3.6L ESS Aux Battery Bypass

RubiRob

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I'd say lower the gauge a bit (i.e. use thicker cable) at 40amps or down the amps to 30 for 10 gauge wire, or buy one of these:

https://www.amazon.com/gp/product/B000CZ2Z92/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Also--if you want to run one battery I'd recommend that you don't allow ESS to engage. The reason I say this is because ESS may remain on too long thinking the ESS battery (really now your main and only battery with the fused wiring) is chock full of current and that your main battery, which provides the majority of the current for post ESS event engine cranking, is sitting quietly behind the scenes ready to jump in and energize the engine crank, when in fact it is this main and only battery that is getting depleted during ESS events that may drop too low for a successful post ESS engine crank.

Then again it may not. But the 3.6L was designed and calibrated based upon two batteries. Sure, other vehicles run ESS with one battery but the thresholds for when an ESS event terminates because the voltage has dropped too low may be more aggressive in the 3.6JL than in other one battery ESS systems. The Wrangler may push limits with the two battery design that other one battery ESS vehicles don't.
Just got what you recommended, a 10G inline fuse holder with 40a fuse. Going to get it going today. I don't need ESS to work, I just wanna see if my battery finally gets charged up enough so I can point to my AUX as faulty, even though Orielly's said it was fine. When ESS finally engages for me the voltage starts at 12.8 and drops 0.1v every other second. Im usually down to 11.8v by the time the light turns green. If not, oh well. It will still be good to have in case of emergency and it was only $9.

tempImagevRveh2.png





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Toycrusher

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ess bypass simple 2a.PNG


edited 1/12/19 with updated diagram

In case the other diagrams aren't clear, here's a simplified diagram to emphasize how the batteries are connected in parallel through the PCR. A bad Aux battery seems to cause issues with the Aux battery powered systems, this shows the bypass jumper connecting the Main battery to the Aux battery powered systems.
Shame on me for not reading the other 27 pages in the thread first...
But would it not be ideal to run a battery disconnect switch in the jumper lead with the fuse? That would save the trouble of physically removing the cable connection or pulling the fuse which is not ideal either as a fuse holder has a limited number of times a fuse can be removed before losing its clamping force.
Currently I have a dying main battery but the aux is covering starting duties. The built in isolator is keeping my aux hot but I'd like to just pop the hood and throw the bypass switch on your jumper in an emergency.
 

Rhinebeck01

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Shame on me for not reading the other 27 pages in the thread first...
But would it not be ideal to run a battery disconnect switch in the jumper lead with the fuse? That would save the trouble of physically removing the cable connection or pulling the fuse which is not ideal either as a fuse holder has a limited number of times a fuse can be removed before losing its clamping force.
Currently I have a dying main battery but the aux is covering starting duties. The built in isolator is keeping my aux hot but I'd like to just pop the hood and throw the bypass switch on your jumper in an emergency.
@Toycrusher
https://www.jlwranglerforums.com/forum/threads/ess-dual-battery-management.60034/
 

Gee-pah

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Shame on me for not reading the other 27 pages in the thread first...
But would it not be ideal to run a battery disconnect switch in the jumper lead with the fuse? That would save the trouble of physically removing the cable connection or pulling the fuse which is not ideal either as a fuse holder has a limited number of times a fuse can be removed before losing its clamping force.
Currently I have a dying main battery but the aux is covering starting duties. The built in isolator is keeping my aux hot but I'd like to just pop the hood and throw the bypass switch on your jumper in an emergency.
Although Jerry's question to answer @Jebiruph, I imagine you could "kill two birds with one stone" here and go with one of these: a circuit breaker and manual on/off switch :)

https://www.amazon.com/Circuit-Brea...d=1&keywords=LENKRAD+30&qid=1611942641&sr=8-4
 

Toycrusher

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Toycrusher

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Hardest part of the bypass is finding the metric nuts!
20210129_173947.jpg
 

demisx

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In preparation to start from the main battery, I've followed the instructions in the OP post. However when I disconnected ground and Aux (+), I am still seeing 12V on the N1 post. Any idea what I'm missing?

Also, when I added N1->N2 jumper, my panel was still dead. 🤷‍♂️ After all, we do disconnect ground from the main battery here, don't we? I am not clear how this would work.

Thank you.

