Aux Battery Cables

[Als@Ohio]

My 2018 JLU Sahara may be a bad unicorn.
After doing the AuxBatt NEG cable pull, and Fuse 42, pull, it continues to do the "Electrical Storm". And, worse bummer, I got the latest PCM update TSB: 18-039-22. Which included an ABS upgrade.

Dealer charged over $250 for that. I guess only safety TSBs are free. But how is "Electrical Storm" not a safety issue?

Dealer suggested may be CAN bus issue. Which I suspect is a honey pot for the Dealer without any value to me.

Anyone out there ever fixed a defective CAN bus?

Open the glove box. There is a multi wire green connector. That is a CANBUS block. Known to crap out and light up the warning lights. Available from MOPAR & Amazon

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[mbrose1994]

[QUOTE="VKSheridan, post: 3152412]
As for CANBUS, ... electrical anomalies.
[/QUOTE]
Thank you for the specifics, they give me a direction to try. Yes, may not fix issues, but these offer some potential better than a Dealer soaking me while saying they don't know either.

 

[GabeBoyTheGreat]

1. N3 is only used to charge the aux battery. It is connected to the main battery through a 150a fuse, and connects to the aux battery through the normally closed power control relay.
2. Correct.
3. There is no reason to jump N2 to N3, they are both connected to the main battery, N2 directly, and N3 through a 150a fuse. So N3 is already powered 100% of the time, unless the 150a fuse is blown. If you meant N1 jumped N2 or N3, (aux battery always connected to the main battery) the only fallout could be overcharging of the aux battery if it is left in place. If the aux battery is removed, no issues.

Can you help clarify something for me? I currently have my fender flare removed, so I am trying to take this opportunity to perform the AUX battery delete.

My understanding is that at bare minimum, the AUX battery negative cable should be removed/isolated from the main battery terminal, and then I will need to pull the F42 fuse.

However, this assumes I am leaving the AUX battery in the vehicle. My preference is to remove the AUX battery entirely. So what additional step(s) is needed to do this? It sounds like I could jump N1 to N2/N3, but I have also heard that you can connect the AUX positive cable directly to the main battery positive post? Is this accurate?

 

[VKSheridan]

Can you help clarify something for me? I currently have my fender flare removed, so I am trying to take this opportunity to perform the AUX battery delete.

My understanding is that at bare minimum, the AUX battery negative cable should be removed/isolated from the main battery terminal, and then I will need to pull the F42 fuse.

However, this assumes I am leaving the AUX battery in the vehicle. My preference is to remove the AUX battery entirely. So what additional step(s) is needed to do this? It sounds like I could jump N1 to N2/N3, but I have also heard that you can connect the AUX positive cable directly to the main battery positive post? Is this accurate?

Remove the auxiliary battery.
Tape off the cable ends that were once attached to the auxiliary battery or totally remove them at the other end.
Remove Fuse 42.
You don’t need to mess with the N-Fuses.

Peace

 

[AzCoronaDog]

Remove the auxiliary battery.
Tape off the cable ends that were once attached to the auxiliary battery or totally remove them at the other end.
Remove Fuse 42.
You don’t need to mess with the N-Fuses.

Peace

Removing the aux battery, taping the cables off and removing fuse 42 will work fine.
This works because N1 will always be powered by N3 running through the power control relay and back through the aux battery cable to N1. The relay is normally closed (needs power to open), and with F42 removed, will never open. You will see ESS not available messages on the dash, but they can be ignored.

However, if you remove the positive cable that runs from N1 to the aux battery (and joins the cable running to the power control relay), you will need to add a jumper from N1 to either N2 or N3 to keep N1 powered. This is why the simplest fix is to just leave the positive cables in place and tape the ends to prevent any possible short to ground. The aux negative cable doesn't matter, as long as it cannot short to the positive cable.

The key point is that N1 needs to to powered 100% of the time. With the stock aux battery setup, it gets powered by the main battery when the normally closed power control relay is closed (ESS is not in the stop mode, relay not powered), or the aux battery when the relay is open (ESS is in stop mode, relay is powered).

If for some strange reason you want to remove the aux battery but still have ESS operative, a jumper from N1 to N2 or N3 and leaving fuse 42 in place is the solution. The aux cables can then be removed. The relay does't come into play, but the computer will notice if F42 is not there.

 

[VKSheridan]

Removing the aux battery, taping the cables off and removing fuse 42 will work fine.
This works because N1 will always be powered by N3 running through the power control relay and back through the aux battery cable to N1. The relay is normally closed (needs power to open), and with F42 removed, will never open. You will see ESS not available messages on the dash, but they can be ignored.

However, if you remove the positive cable that runs from N1 to the aux battery (and joins the cable running to the power control relay), you will need to add a jumper from N1 to either N2 or N3 to keep N1 powered. This is why the simplest fix is to just leave the positive cables in place and tape the ends to prevent any possible short to ground. The aux negative cable doesn't matter, as long as it cannot short to the positive cable.

The key point is that N1 needs to to powered 100% of the time. With the stock aux battery setup, it gets powered by the main battery when the normally closed power control relay is closed (ESS is not in the stop mode, relay not powered), or the aux battery when the relay is open (ESS is in stop mode, relay is powered).

If for some strange reason you want to remove the aux battery but still have ESS operative, a jumper from N1 to N2 or N3 and leaving fuse 42 in place is the solution. The aux cables can then be removed. The relay does't come into play, but the computer will notice if F42 is not there.

Good points.

Whats funny Jeff is my ESS operates normally with my auxiliary battery removed and nothing touched on N1, N2 or N3.

I did not remove my cables as I figured the next buyer might be a masochist and want to try again with the auxiliary battery. Maybe if I stripped them off the PCM, the results different but that’s my set-up.

