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3.6L ESS Dual Battery Consolidated Information

Kenc

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Is there any idea what the life expectancy is for the auxiliary battery? I would just like to be proactive and replace it at a certain interval rather than waiting for it to die.
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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?
 
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Here are a couple diagrams of the starting system relays. They show how the relays are connected to each other and to the BCM and PCM. Based on various inputs, the BCM and PCM control the starter and the PCR through the related relays. For the second diagram, I added green (AUX) and blue (Main) dashed lines to show how the different batteries interact with the relays.

The diagrams show the IBS (Intelligent Battery Sensor) is connected to the BCM. The BCM also controls the Stop/Start Relay, which in turn affects the operation of the Starter Solenoid Relay and the PCR Control Relay. So based on the information from the IBS, the BCM can control whether or not ESS can activate.

starting relays 1.PNG

starting relays 2.PNG
 
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bbradshaw14

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Is there any idea what the life expectancy is for the auxiliary battery? I would just like to be proactive and replace it at a certain interval rather than waiting for it to die.
My JLU Sahara was bought 12 months ago. About 5 months ago, my ESS stopped working. No error message only stated that ESS was not ready due to battery charging. I had a busy winter with my son's travel hockey schedule so only last Saturday got it in for service. Both the main and aux battery failed load testing and had to be replaced. Seems pretty weird to me at 12,200 miles to have both replaced when a traditional system they would last 5 years or so??? They checked the electrical system but found nothing wrong. If this happens again then apparently they are wrong. Time will tell.
 

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Jebiruph

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. . . As I see it, your jumpering changes the 3.6L JL from having the batteries in parallel 99.9% of the time (baring pre-cranks and ESS events) to 100% of the time. And I believe you may share my belief in suggesting people disable ESS if using your jumpering. . . .
I don't have time to respond to everything in your post, it will be better if you pick one thing at a time to discuss. As to disabling ESS when you run on one battery, I don't think it's necessary since the Cherokee runs ESS with just one battery. Although I don't think running the JL with one battery makes it the same as the Cherokee, I expect the Cherokee system more efficiently uses the single battery.
 
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Jebiruph

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My JLU Sahara was bought 12 months ago. About 5 months ago, my ESS stopped working. No error message only stated that ESS was not ready due to battery charging. I had a busy winter with my son's travel hockey schedule so only last Saturday got it in for service. Both the main and aux battery failed load testing and had to be replaced. Seems pretty weird to me at 12,200 miles to have both replaced when a traditional system they would last 5 years or so??? They checked the electrical system but found nothing wrong. If this happens again then apparently they are wrong. Time will tell.
Running two batteries in parallel with no battery management can cause problems, especially if one goes bad. The good battery can run down trying to charge the bad battery and in the process go bad itself. If it happens again, it's still probably bad batteries.
 

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I don't have time to respond to everything in your post, it will be better if you pick one thing at a time to discuss. As to disabling ESS when you run on one battery, I don't think it's necessary since the Cherokee runs ESS with just one battery. Although I don't think running the JL with one battery makes it the same as the Cherokee, I expect the Cherokee system more efficiently uses the single battery.
I hear this Jerry. My thoughts: the threshold for not entering into an ESS event on the 3.6L JL, or once in it, getting out before the operator takes their foot off the brake may be different (less) that for the Cherokee--as the ESS battery only needs power to merely signal the starter via the starter relay: a current amount less than actually spinning a starter I imagine.

Energizing that starter in something that thee Cherokee's one battery you describe does in isolation, and that the 3.6L JL has both batteries to depend upon for (I believe.)

I admit to not knowing where FCA sets that threshold for the ESS battery and if it is less stringent than the one on the one battery Cherokee you describe, as this latter case needs to leave enough juice in the only battery to also turn the starter.

: - )

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If all I had is a portable battery jump starter, is there a way to get the Jeep started if both batteries were drained?
 

Kenc

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My JLU Sahara was bought 12 months ago. About 5 months ago, my ESS stopped working. No error message only stated that ESS was not ready due to battery charging. I had a busy winter with my son's travel hockey schedule so only last Saturday got it in for service. Both the main and aux battery failed load testing and had to be replaced. Seems pretty weird to me at 12,200 miles to have both replaced when a traditional system they would last 5 years or so??? They checked the electrical system but found nothing wrong. If this happens again then apparently they are wrong. Time will tell.
Were you actively using the ESS system or would you leave it turned off?
 

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I hear this Jerry. My thoughts: the threshold for not entering into an ESS event on the 3.6L JL, or once in it, getting out before the operator takes their foot off the brake may be different (less) that for the Cherokee--as the ESS battery only needs power to merely signal the starter via the starter relay: a current amount less than actually spinning a starter I imagine.

Energizing that starter in something that thee Cherokee's one battery you describe does in isolation, and that the 3.6L JL has both batteries to depend upon for (I believe.)

