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3.6L ESS Aux Battery Bypass

SolarWizard

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I was intending to integrate a solar charge controller that accepts DC from an alternator as a solar and then run one of our 375w panels on my carge rack. That way the bed battery should get A big boost from solar during the day. Don’t want to carry propane or generator
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Petey

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Sorry i am completely new at this kind of electrical knowledge, but somehow i feel that this thread is super important for what i intend to do with my JL. If i am at my shack in the cliffs (no service whatsoever possible), and the aux battery depletes...what can i do? I am concerned that i would be left stranded over there. Back then we could simply bring an extra main battery, but in this case...should i bring an extra "aux" battery?
From what I see in the diagram above, u would just need just one battery and some extra wire (appropriate gauge size) cable with quality terminals to make a jumper harness and make it into a single battery system.
 

RubiRob

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This image is from
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-aux-battery-bypass.17293/
I don't recall the wire guage I used. I went to Autozone and bought a fused jumper off the rack rated for 30 amp fuse and just added the ends to fit the fuse box n1-n2 terminals.

fused jumper.jpg
would this work?
10ga Fuse Holder, 2 Pack MUYI Inline Fuse Holder 10 Gauge Fuse holders 12v Waterproof Pigtail Blade Fuse Relay with 40AMP ATC Fuses https://www.amazon.com/dp/B07G7YMJXW/ref=cm_sw_r_cp_api_glc_fabc_2oz1Fb3XAQTXQ
 
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Jebiruph

Jebiruph

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would this work?
10ga Fuse Holder, 2 Pack MUYI Inline Fuse Holder 10 Gauge Fuse holders 12v Waterproof Pigtail Blade Fuse Relay with 40AMP ATC Fuses https://www.amazon.com/dp/B07G7YMJXW/ref=cm_sw_r_cp_api_glc_fabc_2oz1Fb3XAQTXQ
Thicker wire is always better electrically, but thicker wire starts interfering with the PDC cover. I used a 10 ga wire here https://www.jlwranglerforums.com/forum/threads/ess-dual-battery-management.60034/post-1296147 , but instead of connecting it to N1 and N2, I went from N1 to the main battery positive terminal which is electrically the same as N1 to N2, but interferes with the PDC cover less.
 

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OldGuyNewJeep

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I've seen quite a few posts related to failed Aux batteries causing flaky or dead electronics, stalling and failing to start/auto restart. I've come up with a simple way to temporarily bypass a bad Aux battery (also blown PCR fuse or bad PCR) and get back on the road. Warning - this post contains a lot of informed assumptions, so post your related experiences to help validate or invalidate any information I've provided.

(updated 04/13/2019)
Additional 3.6L ESS system information is available here.
3.6L ESS Dual Battery Consolidated Information
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-dual-battery-consolidated-information.25377/
@Jebiruph, this is such great info. I have a couple of questions that I didn’t see asked or answered in the various threads:
  • What happens if you’re driving along and the fuse blows? Anything?
  • With fused jumper in place, I still see continuity between the disconnected AUX negative and the main battery positive. Looking at all of your various drawings, I believe this is expected. Can you confirm?
  • What is the effect, if any, of connecting the AUX negative with the fused jumper in place. For example, if using a battery switch and I want to trickle charge the AUX, is there any harm leaving the fuse in place?
  • Is 30a still the recommendation? Or has that been superseded by 40a?
Also, FYI that wing nuts have to be filed or they’ll touch and short. At least the M6 ones that I had on hand needed to be filed. I decide to use regular tension nuts, instead.
 
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WranglerMan

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I don''t know why you couldn't set up a dual full size battery system like Genesis with one of the batteries in the bed. I'm not a dual battery system expert, but @SpookyXJ posted a setup that used an ignition triggered relay to activate a battery isolater only when the jeep is running. You'll still have to figure out how you want to disable ESS
Jerry,

I would think if one had a mind to they could pull out the ESS battery then get the Genesis tray without the top and run two full size batteries, you would have to modify the cabling some and then you would have one battery dedicated for the crank battery then one full size battery for ESS, I chose the Genesis system with the control relay on top and at first I had lots of concerns on the Cole Hersee relay pulling down the main crank when it’s parked but over the time I have had it so far it works perfectly and provides me with the additional power for my winch and compressor and also a sort of built in jump pack,.

