AUX battery delete/bypass - Which method is proper?

[Sting]

My Jeep's (21 JLUR 2.0T non-eTorque) batteries died from the extreme cold, so Im going to have to replace one or both batteries. Im considering removing the small AUX battery (for ease of future maintenance/preventative maintenance) by connecting the AUX battery's positive cable to the main battery's positive terminal. If I do so, will start/stop still work as Jeep intended or do I have to disable start/stop (with a Tazer, etc.) without an AUX battery? Do I need to also disconnect the AUX battery's negative cable from the main battery's negative terminal? Will I still need to pull the fuse (F42 PCR CTRL FEED -ESS) ?

Which method is the proper way to delete/bypass the AUX battery? Multiple sources say different things. AUX Negative wire vs AUX Positive wire, Fuse or no Fuse:

• jumperless-aux-battery-bypass -- https://www.jlwranglerforums.com/forum/threads/jumperless-aux-battery-bypass.95945/
  • Recommends:
    • Pulling fuse F42
    • Disconnecting AUX Negative cable from main battery's cable.
    • No mention of the AUX battery's positive cable.
• Jeep Gladiator (and JL) Auxiliary Battery Bypass (Single Battery Conversion) No More Dead Batteries --
  • Recommends:
    • Attaching AUX Positive to main battery's positive
    • He appears to leave AUX's negative attached to main battery's negative cable.
    • No mention of fuse F42
• Genisis Offroad --
  • Recommends:
    • Attaching AUX Positive to main battery's positive
    • He appears to leave AUX's negative attached to main battery's negative cable.
    • No mention of fuse F42

Sponsored

 

[TheNewGuy]

If you're going to completely remove the AUX I suppose you can leave both terminals connected to the main as long as you isolate and wrap the connections on the AUX side. Or you can just remove the entire harness. If you leave the bad AUX where it is, just disconnect the negative. You'll want to pull the fuse in both instances.
Go with the info you read on this forum
ESS will still work off the main battery unless you disable it with a Tazer or a SmartStartStop kit.

 

[AndySpill]

My Jeep's (21 JLUR 2.0T non-eTorque) batteries died from the extreme cold, so Im going to have to replace one or both batteries. Im considering removing the small AUX battery (for ease of future maintenance/preventative maintenance) by connecting the AUX battery's positive cable to the main battery's positive terminal.

This is not wrong and it is not required. Such a cable does absolutely nothing going from the same battery terminal to the same battery terminal and the KISS principle would suggest its removal or the insulation of its loose end if you want to keep it in place.

If I do so, will start/stop still work as Jeep intended or do I have to disable start/stop (with a Tazer, etc.) without an AUX battery?

It is a busy day for this question. The short answer is that removal of the ESS/Aux battery and operation of the ESS system are two independent things that have nothing to do with each other except if you DON'T disconnect Fuse 42 on (i.e. you) dual AGM battery JL's (you) that don't have TSB 18-092-19 (not you). Only the earliest of 2018's don't have this software upgrade.

If you don't disconnect Fuse 42 and you don't fused jumper N1 to N2, but you do disconnect the Aux battery then your first crank will fail as no ESS battery will be found. But subsequent cranks will be attempted off the main battery and the vehicle will turn on the ESS off in the EVIC for you.

If you pull Fuse 42 and/or implement a fused jumper between N1 and N2, either task (or both redundantly) will not turn off ESS. You will have to do it with a button push or buy tech to do it for you. Disband any notion that removing and ESS battery turns off the ESS system. They are independent with this exception of not pulling Fuse 42 or fused jumpering.

People can run ESS with one or two batteries, or no ESS with one or two batteries.

I do recommend you turn ESS off. There are rare situations where running ESS off of just the main battery could find you "sawing off the tree limb you're sitting on."

Do I need to also disconnect the AUX battery's negative cable from the main battery's negative terminal? Will I still need to pull the fuse (F42 PCR CTRL FEED -ESS) ?

The single cleanest way to disable the ESS/Aux battery IS (not if) to pull the black cable off of the main battery's negative post whose other end leads to the negative post of the ESS/Aux battery and then insulate the end of this cable. Two factory cables connect to the main battery's negative post. One of them has as its other end the body ground at the front passenger's quarter panel just under the hood. Leave that cable connected.

It is the other cable that gets disconnected at the main battery's negative post.

