3.6L ESS Aux Battery Bypass

MoparTH

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I've been running with no aux battery for about 1 1/2 years now, I would definitely recommend running something more than a 30 amp fuse and 10 gauge wire, I tried that and it let me down in about a week (melted the fuse holder also). I would suggest at minimum 8 gauge wire and at least 40A fuse, I went a different route and used the internal 150A fuse at N3 and used a short 6 gauge jumper. With just the radio at half volume and heater fan wide open is about 31 amps.

Aux Battery Current.jpg
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TroyBoy

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I've been running with no aux battery for about 1 1/2 years now, I would definitely recommend running something more than a 30 amp fuse and 10 gauge wire, I tried that and it let me down in about a week (melted the fuse holder also). I would suggest at minimum 8 gauge wire and at least 40A fuse, I went a different route and used the internal 150A fuse at N3 and used a short 6 gauge jumper. With just the radio at half volume and heater fan wide open is about 31 amps.
what if you turned your driving lights on too? I wonder if that would be over 40A? I like your idea of using the 150A fuse. Are you using the ESS still. If so I wonder if it causes that so called 7 cycle ESS error?
 

Rhinebeck01

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I've been running with no aux battery for about 1 1/2 years now, I would definitely recommend running something more than a 30 amp fuse and 10 gauge wire, I tried that and it let me down in about a week (melted the fuse holder also). I would suggest at minimum 8 gauge wire and at least 40A fuse, I went a different route and used the internal 150A fuse at N3 and used a short 6 gauge jumper. With just the radio at half volume and heater fan wide open is about 31 amps.
@MoparTH

I gather you have removed the Aux altogether.... ?

I started running with the Aux bypassed (Aux is still in it's housing, maintained with battery maintainer/tender) .... running with just the Main battery, just over 2 years ago., and have driven just over 29,000 with just the Main in play so to speak.. I have kept/keep, the Aux as a b/u start battery should I need it.

At first, I used, a fused N1-N2 fused bypass jumper.... at that time that one, was 10g and had a 30 amp fuse..

After say 6 months of running with the 30 amp fuse, and absolutely, no problems, I read on the forum, someone (maybe you) saying that 31+ a tad, could come into play so best to move to a 40 amp fuse.. which I did.. Never any problems doing that.... running with 10g and 40 amp.

Over the last 3+ months and about 4,000 mi., I have been running an N1-Main Pos., 10g wire jumper with a 40 amp fuse. Again, never any issues.. fuse holder shows no sign of heat damage...

By the way, I have a 3.6, Rubi.... the last few months, I have been running the heater fan at medium/high, window defrosters, usually both front seats heaters on, the radio going, etc. and never any issues with the 10g wire and 40 amp fuse..


@Jebiruph
 

MoparTH

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I still use ESS occasionally, it functions but the only difference I see is that it usually says "battery charging" for the first few minutes if driving if you look at the ESS screen.

what if you turned your driving lights on too? I wonder if that would be over 40A? I like your idea of using the 150A fuse. Are you using the ESS still. If so I wonder if it causes that so called 7 cycle ESS error?
 

Toycrusher

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I will say that I have new respect for the aux battery. I was having voltage issues and I thought my aux was on its way out. I did the bypass but still had issues. Interestingly, both my main and aux battery failed load test, but my main battery was definitely very shot. I was able to keep going over a month on just the aux battery. It finally got too weak and I had to bite the bullet and buy a new main, but I'm impressed how much I was able to squeeze from the 3 year old aux
 

JJT-NC

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I am running a 2020 JLRU 3.0; crapped out both batteries after flat towing 1,200 miles behind my RV. Was ACC on? Was the battery activated due to the supplemental braking system or other software gremlins? I don't want to find out - I would rather have a simple battery disconnect that kills both batteries.

I know this may be off topic here, but the level of knowledge on these systems is higher here than I have seen anywhere!

Since these batteries are connected in parallel (great diagrams Jerry!), would a top post disconnect switch like this cut all power (for towing and storage)? Thanks!
 
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Jebiruph

Jebiruph

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I am running a 2020 JLRU 3.0; crapped out both batteries after flat towing 1,200 miles behind my RV. Was ACC on? Was the battery activated due to the supplemental braking system or other software gremlins? I don't want to find out - I would rather have a simple battery disconnect that kills both batteries.

I know this may be off topic here, but the level of knowledge on these systems is higher here than I have seen anywhere!

Since these batteries are connected in parallel (great diagrams Jerry!), would a top post disconnect switch like this cut all power (for towing and storage)? Thanks!
Since the battery sensor is what connects to the battery top post, I'm not sure how you could make that work. Here's a picture that shows which body ground cable will disconnect both batteries.

battery no ground.jpg
 

NCIC105

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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.

