ago and the explanation we did have doesn't agree with the documents either.

I reread through all your documents and they make more sense now. My favorite is this one because how detailed it is. Do you have any information on where the connections were made for the three channels?

 

[LowOnCash]

The aux battery does not start the engine...you're going off on a tangent based on a serious misunderstanding of the system.

Well if it does not help to start the engine then why is it there, why are the commons tied together and when the aux battery dies why is there starting problems?

 

[ShadowsPapa]

Well if it does not help to start the engine then why is it there, why are the commons tied together and when the aux battery dies why is there starting problems?

Apparently, from that comment, you don't understand parallel battery circuits.
The grounds AND positives are tied together. That's a parallel battery circuit. Everything shares a common ground, it makes perfect sense to have those connected at all times. Why not tie them together.
As has been explained in this and other threads, it's to protect the electronics, to ensure there will be enough power to keep the truck powered while the crank battery handles the starting circuit.


When the aux dies there MAY BE starting problems like with when the MAIN battery dies.
The auxiliary battery can go bad in such a way as to pull down the other battery, the main battery may go bad in such a way to pull down the aux battery.
There are times when the 2, or 3 battery parallel systems have a bad battery and will prevent even your precious Cummins from cranking. You pull the bad battery out of the mix and it starts fine. Otherwise, it may have no effect.

I've had aux battery go bad in a Grand Cherokee - and was able to jump start it just fine.
Sometimes people don't know what they are doing, how to jump a vehicle (they get impatient) and so on.

 

[LowOnCash]

Apparently, from that comment, you don't understand parallel battery circuits.
The grounds AND positives are tied together. That's a parallel battery circuit. Everything shares a common ground, it makes perfect sense to have those connected at all times. Why not tie them together.
As has been explained in this and other threads, it's to protect the electronics, to ensure there will be enough power to keep the truck powered while the crank battery handles the starting circuit.


When the aux dies there MAY BE starting problems like with when the MAIN battery dies.
The auxiliary battery can go bad in such a way as to pull down the other battery, the main battery may go bad in such a way to pull down the aux battery.
There are times when the 2, or 3 battery parallel systems have a bad battery and will prevent even your precious Cummins from cranking. You pull the bad battery out of the mix and it starts fine. Otherwise, it may have no effect.

I've had aux battery go bad in a Grand Cherokee - and was able to jump start it just fine.
Sometimes people don't know what they are doing, how to jump a vehicle (they get impatient) and so on.

Thanks for the reply - You've got your wires crossed LOL

I'm pretty much up to date on batteries. I design RV lithium systems for most every RV and also provide lithium design for major companies such as Lithionics Battery, Victron and Xantrex.

www.rvvolt.com

Regards - Mike

 

[ShadowsPapa]

Lithium very different from AGM here. It's a lot easier to mix AGM battery capacities than lithium batteries. AGM batteries of different sizes/capacities work more easily together when combined.

The electronics connections were described in detail here, as well as the reason for this system and how it truly works as opposed to how some believe it works.

You've seen systems in other vehicle when you hit the start sequence - crank it over. Lights dim, electronics shut down and some things simply get disconnected.
That's hard on all of the modules involved, electronics fail at power-up, inrush of current, and brownouts are bad and will cause a PCM, BCM and so on to reset.

It ensures the modules maintain enough power, the voltage regulated lighting stays up to snuff, the HVAC fan doesn't get voltage cut to it (causing high amperage draw).

 

[Flanders]

I'm glad you finally agree with point I've been making all along, that the aux battery voltage pattern on your oscilloscope image follows the pattern of powering the starter. I appreciate the time your are putting into this, but it would have saved a lot time if you would have attributed that to the shared ground wire sooner.

Frankly, I couldn't figure out what you were going on about. Rambling 250 word posts without ever answering a question are not an effective communication strategy.

I was trying to get you to figure out for yourself why 3V across a 12V high-current relay means the relay isn't conducting. Horse, water, no drink.

I'm perfectly willing to be proved wrong.

Are we there yet? I think we're there.

 

[ShadowsPapa]

 

[jebiruph]

I guess you have to have a special harness or poke a hole in the wire for C.

 

[jebiruph]

Frankly, I couldn't figure out what you were going on about. Rambling 250 word posts without ever answering a question are not an effective communication strategy.

I was trying to get you to figure out for yourself why 3V across a 12V high-current relay means the relay isn't conducting. Horse, water, no drink.



Are we there yet? I think we're there.

I agree that you are difficult to communicate with. I did answer my own question and then you said you knew the answer all along but didn't want to confuse me.
(edit) I do agree that I did not communicate well in this thread.

Your overall point was correct, but your simple calculations didn't account for all the voltage factors. I think we're done with the battery disposition during the ESS restart discussion. Your oscilloscope images and @ShadowsPapa's docs are very informative.

 

[LowOnCash]

Lithium very different from AGM here. It's a lot easier to mix AGM battery capacities than lithium batteries. AGM batteries of different sizes/capacities work more easily together when combined.

The electronics connections were described in detail here, as well as the reason for this system and how it truly works as opposed to how some believe it works.

You've seen systems in other vehicle when you hit the start sequence - crank it over. Lights dim, electronics shut down and some things simply get disconnected.
That's hard on all of the modules involved, electronics fail at power-up, inrush of current, and brownouts are bad and will cause a PCM, BCM and so on to reset.

