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Auxiliary Battery Jump

jebiruph

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I'll have to verify the layout- which cable is which - on my 2022.
They LOOK exactly the same - same studs and stud sizes, two cables, one bolted to the IBS and the other bolted to the first via the taller stud, but can't say if they switched them around as to which one is the chassis ground and which is the aux battery ground.


1669156568397.png
The body ground cable is a thicker cable than the aux battery cable, or so I've heard.
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The body ground cable is a thicker cable than the aux battery cable, or so I've heard.
You almost have to remove some of the factory wrap to tell for sure which is "thicker", and then check the insulation of each. I've got wires of smaller gauge (higher numerically) that are actually thicker than wires of a lower numerical gauge, so I'm not about to go by the feel of these with the wrap on them.
It would make sense - because the charging current and load off the aux battery isn't about to be anything near what the crank battery handles.
 

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I'll have to verify the layout- which cable is which - on my 2022.
They LOOK exactly the same - same studs and stud sizes, two cables, one bolted to the IBS and the other bolted to the first via the taller stud, but can't say if they switched them around as to which one is the chassis ground and which is the aux battery ground.


1669156568397.png
I had my PDC off when I did my Aux switches as well as the entire battery tray to get the grommet nippe.....the cables didn't make sense based on the videos I was watching....which were for 2020s. I'll see if I can find the link.
 

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When things are working normally, both batteries are connected together. You can't have one dead without pulling from or being a load on the other. That's why when the aux battery goes bad, it kills the main battery as well. And when you charge at the main battery, the aux battery also gets that power from the charger.

I stole this image from another post here - you can see the green is the path of power from and between the batteries.
The negative are tied together very directly - aux battery (which feeds the system electronics when the ESS, or electronic stop/start is active) is connected to the terminal that goes on the main or crank (runs the starter more directly)
So ground is really closely tied, negative are tied together at the main/crank battery (-) and to the body ground.

The positive are also tied together. The positive from the main or crank battery is connected to N2 and through N3 down to the PCR which is a relay, then to the aux battery positive. So you can't apply power to the main battery without also applying power to the AUX battery because it's connected - follow the green dashed line.

Many of us have had the aux battery go bad - and what it can do, and often does, is drain the main battery. They are connected together - + to + and - to -.
If you put a load on one, you drain both.
When you start the vehicle, yes most of the "power" to the starter comes from the main or crank battery, but some also from the aux battery.

If you put a volt meter on the aux battery, it would also drop when cranking.

Putting a jumper from your main or crank battery + means that if that aux battery has a problem, say it's shorted, it will draw down your main battery as well.

If it takes a jumper to make things work, I'd be getting it fixed pronto. You don't know what caused the aux battery to "die" and it's very possible it will take the main battery out with it - it did in the case of one of our Jeeps. I kept jumping it to get my wife to where she wanted to go and finally....... it just wouldn't start back up as the aux battery killed the main battery.
I'd be checking the high current fuses as well.

What they were doing "got them by" but I'd have been really concerned with that aux battery tied directly like that to the main during normal operation.


underhood battery power.PNG
Is the upper negative wire shown at the diagram at the crank battery the aux battery ground? I don't want to tear into the cable connections to determine that if I can help it.
 

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Is the upper negative wire shown at the diagram at the crank battery the aux battery ground? I don't want to tear into the cable connections to determine that if I can help it.
The diagram is representative - it appears at some point there was a change as to which cable was which, but in this picture - the cable connected to the other cable via the tall stud is the auxiliary battery ground.

The cable still on the IBS in the pic below goes to chassis grounds.

Jeep Gladiator Auxiliary Battery Jump 1669160940577


It would be pretty easy to determine- remove the cable as I've shown (just a single nut (12mm wrench) holds the cable in place.
A volt meter on the positive post of the crank battery and the ground stud on the fender would show 12v if you removed the aux ground cable.
 

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56cbr600rr

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Another issue with my buddies Gladiator, we did the one battery swap to the Walmart battery and it still says ESS not work and pull over. Normal?
 

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Another issue with my buddies Gladiator, we did the one battery swap to the Walmart battery and it still says ESS not work and pull over. Normal?
Sounds like you need to either replace both batteries, not just the aux, or give the main a good charge?
 

56cbr600rr

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Sounds like you need to either replace both batteries, not just the aux, or give the main a good charge?
Possibly. We're at work, so did not charge the new battery. Right from walmart shelf into the Gladiator.
 

ShadowsPapa

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Possibly. We're at work, so did not charge the new battery. Right from walmart shelf into the Gladiator.
Never put in a new battery without charging it first.
Always charge a battery before putting it in.

There are, as I've said before, at least 2 dozen reasons ESS may not work.

Another issue with my buddies Gladiator, we did the one battery swap to the Walmart battery and it still says ESS not work and pull over. Normal?
No, not normal.
If it's saying pull over, you have some more serious issues that are preventing ESS from working - including engine issues and more.

Always charge a battery before installing.
For all you know that battery was half charged, at under 11 volts. That can cause issues.
Walmart, especially, a battery can sit on a shelf for weeks or months and due to normal self discharge, go way down before it's purchased.

I'm unsure why there's a lot of resistance of having complex issues looked at diagnosed by pros. These days, even a "common misfire" can be caused by many dozens of different things from physical engine damage to the PCM not learning the crank and cam relationship to O2 sensor issues and more.
My bet is the ESS not working is a symptom of a greater issue, it's like pain - something is going on and masking the pain with aspirin can mean later the cancer is inoperable.

In any case - best bet is:
Pull the ground cables off, separate them.
Charge the AUX battery using a good AGM charger. Let it run however many hours it needs to go through all phases. Stopping it because it's too inconvenient or taking too long means you don't have it properly charged and need to go back to step 1.

Charge the main battery with a good AGM charger - again, don't stop it until the charger says it's done. (10 amp charger at least is best)

While this is going on, make sure the IBS is disconnected and set aside for at least 10-15 minutes or so - or while the batteries charge.

Then finally put it all back together AFTER checking to see if the main battery actually does charge and holds that 12.7 volt full charge after sitting disconnected for a couple of hours.

Not doing all of this is just chasing your tail. You can't skip these steps and then wonder why no one can figure it out.
Gotta make sure both batteries are good, and both batteries are fully charged.
Skipping any of this means people are tossing spit wads at the wall to see what sticks - guesses without anything to go by. Can't solve a crime without at least some clues.
 

56cbr600rr

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So... I like to update Maybe it can help others...

You know how they say start with the easy and obvious... Well..

As posted he had misfiring issues. Was resoved with two new heads, cams, etc...

Electric problem started afterr they did the second head...

Thought it was batteries.. So did the conversion to one battery with one new one. Did not fix it, he went back to the stock set up with two new batteries... Still no-go.

Long story short, cable very very loose on the alternator and assuming the dealer might've loosened it one of the times they were working on it..


anyways, almost a week not and he says its all good.
 

ShadowsPapa

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Loose or poor electric connections cause more issues than people realize. I have corrosion develop on one of the clips on my test bench - goes to a battery for testing alternators.
I hooked everything up, flipped the switch to power things up, turned o the electric motor to drive the alternator and voltage spiked instantly. Shut it down fast, what the heck? Bad ground connection - the regulator circuit was not reading actual voltage and assumed "we need MORE" so pretty much full-fielded the alternator.
Simple ground connection - looked ok, took it apart, cleaned up and reconnected, settled to exactly where it should be. A bit of voltage drop can wreak havoc.
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