I do use a Start/Stop Eliminator that prevents defaulting that feature energized but ESS works no different than when I had the lil’ battery installed.

 

[AzCoronaDog]

Good points.

Whats funny Jeff is my ESS operates normally with my auxiliary battery removed and nothing touched on N1, N2 or N3.

I did not remove my cables as I figured the next buyer might be a masochist and want to try again with the auxiliary battery. Maybe if I stripped them off the PCM, the results different but that’s my set-up.

I do use a Start/Stop Eliminator that prevents defaulting that feature energized but ESS works no different than when I had the lil’ battery installed.

At least according to how my '24 is wired, if you just removed the aux battery with no jumpers, then if ESS goes into engine stop, the power control relay will get engaged and open, disconnecting N3 from N1, and N1 will be unpowered, and things will not work. If you pulled F42, then the relay can never open, and all is well.

Not sure how readable it will be, but I inserted the 2024 battery wiring diagram as a .jpg.
The original diagram in this post is not 100% technically accurate, as F42 is actually on the input to a relay on the power distribution center (fuse box) circuit board (not a replaceable one), that sends power to the bigger power control relay, which connects N1 to N3, connecting the aux and main batteries. I assume this arrangement is because the powertrain control module sends ground to the PCB relay, which sends hot to the power control relay, which opens it and disconnects the main and aux batteries.

 

[VKSheridan]

Interesting. I wonder if they changed up things since the 2020 model years. Either that or many of us have a defective relay always engaged. You’ve triggered my curiosity……Cheers!

 

[AzCoronaDog]

Interesting. I wonder if they changed up things since the 2020 model years. Either that or many of us have a defective relay always engaged. You’ve triggered my curiosity……Cheers!

It is an unusual 'normally closed' type relay, meaning N3 (fused main battery power) is connected to N1 (aux battery output\power for all the important stuff) until it gets powered on by the powertrain control module (PCM).
Pulling fuse 42 keeps that relay from ever disconnecting N1 from N3, and everything stays powered.

I wonder if there is ever a scenario when the ESS goes into Stop mode without powering on that relay? I wouldn't think so, because that is what this setup was designed for, but the PCM can do whatever it is programmed for... (And we all know some of the programming does not always make sense!)

 

[mbrose1994]

1. N3 is only used to charge the aux battery.

Meaning, to accomplish total isolation of AuxBatt:

• Disconnect the AuxBatt POS cable end from the N3 terminal.
• Disconnect the AuxBatt POS cable end from the N1 terminal.
• Disconnect the AuxBatt NEG cable end from the PrimBatt NEG terminal
• Jump N2 to N1.

Results:

• PrimBatt is free of any pull down effect from AuxBatt.
• ESS continues to function as designed, ie, can disable by dash button each drive time.

Am I missing any understanding?

 

[ScotM]

Meaning, to accomplish total isolation of AuxBatt:

• Disconnect the AuxBatt POS cable end from the N3 terminal.
• Disconnect the AuxBatt POS cable end from the N1 terminal.
• Disconnect the AuxBatt NEG cable end from the PrimBatt NEG terminal
• Jump N2 to N1.

Results:

• PrimBatt is free of any pull down effect from AuxBatt.
• ESS continues to function as designed, ie, can disable by dash button each drive time.

Am I missing any understanding?

I got a nice cable and jumper N1 to N3, since it was open after removing everything. I also removed fuse 42 and got an auto stop eliminator

 

[mbrose1994]

I got a nice cable and jumper N1 to N3, since it was open after removing everything.

Very glad you replied, and confused about N1 to N3.
I thought:

• N3 is exclusively used to charge the AuxBatt (AzCoronaDog: thread post #29).
• And N1 is direct power from AuxBatt.

So, a jump from N1 to N3 is connecting the AuxBatt POS terminal to itself?

Also, I got a very nice 6 inch jump cable (double eye ends) to do N2 to N1.
BUT . . . , now have to discover what size NUT fits the terminal posts to piggy back on top.

Metric? Size? Pitch? Can you share those details?

 

[ScotM]

the high capacity fuse array gets power because they are electrically connected, so n1 to n2 or n3 will give the same result, i chose M2’s because it is fused from n1, and will offer protection if something goes awry .1/4” or m6 for size

 

[Mguy]

This thread is a mess and probably confuses more than it helps. I don't believe any puppies will die if it is deleted.

The N load studs, except at the N1 terminal, get power from the main battery connection to N2 and from the placement of the high amp fuse array. The N1 terminal distributes power to most of the Jeep's loads, including those essential for operation. N1 gets reliable power when,

1) the stock aux battery positive cabling is kept in place (regardless of whether the aux battery is connected or not), the fuse at N3 is maintained, and F42 is removed, or

2) a high amp jumper is installed from N1 to N2, or to any other N stud where the fuse is intact, or to a stud on the main battery bus.

The Jeep is metric. The N studs are M6 standard threading. 1/4 inch nuts sometimes work on M6 threads, but their use is not good practice. (Nor is it good practice to think of nuts and studs as conductive and part of the electrical connection, but that's another story).

 

[AzCoronaDog]

Very glad you replied, and confused about N1 to N3.
I thought:

• N3 is exclusively used to charge the AuxBatt (AzCoronaDog: thread post #29).
• And N1 is direct power from AuxBatt.

So, a jump from N1 to N3 is connecting the AuxBatt POS terminal to itself?

Also, I got a very nice 6 inch jump cable (double eye ends) to do N2 to N1.
BUT . . . , now have to discover what size NUT fits the terminal posts to piggy back on top.

Metric? Size? Pitch? Can you share those details?

N2 and N3 both connect to the main battery - N2 is direct by cable, N3 is from N2 but has a 150a fuse.
N1 connects directly to the aux battery.

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