Sponsored

3.6L ESS Aux Battery Bypass

Rhinebeck01

Well-Known Member
Joined
May 9, 2018
Threads
155
Messages
11,869
Reaction score
17,109
Location
Multiple places..
Vehicle(s)
'18 JL Rubi, '22 Prevost M H3-45,'01 Harley FatBoy

OldBlue

Well-Known Member
First Name
Doug
Joined
Dec 2, 2021
Threads
19
Messages
939
Reaction score
1,646
Location
Chatham Twp, OH
Vehicle(s)
See my Signature
Build Thread
Link
Occupation
Aerospace Forgings Test Lab
Vehicle Showcase
3
Lots of great info here from a LOT of very smart people. I read through the first few pages and last 6 or so, and I have to admit my eyes started to gloss over, as I tried to follow all the info but got lost. 😳 Wondering if anyone tried this bypass with the 2.0L? Both my Jeeps ('20 JLU and '19 WK2) use the auxiliary battery and I'd love to bypass it in both of them. I still need to do more research on the WK2 forum to see if it's possible on that one.
 

StaindReality

Well-Known Member
First Name
David
Joined
Aug 11, 2018
Threads
20
Messages
116
Reaction score
44
Location
Kansasncity
Vehicle(s)
Ram 1500 crew cab black out
You only need the jumper if you don't have the software update and can't start without it. If you have the software update, the jumper just keeps the ESS test from failing and turning on the error light. I wouldn't bother taping up the cable either, just bend it out of the way.
So to verify. I have a 19 sport. I do not need the jumper? I just have to disconnect the negative aux from the main battery to stop using the aux battery all together when I replace my main battery?
 

Sponsored

Rhinebeck01

Well-Known Member
Joined
May 9, 2018
Threads
155
Messages
11,869
Reaction score
17,109
Location
Multiple places..
Vehicle(s)
'18 JL Rubi, '22 Prevost M H3-45,'01 Harley FatBoy
Will tazer take warning light off?
@StaindReality

So, you would have no issue with..... with the EVIC light coming on .... being there all the time on your 2019 JL ? You would see the JL start on the second try .. have the error light.

You will want the jumper!!

Just easily install the $8.00+- fused, N1-N2 bypass jumper and you will have none of that. JL will start on first attempt and no error light thrown/turned on. Yes, you also have to have the Aux negative wire disconnected from the Main battery Neg. terminal.

.
 

jeepdabest

Well-Known Member
First Name
Bobby
Joined
Mar 27, 2019
Threads
20
Messages
980
Reaction score
1,548
Location
Arizona
Vehicle(s)
2019 JL Sahara
So to verify. I have a 19 sport. I do not need the jumper? I just have to disconnect the negative aux from the main battery to stop using the aux battery all together when I replace my main battery?
Without jumper you will have a yellow warning light on dash
 

StaindReality

Well-Known Member
First Name
David
Joined
Aug 11, 2018
Threads
20
Messages
116
Reaction score
44
Location
Kansasncity
Vehicle(s)
Ram 1500 crew cab black out
Ok. Thank you for quick response. I got 10 ga. 40 amp inline fuse coming. I’ll go ahead and replace old main battery with new battery now and use the jumper Thursday when jumper arrives

One more question. When hooking up the jumper. Is it required to unhook main battery at all? Or just hook up jumper. Then unhook aux. negative.
 

Rhinebeck01

Well-Known Member
Joined
May 9, 2018
Threads
155
Messages
11,869
Reaction score
17,109
Location
Multiple places..
Vehicle(s)
'18 JL Rubi, '22 Prevost M H3-45,'01 Harley FatBoy
Ok. Thank you for quick response. I got 10 ga. 40 amp inline fuse coming. I’ll go ahead and replace old main battery with new battery now and use the jumper Thursday when jumper arrives

One more question. When hooking up the jumper. Is it required to unhook main battery at all? Or just hook up jumper. Then unhook aux. negative.
@StaindReality

You'll need Wing Nuts (see pic for size) to secure the N1-N2 fused bypass jumper.

No need to "unhook Main battery".

Do not use/ loosen the nuts that are securing N1 and N2. Place one ring connector on N1 and secure with a Wing nut. Do the same with the other ring connector and a wing nut in regard to N2.

Just have the 40 amp fuse out of the fused bypass fuse holder ..... and secure the 2 ring connectors and then insert the 40 amp fuse.

Remember to disconnect the Aux Neg. wire that is connected on the Neg terminal of the Main battery.

Do all mentioned and you will be set-up to run with just the Main battery.

Remember, when running with just the Main battery ....to not use of limit use of ESS. Press the ESS button or buy and adjunct that does that for you .... like a SmartStopStart unit.


Jeep Wrangler JL 3.6L ESS Aux Battery Bypass jumper
 

Sponsored

Rhinebeck01

Well-Known Member
Joined
May 9, 2018
Threads
155
Messages
11,869
Reaction score
17,109
Location
Multiple places..
Vehicle(s)
'18 JL Rubi, '22 Prevost M H3-45,'01 Harley FatBoy
@StaindReality

You will be disconnecting #6 in the picture below. That is the Aux battery Negative on the Main battery Neg terminal..