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WranglerMan

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I’m sure Jerry can jump in but from my understanding if you want to run the main one would just jumper N1 to N2 and disconnect the ESS negative off the main negative but to be honest I’m not sure as I don’t even run this system anymore, my ESS battery is gone.
 

demisx

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I’m sure Jerry can jump in but from my understanding if you want to run the main one would just jumper N1 to N2 and disconnect the ESS negative off the main negative but to be honest I’m not sure as I don’t even run this system anymore, my ESS battery is gone.
Yep, this what makes sense to me too. However, many earlier posts talk about and show disconnecting the ground wire from the main battery post. Maybe 2021 JLUR (manual) wiring is different, but when I do that neither of my batteries (-)s become connected to the ground and all panel instruments are dead. Perhaps, other models still have it grounded via some other wire, but not in my rig.

I've also noticed that my center ground post on the passenger side by the PDC box is empty whilst others show another wire connected to it. Please see attached pic.

IMG_2078.jpg
 

OldGuyNewJeep

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In preparation to start from the main battery, I've followed the instructions in the OP post. However when I disconnected ground and Aux (+), I am still seeing 12V on the N1 post. Any idea what I'm missing?

Also, when I added N1->N2 jumper, my panel was still dead. 🤷‍♂️ After all, we do disconnect ground from the main battery here, don't we? I am not clear how this would work.

Thank you.

IMG_2074.jpg


IMG_2076.jpg


IMG_2075.jpg
Why have you disconnected ground? Jump N1/N2 and disconnect AUX negative (preferably via a battery switch to make things tidy).
 

demisx

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Why have you disconnected ground? Jump N1/N2 and disconnect AUX negative (preferably via a battery switch to make things tidy).
Unless I am misunderstanding something or just overwhelmed from reading dozens of posts during the last couple of days, here is what I've derived from the OP's first post (see attached pic). I've disconnected the same wires in my 2021 JLUR 3.6L manual, but lost ground completely.

aux bat disconnected.jpg
 
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Jebiruph

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Unless I am misunderstanding something or just overwhelmed from reading dozens of posts during the last couple of days, here is what I've derived from the OP's first post (see attached pic). I've disconnected the same wires in my 2021 JLUR 3.6L manual, but lost ground completely.

aux bat disconnected.jpg
@demisx , the wiring has changed as first reported (that I've seen) by @mazeppa about his 2021 JTR here https://www.jlwranglerforums.com/forum/threads/ess-dual-battery-management.60034/post-1365304. The body ground and aux negative cable ends are swapped at the main battery negative terminal. I'll update and post one of my diagrams to show what that changes.

As far as the empty body ground post, it looks like they ran the battery ground cable to the post on the left in your pic. One less nut to install I guess.

1613837248283.png
 

demisx

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@demisx , the wiring has changed as first reported (that I've seen) by @mazeppa about his 2021 JTR here https://www.jlwranglerforums.com/forum/threads/ess-dual-battery-management.60034/post-1365304. The body ground and aux negative cable ends are swapped at the main battery negative terminal. I'll update and post one of my diagrams to show what that changes.

As far as the empty body ground post, it looks like they ran the battery ground cable to the post on the left in your pic. One less nut to install I guess.
Thank you so much! Those were my suspicions and you have confirmed them. Your posts are a life saver.
 

Gee-pah

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In preparation to start from the main battery, I've followed the instructions in the OP post. However when I disconnected ground and Aux (+), I am still seeing 12V on the N1 post. Any idea what I'm missing?

Also, when I added N1->N2 jumper, my panel was still dead. 🤷‍♂️ After all, we do disconnect ground from the main battery here, don't we? I am not clear how this would work.

Thank you.

IMG_2074.jpg


IMG_2076.jpg


IMG_2075.jpg
Hey Dee:

This is what, to use your words, I think you may be missing.

Your main battery is connected to N2, agreed? When the 3.6L JL is at rest, (in fact at all times but an instant at start and ESS events) N2 is connected to N1. I think this is what allows both batteries to be charged when they are connected as per factory, and charger cables are solely connected to the two terminals of the main battery when the vehicle is at rest.

So....at rest, N1 is energized from either or both batteries on the positive side--and in your case solely from the main battery because you've disconnected the ESS/Aux battery, and the other end of your tester is on the negative of the main battery. Stated yet another way, in your situation, N1 IS the positive of the main battery.

Provided your main battery has power, your meter should show voltage resistance.

I think this is the answer. I hope this helps. :)
 

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