AUX battery delete/bypass - Which method is proper?

[bobholthaus]

BTW, you guys are all freaking genius'. Thanks again for all of this!

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[AndySpill]

How do you reset the IBS ?

The short answer is that you deny it electrical current for a few seconds. The longer answer addresses the fact that many JLs are equipped with two AGM batteries and that in those JLs merely disconnecting the IBS from the negative post of the main battery is a necessary but insufficient step to deenergize it, as it is still receiving power from the ESS/Aux battery.

Two factory black cables connect at the negative post of the main battery as well. One of these cables has at its distal end the body ground on the passenger's front quarter panel near the top of the engine bay.

It is that cable you leave untouched.

The other cable has at is distal end the negative post of the ESS/Aux battery. It is this cable's end near at the main battery's negative post that must as well be disconnected from the IBS, just as sure as the IBS needs to be separated from the negative post of the main battery in order to deny it power and reset it.

 

[JLfromCA]

I’m doing the aux delete by pulling fuse 42 disconnecting the negative battery terminal but I’m actually removing the aux battery completely. Where does the positive aux battery lead go to? I would like to disconnect it at that end also. Thank you.

 

[AndySpill]

I’m doing the aux delete by pulling fuse 42 disconnecting the negative battery terminal but I’m actually removing the aux battery completely. Where does the positive aux battery lead go to? I would like to disconnect it at that end also. Thank you.

https://www.jlwranglerforums.com/fo...ss-which-method-is-proper.123845/post-2589068

...to the Power Control Relay (PCR), to N3 on the Power Distribution Center (PDC)high amp fuses, and the other cable on the Aux battery's positive post to the N1 contact point on the PDC.

 

[bobholthaus]

So I took my Jeep in today; ESS hasn't worked since early Dec. The "battery charging" error has been present. The dealer calls me this morning and says, "both batteries were low; we charged them and then did the load test and they're both fine, come pick it up". In which I politely told him that it hasn't worked for 2 months, and that the vehicle isn't charging the batteries and that now the main battery is dying too. I pressed him (firmly), so he had the porter go drive it. Within 5 minutes the ESS wasn't working again, and now he just texted and told me that both batteries were replaced and they're also replacing the Intelligent Battery Sensor. I asked him to check fuse N3, as my hunch is that it's blown. At this point, I will do the battery delete and call this issue a day.

Lesson: read these forums. Press your dealer when they don't know what they're talking about; we frequently have more data than they do. I appreciate the help of all of you!

 

[THAW]

Guys: Can someone tell me how to "simply" test if N3 is blown? If I take that fuse "array" out (per this video), will it be clear where I can run 12v on one side, and see if it flows through the fuse? I'm not sure why I care at this point, with plans for the battery delete, but I guess I like things to be as "correct" as possible, so I'd like to replace that fuse array if N3 is blown, even if I am not the one to use it currently (same reason ANDYSPILL is recommending I leave all wiring in place, even if I pull the aux battery. Courtesy to the next owner, even if that's years from now!)

If you plan to bypass/delete the ESS/Aux battery, there's not much need to preemptively test the N3 fuse. The bypass/delete is the test, since after it's done the vehicle won't start/run with a blown N3 fuse (assuming N1 and N2 aren't intentionally jumpered).

There's little reason to test an N3 fuse on a functioning vehicle. A blown one quickly reveals itself because the vehicle stops operating.

 

[bobholthaus]

If you plan to bypass/delete the ESS/Aux battery, there's not much need to preemptively test the N3 fuse. The bypass/delete is the test, since after it's done the vehicle won't start/run with a blown N3 fuse (assuming N1 and N2 aren't intentionally jumpered).

There's little reason to test an N3 fuse on a functioning vehicle. A blown one quickly reveals itself because the vehicle stops operating.

Oh crap, I didn’t know this. I don’t recall ever reading this. My Jeep died in Dec and had to be towed to the dealership; my hunch is that that was the day the aux battery shot craps. The dealer let the main battery go dead (the dash was stuck on, the ignition wouldn’t work), and after it went dead and they charged it, the Jeep started. Since that day, the ESS has not worked and the screen said “battery charging”

So, what’s different between having a dead aux battery and taking the ground off for the delete?

And to clarify: if i want to delete but not take the battery out (remove negative and pull fuse 42), I HAVE to have a working N3? Did I miss this somewhere in this thread? Because I’m ready to delete this weekend. Also, does the ignition come on but it just won’t turn over?

 

[THAW]

So, what’s different between having a dead aux battery and taking the ground off for the delete?

The practical difference is a connected dead ESS/Aux battery can cause electrical malfunction and/or damage your main battery.

Whereas, if the ESS/Aux battery is not grounded, it's bypassed and it's health is irrelevant to the Jeep's electrical system.

And to clarify: if i want to delete but not take the battery out (remove negative and pull fuse 42), I HAVE to have a working N3?

Effectively, yes. An electrical path between N2 and N1 is required. Unless modified with a jumper, the stock wiring uses N3 (and thus it's fuse) for that path.

There's currently no reason to suspect your N3 fuse is blown.

 

[bobholthaus]

The practical difference is a connected dead ESS/Aux battery can cause electrical malfunction and/or damage your main battery.

If the ESS/Aux battery is not grounded, it's bypassed - so it's health is irrelevant to the electrical system.