Disconnect it and cover the end with something non-conductive.

Leave a Wing Nut on the terminal that you took the nut off to disconnect the cable.

This way if you want to reconnect for any reason, you can do with no tools, thanks to the Wing nut.

Jeep Wrangler JL 3.6L ESS Aux Battery Bypass battery numbered
 

StaindReality

Well-Known Member
First Name
David
Joined
Aug 11, 2018
Threads
20
Messages
116
Reaction score
44
Location
Kansasncity
Vehicle(s)
Ram 1500 crew cab black out
You all are great. Thank you so much for quick response and helping get this straight.
 

Rhinebeck01

Well-Known Member
Joined
May 9, 2018
Threads
155
Messages
11,869
Reaction score
17,109
Location
Multiple places..
Vehicle(s)
'18 JL Rubi, '22 Prevost M H3-45,'01 Harley FatBoy

Paulguy100

Well-Known Member
Joined
Nov 3, 2020
Threads
87
Messages
202
Reaction score
94
Location
Wisconsin
Vehicle(s)
2021 JLU Rubicon
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.

6/26/2021 Update - Many have reported that the 30A fused jumper shown in this picture has not been adequate for their JL. Use the highest capacity fused jumper you can find and make sure the fuse is not rated too high for the wire, otherwise the wire will melt before the fuse blows.
Jeep Wrangler JL 3.6L ESS Aux Battery Bypass battery numbered


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.
Jeep Wrangler JL 3.6L ESS Aux Battery Bypass battery numbered


Here's a shot of the dead instrument panel due to the disconnected Aux battery.
Jeep Wrangler JL 3.6L ESS Aux Battery Bypass battery numbered


Here's the jumper installed between N1 and N2, voltmeter shows the Main battery voltage at N1.
Jeep Wrangler JL 3.6L ESS Aux Battery Bypass battery numbered


Here's the live instrument panel.
Jeep Wrangler JL 3.6L ESS Aux Battery Bypass battery numbered


Here's the instrument panel after starting, only error indicated is open hood.
Jeep Wrangler JL 3.6L ESS Aux Battery Bypass battery numbered



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.
Jeep Wrangler JL 3.6L ESS Aux Battery Bypass battery numbered


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.
Jeep Wrangler JL 3.6L ESS Aux Battery Bypass battery numbered


Bypassing is accomplished by jumping N1 to N2. This diagram illustrates the jumper getting power back to the critical electronics.
Jeep Wrangler JL 3.6L ESS Aux Battery Bypass battery numbered



(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/
Will this work for the diesel as well?
 

BRuby

Well-Known Member
Joined
Nov 28, 2019
Threads
5
Messages
535
Reaction score
607
Location
Backcountry Mtns
Vehicle(s)
JLUR-A Benz-A Porsche-M Subie-M
@StaindReality

You will be disconnecting #6 in the picture below. That is the Aux battery Negative on the Main battery Neg terminal..

Disconnect it and cover the end with something non-conductive.

Leave a Wing Nut on the terminal that you took the nut off to disconnect the cable.

This way if you want to reconnect for any reason, you can do with no tools, thanks to the Wing nut.

battery numbered.jpg
Once the aux cable is disconnected you should keep it smart charged on a regular basis to maintain and prolong its battery health. Since the alternator will no longer charge the aux once disconnected. The main will be the only battery in operation getting charged by the alternator.

We operated with the aux disconnected and the ESS trouble icon stayed lit on our dash while driving. This was expected as ESS was completely disabled. However once the aux was reconnected the dash light stayed lit for our JL. To remove the ESS trouble icon we simply disconnected the main neg lead for about a minute. Once both batteries were reconnected the dash ESS trouble icon was gone.

We hook up both batteries from time to time to ensure the ESS works as OEM designed. Typically stored outside at freezing temps the dash shows ESS is available to use after about a minute of driving. Our 2018 starts on the second ignition press when the aux is disconnected. Thereafter starts on the first press on main alone.

Here is a photo of our NOCO quick disconnect setup allowing both separate battery smart charging and separate battery smart desulfate reconditioning. The aux neg lead is the one attached to the black alligator clip. We use a NOCO 5 for the aux and a NOCO 7200 for the main. Both batteries are still OEM from 2018 and have been load tested by the dealer.

QUOTE="Jebiruph, post: 1760874, member: 14234"]
If you don't care if the error light is on, all you have to do is disconnect the aux ground cable. I was doing some ESS testing today and did this myself for a multi stop trip. The first start attempt will fail, every start after that will work as long as nothing else is wrong. Then shortly after starting the error light turns on.
[/QUOTE]
100%

https://www.jlwranglerforums.com/fo...battery-consolidated-information.25377/page-6

Jeep Wrangler JL 3.6L ESS Aux Battery Bypass 0F2A6B16-B493-403F-9FBD-5A18F1016247
Sponsored

 
Last edited:
 



Top