I admit to not knowing where FCA sets that threshold for the ESS battery and if it is less stringent than the one on the one battery Cherokee you describe, as this latter case needs to leave enough juice in the only battery to also turn the starter.

: - )

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The ESS battery doesn't signal the starter, the BCM and PCM do all the signaling through the various relays. And relay operation depends on both batteries, one powers the coil while the other battery is switched. (see the previously posted relay diagram).

I do agree that it's possible the single battery Cherokee system may have different thresholds that the dual battery Wrangler system, but not necessarily.
 
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Jebiruph

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If all I had is a portable battery jump starter, is there a way to get the Jeep started if both batteries were drained?
If you know that the Aux battery is a good battery that's just drained, I think your best bet is to disconnect the Main battery ground and use the booster on just the Aux battery. That way the booster is not splitting it's charge between both batteries.

charging aux.jpg
 

Rahneld

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The ESS battery doesn't signal the starter, the BCM and PCM do all the signaling through the various relays. And relay operation depends on both batteries, one powers the coil while the other battery is switched. (see the previously posted relay diagram).

I do agree that it's possible the single battery Cherokee system may have different thresholds that the dual battery Wrangler system, but not necessarily.
Jerry...you've forgotten more than I know! Here's what I think I know.

The vehicle's starter is signaled from a relay, solely powered by the ESS battery.

Not to split hairs but make a relevant point: like my princess sister-in-law (SIL), the ESS battery does nothing except power devices, some which, through relays, effect the signaling of vehicle components such as the starter (so you're technically correct that the battery doesn't signal the starter, a relay powered by the ESS battery does), just as my SIL only lifts a finger to write checks to others who do the work.

(And yes, my BIL, her husband, is the alternator in this analogy ; - ) )

"And relay operation depends on both batteries"

This is a generalized statement to which I take no issue. Here's my specific point:

The process of getting the starter to "do its things" and crank the engine appears to be effected by a relay solely energized by the ESS battery alone communicating to the starter.

Once this signalling occurs, both main and ESS battery are reconnected in parallel, and the signaled starter then draws its power to start the 3.0L's engine from both batteries.

Some of my statements derive themselves from the, I believe, assumed fact that a 3.0L can turn over just fine with only the ESS battery connected, but not just the main battery connected.

If this is different from what you know, please correct me.

: - )

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Carole1968

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Due to the quantity and length of ESS battery and electrical related threads, researching issues can be time consuming and confusing. I am using this post to make information and related links easily available. This first post will serve as a quick reference and I'll use the second post to provide more details.

JL Wranglers are jump-started just like any other vehicle, except with two batteries it will take more time/power.

On a properly operating system, the batteries are always connected in parallel through the PCR except during an ESS auto stop.

The batteries can go bad independently, but they will run down (or drain) together. Except when a bad battery relay (PCR) or or a blown PCR (ESS) fuse separates them, which will also prevent the Aux battery from charging.

My battery is dead and I can't jump start my jeep
On a properly functioning system the batteries go dead together, so to jump-start a JL you have to overcome two dead batteries. Compared to a single battery system, it will take more time/power to over come two dead batteries. Disconnecting the main battery and jump-starting with just the aux battery should be easier.

My dash is flashing on and off and I can't jump start my jeep
This condition seems to be caused when the Aux battery can provide some, but not adequate power to system electronics, either because it is bad or partially drained. A bad aux battery should be bypassed using a jumper or by unplugging the PCR. Partially drained means either both batteries are drained, or the aux battery is isolated (bad PCR or PCR fuse) and not getting charged. If only the aux is drained, bypassing it with a jumper or unplugging the PCR may be enough to get started, but a jump-start may still be needed. If both batteries are drained, a normal jump-start (more time/power) should be enough.

Bypassing the Aux Battery
A bad or discharged aux battery can affect PCR operation, which can be disruptive to system electronics and it may need to be bypassed. Bypassing can be accomplished by using a jumper wire to connect the main battery directly to the system electronics at PDC terminal N1 or by unplugging the PCR, preventing it from disrupting the system electronics.

Using the Aux Battery as a Dedicated Reserve Battery
A good aux battery can be bypassed and disconnected from the system (by removing the ground cable) to be held in reserve in case the main battery is not able to power a start. A dead main battery should be disconnected from the system before attempting to start from the reconnected aux battery. The aux battery should also be load tested and fully charged before relying on it as a dedicated reserve battery.


3.6L ESS Battery Diagram
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-battery-diagram.14401/

3.6L ESS Aux Battery Bypass
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-aux-battery-bypass.17293/

3.6L ESS Battery Basics
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-battery-basics.20794/

3.6L ESS IBS Information
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-ibs-information.22585/

3.6L ESS Battery Basic Load Testing (Battery Health Check)
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-battery-basic-load-testing.22031/
Just read, thanks.
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
 

Rahneld

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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
Hey @Carole1968. I address your question in another post of a similar thread you posted in today. : -)

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