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3.6L ESS Dual Battery Consolidated Information

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Jebiruph

Jebiruph

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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,
If your batteries test good, talk to the dealer. They may be able to diagnose it without reproducing the problem. I think they can get info from the IBS as to why it goes to battery protection mode.
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Jebiruph

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I'd also like to add that the batteries, I believe, are also isolated just prior to an engine cranking event: be that crank on a cold Wrangler you're first starting for the day, or one sitting in an ESS event at a traffic light, where the light's turned green and the operator has taken their foot off the brake.

In short I'm suggesting that there's this exception to your "except." Fire away if I'm wrong. I'll take the flames so we all get this 411 correct.

At these brief instants, or so I understand it: again correct me if I am wrong, the ESS battery is on its own, isolated, to energize the starter relay to tell the starter to crank the engine, but before doing so mind you, the two batteries are reconnected in parallel so both can provide current to the crank process.
I tested for the batteries isolated just prior to the engine cranking for a cold start and verified it happens. I do not agree with your explanation of why it happens, I posted my explanation here https://www.jlwranglerforums.com/forum/threads/3-6l-ess-cold-start.28297/.
 
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Jebiruph

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My latest update, added descriptions to the links in the first post.

Links to Related ESS Information

(added descriptions to links 05/12/19)
3.6L ESS Battery Diagram
This thread started it all. Due to various conflicting information regarding the dual battery wiring, I made this basic diagram based on information available online.
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-battery-diagram.14401/

3.6L ESS Aux Battery Bypass
An Aux battery bypass lets you start/run with just the Main battery. Handy if the Aux battery is bad or you want to disconnect it to use as a reserve battery.
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-aux-battery-bypass.17293/

3.6L ESS Battery Basics
Here is some basic electrical theory to explain the dual battery system and why it can be difficult to start with a portable battery booster.
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-battery-basics.20794/

3.6L ESS IBS Information
This thread provides information about the Intelligent Battery Sensor that monitors the health of the Main battery. It's this type of sensor that makes ESS systems possible by analyzing the ability of the battery to restart from an auto stop.
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-ibs-information.22585/

3.6L ESS Battery Basic Load Testing (Battery Health Check)
If you're concerned about the condition of your batteries, here's how to check them with a cheap load tester.
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-battery-basic-load-testing.22031/

3.6L ESS Cold Start (added 4/26/19)
Why is the Aux battery so critical to the cold start process? (Critical, but unnecessarily so?)
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-cold-start.28297/
 
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Jebiruph

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Added the following information to the Jump Starting with a Battery Pack using just the Aux battery section of Post #2

(updated 10/03/2019)
Depending on how depleted the Aux battery is, it may jump start quicker using a temporary jumper to provide power to PDC terminal N1 as shown in the picture. This effectively bypasses the pre-start Aux battery power test.
jumpstart aux boost.jpg
 

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Now that the 2.0 T has ESS, instead of BSG, do you think it will be the same as the 3.6 ESS as you have so thoroughly detailed ? Would be nice, two birds with one stone, so to speak.
 

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Now that the 2.0 T has ESS, instead of BSG, do you think it will be the same as the 3.6 ESS as you have so thoroughly detailed ? Would be nice, two birds with one stone, so to speak.
I think it will be similar as other models use the same system, but it's hard to tell. The Cherokee still uses a single battery system.
 
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Here's some better pictures of the PCR location, taken with the fender flare removed. I added these pictures to post #2.

pcr location b.jpg


pcr location 2b.jpg
 
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After first proposing and then discussing using a fused jumper wire to bypass the Aux battery https://www.jlwranglerforums.com/forum/threads/3-6l-ess-aux-battery-bypass.17293/ , I've always assumed that the term "jumper wire" always meant "fused jumper wire" and I have lately been just using the term "jumper wire". I realize now that not everyone could know that a "jumper wire" is actually a "fused jumper wire", so I've made an attempt correct this oversight in the first two reference posts of this thread.