It ensures the modules maintain enough power, the voltage regulated lighting stays up to snuff, the HVAC fan doesn't get voltage cut to it (causing high amperage draw).

You're !00% Incorrect - Parallel or series, be it lithium, AGM or flooded, Gel, etc., all work on the same exact principles.

Also note, you can pair two of the "same" or even "different size" batteries in parallel they work fine together, even with different charging protocols. Even with the engine off, if the voltage of one battery is higher than the other battery in parallel, the battery with the higher voltage will then charge the lower voltage battery until both battery voltages are approx the same.

For this same reason, when our small battery loses capacity (as it often does) and its voltage lowers, the large starting battery with its higher voltage tries to charge the smaller defective lower voltage battery, causing the main starting battery to deplete and fail to start the truck.

Bottom line the smaller battery in our Jeeps is only there as a "supplement" for "additional" starting cycles. There's no rocket science, mirrors or smoke in its operation. In simple terms, its just a pair of batteries and a simple electric starter motor.

As I stated in my earlier post, the whole 2nd battery concept is a horrible mistake in design to meet emissions at our expense. No owner really cares about saving a teaspoon of gas with stop & start when your only getting 12-18 mpg. The fix is to delete the Stop & Start protocol and the 2nd battery. If you like Stop & Start, you can delete the smaller battery and install a larger amperage battery using the same group. (In most cases a patch is required to avoid warnings)

Ride Safe - Mike

For those with RV's here is a 51 volt lithium system we recently designed for RV's.

 

[ShadowsPapa]

Bottom line the smaller battery in our Jeeps is only there as a "supplement" for "additional" starting cycles. There's no rocket science, mirrors or smoke in its operation. In simple terms, its just a pair of batteries and a simple electric starter motor.

Biggest crock in this whole thread, or any other thread talking about this system.
You have no understanding of the electronic principals involved or the reasoning behind it - that's apparent.

(In most cases a patch is required to avoid warnings)

Really? What patch? There's nothing needed to avoid warnings.
That's funny - you haven't followed this at all.

No owner really cares about saving a teaspoon of gas with stop & start when your only getting 12-18 mpg.

Hilarious - more proof you are way out of tune with this whole system. Go do some homework. 8 to 10% isn't a teaspoon.

or this same reason, when our small battery loses capacity (as it often does) and its voltage lowers, the large starting battery with its higher voltage tries to charge the smaller defective lower voltage battery, causing the main starting battery to deplete and fail to start the truck.

And what about all of those owners who have a primary battery fail when the auxiliary battery is just fine? Or that have a aux battery fail, and the main battery doesn't fail or "deplete".

This whole thread has been to explain the uneducated on auto-electric systems, or electronics, on the whole purpose or reason for that second battery, why it's there, and what it does NOT do during a restart. The only time the aux battery is involved in starting is during a cold big-button start. Otherwise the smaller battery is disconnected from the starter, and doesn't participate in restarting the Jeep.
This system has been used by other companies - including BMW, Ford, GM/Chevrolet and so on. It's not an invention of Jeep and Jeep wasn't even the first to use it.


From another Jeep forum - a fairly well-known guy out there:

It exists to help protect your Jeep's computer from the surge it gets from starting your engine. Removing it WILL cause damage to the computer over time. This isn't my opinion, this is straight from the engineers at Jeep.

May as well stick with your lithium systems, you have no understanding of this system even after years of us explaining it over and over.

 

[Flanders]

@jebiruph

Imagine you're talking to a guy who clearly doesn't understand some basic principle. The Dunning-Kruger is strong in this one and he mistakenly believes himself to be the most knowledgeable person in the room.

You review the setup and proceed in small steps, each justified by a fundamental principle, hoping to figure out what it is he doesn't grasp. But the guy won't engage at that level. He just insists you're wrong.

What would you do in this (purely hypothetical) situation?

 

[ShadowsPapa]

Then there are those who didn't do well in HS math test scores only because it wasn't possible to "show your work". The answers were correct, but explaining how you got there was impossible. And years later, when a boss or co-worker asks "how do you know this" or can you teach this to me.
No, sorry, I just know it.
I can't explain it well to others, so rely on examples.
It's a very well defined condition, and shown by various video examples - one I recall is a kid given a task and after the deadline passes, he can't even explain how or when he did the task - they see the results, he can't explain how it got there.
You know what you know but can't prove or demonstrate it in a meaningful way.
Along with that comes tons of self-doubt. Looking back in projects done years ago and are very sure you didn't do it, and you can't possibly do it - and yet, there it is. Nope, I don't know how to do that.

 

[Andy29847]

I've been following this thread since it started. I've been tempted to jump in a couple of times. I've resisted thinking that eventually youse guys would reach a consensus. I've lost patience. Here is my 2 cents:

In real life, the JL/JT battery system suxs. It starts with mediocre batteries. It includes an intelligent battery sensor that tell us nothing. It is difficult to diagnose problems when they occur. One battery is hidden on the firewall, below the fuse box. Trips to the dealer for battery problems often result in multiple visits. The benefits of having 2 batteries are miniscule.

All we are really getting from Jeep with their battery system is something to talk about on the internet.

Peace of mind at last! Replaced main battery with a premium H7/Group 94 battery | Jeep Gladiator (JT) News, Forum, Community - JeepGladiatorForum.com

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