Here's a picture of my bypass kit. The jumper is used to connect the N1 terminal to the N2 terminal. I wanted to be able to install the jumper securely, but still be able to quickly disconnect it. A fused jumper seemed to be the best and cheapest way to go. Removing the fuse is a simple way to disconnect the jumper and it protects against overloading the wire. I don't know how much current will pass through the wire, so I used the largest I could find.
bypass kit 2.jpg


Here's how I tested the bypass. I disconnected the Aux battery at N1 and the ground wire at the Main battery negative terminal to simulate a bad aux battery. The voltmeter confirms the disconnect with low voltage at N1.
aux bat disconnected.jpg


Here's a shot of the dead instrument panel due to the disconnected Aux battery.
dash off.jpg


Here's the jumper installed between N1 and N2, voltmeter shows the Main battery voltage at N1.
bypass installed.jpg


Here's the live instrument panel.
dash on.jpg


Here's the instrument panel after starting, only error indicated is open hood.
dash running.jpg



For those interested, following are some diagrams to illustrate how I understand it works. (See this thread for additional information on the dual battery system https://www.jlwranglerforums.com/forum/threads/3-6l-ess-battery-diagram.14401/)

Here's the battery voltages on a working system, the PCR is connecting the batteries in parallel, both batteries providing power to everything. Normal operation is verified with 0 volts between N1 and N2.
ess normal operation.PNG


Here's the effect of a failed Aux battery, no power to critical electronics. This should be verifiable by a voltage difference between N1 and N2.
ess bad aux.PNG


Bypassing is accomplished by jumping N1 to N2. This diagram illustrates the jumper getting power back to the critical electronics.
ess bypass.PNG



(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/
Great job and very detailed graphics. Thank you
 

Rubi

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I've been running with no aux battery for about 1 1/2 years now, I would definitely recommend running something more than a 30 amp fuse and 10 gauge wire, I tried that and it let me down in about a week (melted the fuse holder also). I would suggest at minimum 8 gauge wire and at least 40A fuse, I went a different route and used the internal 150A fuse at N3 and used a short 6 gauge jumper. With just the radio at half volume and heater fan wide open is about 31 amps.

Aux Battery Current.jpg

Just spoke with my local dealer concerning the removal of the aux battery and any warranty issues. They had a Rubicon come in that lost the front diff locking capability with a removed aux battery. They had to put the battery back in to get it to function properly. Have you had any problems along these lines. Anybody else reading this please chime in if you’ve removed your aux battery completely and experienced or didn’t experience the above problem.
 

OldGuyNewJeep

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Just spoke with my local dealer concerning the removal of the aux battery and any warranty issues. They had a Rubicon come in that lost the front diff locking capability with a removed aux battery. They had to put the battery back in to get it to function properly. Have you had any problems along these lines. Anybody else reading this please chime in if you’ve removed your aux battery completely and experienced or didn’t experience the above problem.
Yeah… that’s a steaming load of BS.
 

Rubi

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Yeah… that’s a steaming load of BS.
I was leaning that direction as well. Many people on this forum have did some aux battery system mod or removal with no complaint of any other malfunction.
 

Rock Hopper

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There are many of us that are operating with a disabled ESS (on purpose) and have no need for the aux battery. Is it safe to say that it (the small aux battery) can simply be removed or stay in place as dead weight without any long term consequences? For someone like myself that will NEVER use the ESS system, is the small aux battery even necessary? Under normal circumstances I would just pull the small aux battery, but it isn't that easy to get to without ripping open a pathway...again I am just going off of what I have read on these forums and have not yet had a need to go there. At some point it will be inevitable.

I think there is so much information floating around that those of us that are not great with electrical components remain a little confused.

If I continue to use my Jeep with the ESS disabled and eventually when my main battery gives up its starting capability, can I just replace the main battery and disregard any condition that the aux battery is in, OR is there a better way to approach the situation?

I have received some great information here, but it is still not completely clear what the best option is. I know others are equally confused.

Thanks in advance for any additional insight.
 

WranglerMan

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@Rock Hopper it is my understanding that yes you can bypass the aux battery using @Jebiruph jumper or similar but if the aux battery gives up the ghost and say shorts out and it’s still in the circuit it can pull the main battery down and by just replacing the main with a new one if the aux is still bad it will pull power from the new one to equalize and eventually suck the life from the main crank battery so it’s best to disconnect it altogether if you will never use ESS and there are a host of ways to do this.

Some pull the PDC and go in from the top and others remove the fender and go that route so if you are wanting to just get rid of the battery I would suggest removing it and then move the ESS positive to the main crank battery and then disconnect the ESS negative and be done and it would not be a bad idea to step up to a better battery like Northstar or similar

Mine has be gone for many months but I run a different system compared to stock and don’t use jumpers.
 

Rufus

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Any new upgraded aftermarket options for the aux battery?
 

moodywizard

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Just spoke with my local dealer concerning the removal of the aux battery and any warranty issues. They had a Rubicon come in that lost the front diff locking capability with a removed aux battery. They had to put the battery back in to get it to function properly. Have you had any problems along these lines. Anybody else reading this please chime in if you’ve removed your aux battery completely and experienced or didn’t experience the above problem.
No issue running my genesis setup for 1.5 years with the IBS sensor removed for full time 14V+ charging. I dont trust anything or any word that comes from someone working at a dealer. Sorry for those that are offended.
 
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