If you do not pull Fuse 42, as mentioned, your first attempt to crank will fail, but subsequent ones will succeed provided your main battery has ample cranking power, as your 2021 is smart enough to know that if it finds no, or a dead ESS/Aux battery, to on the next crank, attempt it only off the main battery. If successful that's were, on the first try thereafter it will continue to crank from only the main batttery, putting the ESS off light in the dash. I don't recommend this because I authored a post on what could be bad about this, and the father of all of these techniques: fused jumper and Fuse 42 pull, @Jebiruph said you don't want to deliberately turn the ESS off light on as its illumination by the vehicle in other circumstances is a tell tail sign of other issues that might be missed if the light is already on.

So, while pulling Fuse 42 is not required, I recommend it if you take the ESS battery out of the picture, or, if you prefer, use the older technique of fused jumpering post N1 to N2 in the PDC.

Which method is the proper way to delete/bypass the AUX battery?

I think the Fuse pull is cleaner. That said, they fused jumper or the fuse pull both do the same thing in different ways, this is, prevent the cables that lead to the factory ESS battery (whether connected or not) from ever being isolated. Fuse 42 pulled prevents a relay from being energized to separate the batteries. The fused jumper (alone) allows that separation but the fused jumper permanently shorts the two batteries together permanently and prevents that relay being energized from being able to separate the batteries.

Multiple sources say different things. AUX Negative wire vs AUX Positive wire, Fuse or no Fuse:

• jumperless-aux-battery-bypass -- https://www.jlwranglerforums.com/forum/threads/jumperless-aux-battery-bypass.95945/
  • Recommends:
    • Pulling fuse F42
    • Disconnecting AUX Negative c
    • Disable from main battery's cable.
    • No mention of the AUX battery's positive cable.

Do the above, don't worry about the positive cable on the Aux battery. You have broken the circuit and need not worry beyond this anyone more you need to worry that a light bulb might turn on just because one (but not both) of its cables are disconnected.

• Jeep Gladiator (and JL) Auxiliary Battery Bypass (Single Battery Co
• nversion) No More Dead Batteries --
  • Recommends:
    • Attaching AUX Positive to main battery's positive
    • He appears to leave AUX's negative attached to main battery's negative cable.
    • No mention of fuse F42

You can break the connection between the batteries by disconnecting either the negative or positive terminal, both. This guy did it with the positive and probably didn't mention how he prevented the two battery cables from being isolated, or chose the deliberate ESS off message in the dash.

Disconnect the batteries with the negative ground cable, okay? It's just cleaner.

• Genisis Offroad --
  • Recommends:
    • Attaching AUX Positive to main battery's positive
    • He appears to leave AUX's negative attached to main battery's negative cable.
    • No mention of fuse F42

I don't know if Shane's advice above was in colloboration with the installation of his kit, in which case all bets are off, or something else. My guess, since you claim he never mentioned Fuse 42 or fused jumpers is you were watching advice that doesn't pertain to you unless you also buy his kit. It is a wonderful product for overlanders. If that's not you, save your money.

 

[Hard Rock Jeep]

Questions for AndySpill. First, your explanations are terrific. Knowing the why is usually part of the fun working on Jeeps. This issue is not fun.

So, what is the downside to leaving batteries, terminal posts and fuses just as they are and using a wiring harness modification to turn off the ESS?

Is there an upside?

 

[Samal60]

Hi all. New guy here, so I hope this is the proper thread.
I have a 2018 Rubicon 2dr 2.0 liter bought new in 2019 all stock. The original batteries went dead in the cold weather yesterday. I figured I would bypass the aux by pulling the #42 fuse and disconnect the ground and tape it up, then replace the main battery. Imagine my surprise when I found there was no second ground on the battery and no fuse 42!
There is definitely a start/stop on it and it gave messages about aux unavailable until the battery is charged the day before it died. I have not been able to find any other variations in this or other forums or on youtube. Any advice would be appreciated, even if it's to tell me I'm foolish and overlooked something simple.

 

[JLfromCA]

Hi all. New guy here, so I hope this is the proper thread.
I have a 2018 Rubicon 2dr 2.0 liter bought new in 2019 all stock. The original batteries went dead in the cold weather yesterday. I figured I would bypass the aux by pulling the #42 fuse and disconnect the ground and tape it up, then replace the main battery. Imagine my surprise when I found there was no second ground on the battery and no fuse 42!
There is definitely a start/stop on it and it gave messages about aux unavailable until the battery is charged the day before it died. I have not been able to find any other variations in this or other forums or on youtube. Any advice would be appreciated, even if it's to tell me I'm foolish and overlooked something simple.

you have a e torque model. Your second battery is a 48 V located under the jeep.

 

[Samal60]

you have a e torque model. Your second battery is a 48 V located under the jeep.

Thank you! I'll do some more homework.

 

[Terrymo]

Thank you! I'll do some more homework.

