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3.6L ESS Dual Battery Consolidated Information

timn1984

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Aux Battery Bypass (PCR Bypass)
(updated 03/24/2019)

To accommodate the dual battery ESS system, the JL electronics have been separated into Aux powered systems and Main powered systems. The PCR (power control relay) is used to connect and disconnect the systems as needed. A bad or discharged aux battery can affect the operation of the PCR, disrupting both the operation of the electronics and the starting procedure.

Using a jumper to bypass the PCR or unplugging it may restore the ability to start. The jumper is installed between PDC terminals N1 (aux systems) and N2 (main systems) and directly connects the two systems, effectively bypassing the PCR. Unplugging the PCR (disabling it) keeps the main and aux systems always connected, but this will not work with a bad PCR or a blown PCR fuse.
ess bypass simple 4.PNG



Here's what using a jumper looks like, and it's discussed in this htread.
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-aux-battery-bypass.17293/

bypass installed.jpg



The PCR is located behind the front passenger side tire, and it is discussed in the thread. (See posts 75, 92, 93)
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-battery-diagram.14401/

View attachment 158893


Reading Individual Battery Voltage
(updated 04/13/2019)

Since the batteries are usually connected in parallel, following is how to electrically isolated them to check the individual battery voltage. Keep in mind that the best way to check the condition of a battery is load testing it, which is covered in this thread.
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-battery-basic-load-testing.22031/

There are two cables connected to the Main battery negative terminal, one is from the Aux battery negative terminal and the other is to the body ground. Disconnecting the Aux battery negative cable from the Main battery negative terminal will isolate the batteries to facilitate reading the voltage of the individual batteries.

Here's reading the aux battery voltage - Main positive terminal to Aux battery ground.
aux bat gnd.jpg



Here's reading the main battery voltage - Main positive terminal to Main battery ground.

main bat gnd.jpg
You are a good man. You need to find a Day Job! Thanks for the research..... Job well done.
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Jebiruph

Jebiruph

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Why can’t you just take positive terminal off ess battery connect to top battery and just run with top battery eliminating ess bat instead of buying that dual bat kit from genisis I don’t use start stop so sounds simple I’m sure it is not but you seem way more knowledgeable to answer my question if you no answer
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-aux-battery-bypass.17293/page-7 post #97 has a diagram of what that looks like. It is that simple, my only concern would be warranty issues when the Aux battery fails with the non factory cabling. Using the jumper lets you leave the factory cables in place and it's easily removed if needed.
 
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Jebiruph

Jebiruph

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You are a good man. You need to find a Day Job! Thanks for the research..... Job well done.
Yea, I'm not making much money at this. I lose money (time/resources) on each post, but I'm hoping to make it up in volume.
 

Stormin’ Moorman

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This post is amazing, thanks to everyone who contributed. But I'm dumb and going to need a YouTube video on how to jumpstart my jeep. Haha
 

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Jerseyed1975

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With my previous non-Jeep vehicle, I used to gladly help others jump start their dead batteries, until one day, it would kill my battery days later and a battery test determined it needed to be replaced. Same thing happened 3 times over the years so I no longer jump start other vehicles, unless it is a desperate situation. I'm not sure if all 3 batteries were on their last leg aka bad timing 3 times in a row, a barely producing alternator or what. Is there any fear of this happening to a JL when assisting to jump other vehicles that need help? Will jumping other vehicle's dead batteries degrade the life of the JL batteries?
Jeep a jumper pack in the jeep incase someone needs a jump. Can pickup a serviceable one for around $50
 

Shakey Graves

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Is there a way ESS could be working and the jeep starting, yet not powering the radio/accessories? I'm wondering because my radio is not working, but it is lighting up the knobs and buttons (every couple secs), but not turning the screen on. I know the radio is a piece of junk and probably broken, but wanted to see if the accessory battery was the culprit as opposed to the actual uconnect unit.
 
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Jebiruph

Jebiruph

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Is there a way ESS could be working and the jeep starting, yet not powering the radio/accessories? I'm wondering because my radio is not working, but it is lighting up the knobs and buttons (every couple secs), but not turning the screen on. I know the radio is a piece of junk and probably broken, but wanted to see if the accessory battery was the culprit as opposed to the actual uconnect unit.
If everything else is working, it's a bad radio.
 

Martindfletcher

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This was great information.

Does anyone know what causes the ess to be disabled due to “battery protection” not to be confused by low battery? Mine does this every long road trip.
 
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Jebiruph

Jebiruph

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This was great information.

Does anyone know what causes the ess to be disabled due to “battery protection” not to be confused by low battery? Mine does this every long road trip.
The owners manual explains Battery Saver Mode (p.185), I think it's the same thing. Some optional electrical functions are disable to avoid draining the battery. You should have the dealer check the electrical system.
 

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Martindfletcher

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The owners manual explains Battery Saver Mode (p.185), I think it's the same thing. Some optional electrical functions are disable to avoid draining the battery. You should have the dealer check the electrical system.
I’m trying to avoid the dealer for an issue that takes several hours to reproduce.

I will load test the ess battery and see what I get.
 
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Jebiruph

Jebiruph

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I’m trying to avoid the dealer for an issue that takes several hours to reproduce.

I will load test the ess battery and see what I get.
Check both batteries and if they are good, try disconnecting the IBS to reset it. It's the IBS that puts it in battery saver mode.
 
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Jebiruph

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I have some accessories grounded there as well could that contribute?
Read the owners manual and see what you think. This is one time when the owners manual has a good explanation.
 

Martindfletcher

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Read the owners manual and see what you think. This is one time when the owners manual has a good explanation.

I read it already. The description does not jive with my symptoms, mine goes into battery protection mode when fully charged on long road trips, the voltage drops to 12.7/9 when accelerating and charges up 13.5/14V when i coast, none of the accessories like heated seats are being turned off, maybe there is more if I read past some of the other errors,
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