Effectively, yes. An electrical path between N2 and N1 has to exist. Unless modified with a jumper, the stock wiring uses N3 (and thus it's fuse) for that path.

There's currently no reason to suspect yours is blown.

I did arc my high amp fuses one day when I was trying to get access below the PDC before I realized there were two batteries. Also, my ESS hasn’t worked for the last two months and I got the battery charging warning on the dash. Would that be indicative of the aux battery not charging due to a blown N3?

 

[THAW]

I did arc my high amp fuses one day when I was trying to get access below the PDC before I realized there were two batteries. Also, my ESS hasn’t worked for the last two months and I got the battery charging warning on the dash. Would that be indicative of the aux battery not charging due to a blown N3?

Well, with that information, I retract my statement about "no reason to suspect" you have a blown N3 fuse.

However, if you've operated the vehicle regularly for 2 months, there's still not much chance the N3 fuse is blown.

When it's blown, your ESS/Aux battery won't get charged by the alternator. It's around 12Ah, so it would be flattened pretty quickly by various system electronics. At that point, you'd likely experience a bunch of weird electrical issues and/or your Jeep wouldn't start/run.

I still think the best way for you to test it is to do the planned ESS/Aux battery bypass and see what happens. Disconnecting the ESS/Aux battery cable and pulling F42 is quick, easy, and reversible.

 

[AndySpill]

If you plan to bypass/delete the ESS/Aux battery, there's not much need to preemptively test the N3 fuse. The bypass/delete is the test, since after it's done the vehicle won't start/run with a blown N3 fuse (assuming N1 and N2 aren't intentionally jumpered).

There's little reason to test an N3 fuse on a functioning vehicle. A blown one quickly reveals itself because the vehicle stops operating.

In dual AGM battery JLs at least, when you write above "bypassing" the ESS/Aux battery I humbly admit to knowing two ways. One is the fused jumpering of Power Distribution Center (PDC) points N1 and N2 as you write, and the second (or both if you like) is the deenergization, invariably by fuse pull, of circuit 42 in the vehcile, preventing the Power Control Relay from being energized out of its normally closed state to separate the two batteries.

Either or both will fail to isolate the ESS/Aux battery and silently cause any vehicle "requests" for electrical current from solely the ESS/Aux battery to instead go to all batteries, of which only one remains connected (i.e. the "delete" in bypass/delete above)...the main battery.

Given this, I can't see how a blown N3 fuse, which as a result fails to charge an ESS/Aux battery that itself is disconnected from the electrical schematic of the vehicle posses issue.

Maybe N3's demise somehow effects other Nx fuse points.

Maybe I am missing something.

 

[bobholthaus]

I just picked up the Jeep; both batteries were replaced (my low/dead aux battery killed my main battery like it's known to do). I will do the delete by the fuse pull method/remove neg terminal on aux battery. I will let you guys know what happens (give me a couple of weeks to do this).

 

[AndySpill]

Well, with that information, I retract my statement about "no reason to suspect" you have a blown N3 fuse.

However, if you've operated the vehicle regularly for 2 months, there's still not much chance the N3 fuse is blown.

When it's blown, your ESS/Aux battery won't get charged by the alternator. It's around 14Ah, so it would be flattened pretty quickly by various system electronics. At that point, you'd likely experience a bunch of weird electrical issues and/or your Jeep wouldn't start/run.

I still think the best way for you to test it is to do the planned ESS/Aux battery bypass and see what happens. Disconnecting the ESS/Aux battery cable and pulling F42 is quick, easy, and reversible.

In dual battery AGM JLs, an ESS/Aux battery that fails to hold charge, be it because of its own defect, a blown F3 fuse, both, perhaps other causes that don't effect anything but the ESS/Aux battery's ability to charge (e.g. a loose cable to that ESS/Aux battery), in all but early model 2018's without TSB 18-092-19, which will, as described be unable to start/run, what will/should happen is that, yes, the first attempt to cold crank after this will fail, but subsequent attemps at cold cranking will go against the main battery and provided this battery has ample cranking power the vehcile will start and operate, turning the ESS system off and placing an icon in the EVIC (dash) to this effect (a letter "A" with a near circle and exclamation point after it).

Future cold cranks should only take one attempt. The ESS system will remain off until the next, if any, cold crank in which an energized ESS battery is reintroduced into the system.

If fuse F3 is the reason for the ESS/Aux batteries inability to have charge, all the high amp fuses (they are sold as a block, and there are two different parts, one for people with, and one for people without the high capacity alternator package) need to be replaced, but certainly not the entire Power Distribution Center (PDC) of which the high amp fuses are merely one component.

 

[THAW]

Maybe N3's demise somehow effects other Nx fuse points.

Maybe I am missing something.

As I referenced, a jumpered N1/N2 bypasses a blown N3 fuse.

In other cases with a bypassed/deleted ESS/Aux battery, the main battery powers system electronics downstream of N1 through the N3 fuse.

 

[Samal60]

Final follow-up to my saga. 2018 JL 2-door Rubicon 2.0 liter. I thought it was the aux batter but it's an E-torque. It turns out it was the radio that was draining the battery. The only option through the dealer was to trade in the $2,100 stock radio with an $850 + labor/testing charges and loss of my map updates plus 2 weeks in the shop waiting for the new radio. Should have done more research and could have done it myself. Who knew you couldn't drive a Rubicon without a radio?

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