Etorque battery

 

[Samal60]

Thanks again, but this way over my head now. I replaced the main battery but things are getting worse. Now there's no heat, stereo, or navigation and the screen keeps rebooting. Probably ruining the new battery, going to put a trickle charger on it. My local mechanic doesn't know how to deal with it. Making an appointment with the closest Jeep dealer (1/2 hr away).

 

[Samal60]

Just following up if you all are interested... The dealer say I have neither an aux battery or E-torque, I have a "generator that powers the start/stop and aux electronics". We also discussed the supposed 8yr/80k warranty on the E-torque 48v power pack. He says that is only for hybrid vehicles.

B. Parts Covered for 8 years o r80,000 miles If your vehicle has one of the following parts,
this Federal Emission Warranty covers that part for a period of 8 years or 80,000 miles, whichever occurs first, calculated from the start of the Basic Limited Warranty asset forth in Section 2.1E. The covered parts are:
•Belt Driven Hybrid Starter Generator
•Catalytic Converter
•Powertrain Control Module
•PowerPackUnit-48Volts

I'm seriously concerned what this is going to cost to fix it.

 

[JLfromCA]

Thanks for the update. As usual, the dealer is clueless, if it has a generator it has E torque. The standard ESS with the aux battery will have an alternator. All non 392 JL jeeps have either the aux battery or etorque. There is no other available powertrains

 

[AndySpill]

Thanks again, but this way over my head now. I replaced the main battery but things are getting worse. Now there's no heat, stereo, or navigation and the screen keeps rebooting. Probably ruining the new battery, going to put a trickle charger on it. My local mechanic doesn't know how to deal with it. Making an appointment with the closest Jeep dealer (1/2 hr away).

The fuses in the PDC (Power Distribtuion Center), that black box (literally) on top of the engine space, near the passenger's seat, needs to be checked, particularly if memory service me correctly, point N3 in the High Amp Fuse bus (the driver's side of the PDC). If that fuse is shot the battery I believe can't charge.

If I am correct you get a new high amp fuse bar (an addition to trying to determine why it shorted--it can happen during a battery replacement if you touch cables to the wrong places.) I believe there are two different high amp fuse bars ones depending on whether you have the heavy duty alternator or not. The PDC, a much more expensive component of which the high amp fuses are a part, need not be replaced.

 

[Samal60]

Another update: I had previously registered at Jeep.com, so I used their chat program to ask about the 8yr/80k warranty and they confirmed that if it is indeed E-torque system it is still covered. They will coordinate with the dealer I took it to and verify what the problem is.

 

[OldGuyNewJeep]

The dealer say I have neither an aux battery or E-torque, I have a "generator that powers the start/stop and aux electronics".

 

[THAW]

Such a cable does absolutely nothing going from the same battery terminal to the same battery terminal and the KISS principle would suggest its removal or the insulation of its loose end if you want to keep it in place.

I'm not sure I agree. To me KISS would indicate keeping as much of the factory wiring intact (as in not destroyed) as is readily possible and keeping positive terminal connectors as robustly protected as possible.

The aux positive wire terminal connector crimps around 2 wires, one to N3/PCR and the other to N1. Attaching the aux battery cable terminal connector to the main battery terminal effectively jumpers N1/N2 and bypasses the PCR. Doing so also helps prevent the stock terminal connector between N3 and N1, which is exposed when the aux battery is removed, from shorting (better than wrapping it in electrical tape and leaving it floating around the battery tray, anyway). Granted, this arrangement creates an extraneous connection between the main battery positive terminal and N3 (through the PCR), but that seems worth the tradeoff of avoiding permanently altering the factory wires/looms/connectors.

It seems to me the advice to disconnect terminal connectors and insulate them is applied to the aux battery positive terminal connector because it works and mirrors the way it's often done for the aux negative terminal connector at the main battery when the aux battery is (for convenience) not removed, as opposed to it being the best way to arrange/bypass connections when the aux battery is removed.

I don't know if Shane's advice above was in colloboration with the installation of his kit, in which case all bets are off, or something else. My guess, since you claim he never mentioned Fuse 42 or fused jumpers is you were watching advice that doesn't pertain to you unless you also buy his kit.

The Genesis dual battery system installation recommendation jumpers N1/N2 by attaching the aux battery cable terminal connector to the main battery positive terminal (as I described above). There's no mention of fuse F42 because the PCR is bypassed so the relay closed/open state is irrelevant. The recommendation isn't related to anything specific about the functionality of the Genesis system, it's because the system deletes the original aux battery and it's a clean way to manage (or "groom" as Shane would say) the stock battery cables.

Sponsored