Removing AUX battery was actually easy!

[R3TRO]

There has been lots of talk about the aux battery lately so...

I was reluctant to do this after watching many YouTube videos. Some go through the top removing the distribution block. Others remove the entire inner fender liner. And crazy people remove the entire fender (and break all the clips in the process!). I know I could just leave it in place after removing neg cable and fuse 42 pull, but my inner OCD voice kept saying, you have a 15lb paper weight just sitting there doing nothing! So...

I decided to go through the inner fender liner and it was actually quite easy! I did remove the front passenger side wheel first for easier access. But basically you only need to remove a few 10ml bolts. Pull a few plastic clips with a trim removal tool. Then just pull back the liner and you have access to the box, that the aux battery is in, which is held in by 3x bolts. Now drop the aux battery enough to get to the terminals to disconnect. Took maybe 30min tops! You only need to remove enough clips and bolts to fold back the liner, not every single one, fyi!

A few pics...

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[Jmazz]

Nice! I'm going to do it your way once the Aux starts acting up.
I noticed you taped up the positive and left it in the box. The negative i understand but some have routed the positive up to the main - which looks to be a pita to do. Any drawbacks? No error codes?

 

[R3TRO]

Nice! I'm going to do it your way once the Aux starts acting up.
I noticed you taped up the positive and left it in the box. The negative i understand but some have routed the positive up to the main - which looks to be a pita to do. Any drawbacks? No error codes?

I was probably being over cautious and just decided to tape up any bare metal. It wasn't worth the effort to remove the cables, not to mention I still have the option to add an aux battery in the future if I change my mind or sell it.

All I did was pull the neg off the main and taped that up then pulled fuse42. I get no ESS errors and everything works as should.

 

[bcupton]

That’s how I replaced mine! Easy-Peazy

 

[xj884x4]

Just did the same. My OEM batteries on my 2019 (picked up Dec 2018) died in 2020 or 2021, dealer replaced free of charge. Now in Feb2025 either one or both of the dealer replaced batteries died and wouldn't start this morning. ESS is annoying, especially with manual trans, so I decided to bypass it with Fuse 42 and taping and securing the neg wire to the Aux battery. Bought a new Interstate H7 AGM battery to upgrade from my H6 battery, fit in there fine with the plastic spacer thing removed, started right up. Left the old Aux battery in there, not worth the time to fish out the 15lb thing since it is so buried. There is a good YouTube video of a guy removing it via the PDC instead of fender, seemed pretty easy but figured KISS is better than truly deleting it.

Stellantis sucks. Their quality/reliability and design/engineering is terrible. After having a 78 CJ5, 88XJ, 97ZJ, 02WJ, 04WJ, 05TJ, this 2019JL is such a POS in comparison. I only keep it because it is paid for and fun to drive, but the quality and reliability truly suck. As a previous Tier3 supplier automotive design engineer, I can say that there are lots of gaps in the engineering process of creating the JL in terms of fit/form/function and user experience, hopefully all to cost reduction and not incompetence. It will absolutely be my last jeep until they turn things around, even if I have to fully restore my 88XJ as a daily driver.

 

[WillysMeow]

Just bought our 2025 Wrangler Willys and researching all the must do free and cheap mods, this needs done and your pictures and explanation are excellent and to the point, thanks!

 

[Htfan]

Yes, that is the best way to get it done. The surprising thing is that many still want to do it to hard way even though a simpler method is available.

 

[azwjowner]

Thanks for this post. I just removed my aux battery today using this method, and it was easy. To be specific, I only removed two 10mm bolts and the two plastic "Christmas tree" push pins that are next to each other at the very bottom of the rear of the inner fender liner. That was all it took to be able to fold back the liner and access the aux battery.

 

[MidwestJeeper]

Thanks for this post. I just removed my aux battery today using this method, and it was easy. To be specific, I only removed two 10mm bolts and the two plastic "Christmas tree" push pins that are next to each other at the very bottom of the rear of the inner fender liner. That was all it took to be able to fold back the liner and access the aux battery.

Hey man,
Did you do a full delete or did you only take the negative wire out from the main battery's negative post?
I am confused as to which of the 2 wires to pull from the main battery, to do the bypass.

 

[AndySpill]

Hey man,
Did you do a full delete or did you only take the negative wire out from the main battery's negative post?
I am confused as to which of the 2 wires to pull from the main battery, to do the bypass.

The following guidance works on all model year dual AGM battery JLs:

Two factory cables are attached to the negative post of the main battery.

One of those cables, at its distal end connects to the body ground on the passenger's front panel just under the hood. Leave that cable connected.

Remove and tape up the end of the other cable. It is this other cable whose distal end, sight unseen, connects to the negative post of the Aux battery, and where disconnecting this cable at the main battery's negative post prevents that Aux battery thereafter from providing power to, or getting power from the vehicle.

 

[azwjowner]

Hey man,
Did you do a full delete or did you only take the negative wire out from the main battery's negative post?
I am confused as to which of the 2 wires to pull from the main battery, to do the bypass.

I did the full delete, wiring and all. After I removed the main battery and carefully temporarily wrapped up the terminals to avoid hitting anything, even the body, I then disconnected the aux battery. Now that there was no power anywhere, I used a multimeter to confirm which of the two cables coming off the main battery negative terminal went to the ground bolt nearby and which went to the aux battery negative. Once I had identified that, I removed that cable.

My understanding is which physical cable goes to the aux negative has varied throughout the years, so best to trace the cables on your particular Jeep.

 

[AndySpill]

I did the full delete, wiring and all. After I removed the main battery and carefully temporarily wrapped up the terminals to avoid hitting anything, even the body, I then disconnected the aux battery. Now that there was no power anywhere, I used a multimeter to confirm which of the two cables coming off the main battery negative terminal went to the ground bolt nearby and which went to the aux battery negative. Once I had identified that, I removed that cable.

My understanding is which physical cable goes to the aux negative has varied throughout the years, so best to trace the cables on your particular Jeep.

That's certainly an acceptable way to determine the correct cable. Of course it involves first accessing the Aux battery to disconnect its cables whereas as most Aux bypassers leave that battery in place.

Here's some 411 on the cable switch we both referenced.

https://www.jlwranglerforums.com/forum/threads/ess-battery-cable-change.86624/

 

[Rhinebeck01]

Hey man,
Did you do a full delete or did you only take the negative wire out from the main battery's negative post?
I am confused as to which of the 2 wires to pull from the main battery, to do the bypass.

@MidwestJeeper

The cable on the Main's negative side that you need to disconnect and cover will be the smaller diameter cable there. Look close, one black cable is slightly smaller in diameter then the other.

Does not matter what year JL you have.. it is always the smaller diameter cable you would disco.

 

[WXman]

So are you saying that if a guy simply disconnects the smaller of the two negative cables from the main battery and tape it up, and then pull fuse #42, that will effectively remove the Aux battery from the system? No CELs, no ESS function, no issues? And then you just leave the Aux battery in place, and connected pos and neg?

 

[Terrymo]

@MidwestJeeper

The cable on the Main's negative side that you need to disconnect and cover will be the smaller diameter cable there. Look close, one black cable is slightly smaller in diameter then the other.

Does not matter what year JL you have.. it is always the smaller diameter cable you would disco.

Pretty sure when you talk about batteries here you’re supposed to sprinkle in words from your medical background like medial, lateral, distal, proximal, and an occasional longitudinal bifurcation.

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