There are less expensive options than the Genesis but one has to realize that running a dual battery system regardless of whether it’s Genesis or not the cost of the higher quality AGM’s like Odyssey or Full River are 1/2 the cost of the investment in most cases, and if one did run there own dual setup you can shop around for budget minded batteries but we all know batteries don’t last forever.
 

RubiRob

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So is there anyway I can remove my aux so they can test it at orielly (it’s a 2 month old replacement I got from them and they said they test takes 1/2-1hr) and drive with just only my main?

Jeep Wrangler JL 3.6L ESS Aux Battery Bypass 2D0860B3-7A05-4CA9-A720-D011BBFC54B4
 

Leisure Freak

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would this work?
10ga Fuse Holder, 2 Pack MUYI Inline Fuse Holder 10 Gauge Fuse holders 12v Waterproof Pigtail Blade Fuse Relay with 40AMP ATC Fuses https://www.amazon.com/dp/B07G7YMJXW/ref=cm_sw_r_cp_api_glc_fabc_2oz1Fb3XAQTXQ
It looks like it should work based on what I have been reading but listen to Jebiruph because I made mine for emergency use at this time to carry and have ready and have not tested it yet. Eventually once warranties are up I intend to go this route or get something like the genesis system as WranglerMan has done.
.
 

OldGuyNewJeep

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So is there anyway I can remove my aux so they can test it at orielly (it’s a 2 month old replacement I got from them and they said they test takes 1/2-1hr) and drive with just only my main?

Jeep Wrangler JL 3.6L ESS Aux Battery Bypass 2D0860B3-7A05-4CA9-A720-D011BBFC54B4
Yes, but it will take you much longer to remove it and put it back in than an hour. Just have them test it with it in the vehicle. If you’re still under warranty, make the dealer do it. I just got a new AUX battery installed under warranty on Friday.
 

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Gee-pah

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I have read the same, not needed to start/run for the late 2018+ models but I read that the jumper will bypass seeing any ESS error messages since the jumper provides 12v to n1 terminal where the system looks for the aux battery. That's at least my understanding, I haven't tested it but other forum members have.
Here's the skinny on this situation Tommy.

A 3.6L JL with Jerry's jumper will always start on the first crank, regardless of the state of the ESS/Aux battery, provided the main battery has ample power.

To the 3.6L with Jerry's jumper calls the vehicle makes to, and thinks are to the ESS/Aux battery are rerouted to the main.

Without this jumper and a 2018 without the flash, a dead ESS/Aux battery will leave you stranded.

2018's with this flash, or later model years who fail on the first crank of the ESS/Aux battery lacks sufficient power, and on subsequent attempts to cold crank, attempt to crank off the main battery.

If successful, ESS is disabled and indicated on the display, and not allowed to operate again (turning the diagnostic no ESS light off automatically) until the next, if any, cold crank where the vehicle's ESS/Aux battery has been charged, replaced and charged, or bypassed with wiring to the main battery with power, such that the vehicle detects power in (what may be what it things is--if bypassed) the ESS/Aux battery.
 

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I was intending to integrate a solar charge controller that accepts DC from an alternator as a solar and then run one of our 375w panels on my carge rack. That way the bed battery should get A big boost from solar during the day. Don’t want to carry propane or generator
From your namesake, I suspect you've forgotten more solar things than I know.

But it sounds like you seek to charge your own self contained battery from a solar panel...a battery that resides in the cab?

Would you agree that a more stable and less prone to voltage changes with temperature Lithium Iron (not Ion) Phospate (i.e. LiFePO4) battery might be best here---assuming I've understand your desired setup?
 

RubiRob

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Yes, but it will take you much longer to remove it and put it back in than an hour. Just have them test it with it in the vehicle. If you’re still under warranty, make the dealer do it. I just got a new AUX battery installed under warranty on Friday.
It’s not bad I had it out in 20 minutes. So it will run fine without the aux them to be sure? I have an early 18 and never had any updates to the computer.
 

OldGuyNewJeep

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It’s not bad I had it out in 20 minutes. So it will run fine without the aux them to be sure? I have an early 18 and never had any updates to the computer.
It will only run with it out if you install the jumper. Might be more to it than that, too - best to wait for Jerry’s reply.
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