Why I feel it is important to use a fused jumper wire is because the jumper connects Aux battery directly to the Main battery positive terminal. It's been reported that some disconnected Main battery positive terminals have come in contact with a grounded surface. This would effectively connect the Aux battery positive directly to ground which is not good. A fused jumper would break that connection before other damage could occur.

Other precautions can be taken to prevent accidental short circuits, like disconnecting the Aux battery ground, but I will always advocate for the fused jumper. With that being said, I don't think it's a problem using an easy to see clipped on temporary unfused jumper that is immediately removed after using.
 

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I was getting battery protection mode a lot the past two months and thought it was due to the Phoenix heat but yesterday the service start/stop error and battery icon appeared and now my ESS battery and alternator are being replaced. Build date 4/18. 7500 miles
 

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After first proposing and then discussing using a fused jumper wire to bypass the Aux battery https://www.jlwranglerforums.com/forum/threads/3-6l-ess-aux-battery-bypass.17293/ , I've always assumed that the term "jumper wire" always meant "fused jumper wire" and I have lately been just using the term "jumper wire". I realize now that not everyone could know that a "jumper wire" is actually a "fused jumper wire", so I've made an attempt correct this oversight in the first two reference posts of this thread.

Why I feel it is important to use a fused jumper wire is because the jumper connects Aux battery directly to the Main battery positive terminal. It's been reported that some disconnected Main battery positive terminals have come in contact with a grounded surface. This would effectively connect the Aux battery positive directly to ground which is not good. A fused jumper would break that connection before other damage could occur.

Other precautions can be taken to prevent accidental short circuits, like disconnecting the Aux battery ground, but I will always advocate for the fused jumper. With that being said, I don't think it's a problem using an easy to see clipped on temporary unfused jumper that is immediately removed after using.
Like @Tumbleweed..my 2018 sport s has been having battery issues ever since I stopped daily driving it 2 months ago. It sits in the garage a week at a time and wouldnt start a month ago. I jumped it using main battery terminals and it started up. I drove it for 30 min hoping it would charge the batteries. I get a low battery alert when it starts saying battery is low aux switches are disabled. It started the last 2 times I've driven it and the alert pops up...then last night my electrical system went crazy when it wouldnt start and all lights/windshield wipers started going crazy and wouldnt stop even when I tried to power it off. There was a constant clicking in the fuse box that wouldnt stop. I had to disconnect the main battery for it to stop. Would a battery tender fix this or will dealer look at it under warranty? My dealer is a 45 min drive away...so dont want to go there if possible. Do I need a new aux battery? Any help is greatly appreciated!
 
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Like @Tumbleweed..my 2018 sport s has been having battery issues ever since I stopped daily driving it 2 months ago. It sits in the garage a week at a time and wouldnt start a month ago. I jumped it using main battery terminals and it started up. I drove it for 30 min hoping it would charge the batteries. I get a low battery alert when it starts saying battery is low aux switches are disabled. It started the last 2 times I've driven it and the alert pops up...then last night my electrical system went crazy when it wouldnt start and all lights/windshield wipers started going crazy and wouldnt stop even when I tried to power it off. There was a constant clicking in the fuse box that wouldnt stop. I had to disconnect the main battery for it to stop. Would a battery tender fix this or will dealer look at it under warranty? My dealer is a 45 min drive away...so dont want to go there if possible. Do I need a new aux battery? Any help is greatly appreciated!
I suspect the batteries were never fully charged after they ran down. There seems to be a zone between dead and fully charged where the electronics have enough power to do something, but not the right thing - a "dimlight zone" where crazy things happen. Fully charging with a battery charger usually seems to be all that's needed, it will probably need charged for several hours. You might still want to get it checked by the dealer even if after charging everything appears to work.
 

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I suspect the batteries were never fully charged after they ran down. There seems to be a zone between dead and fully charged where the electronics have enough power to do something, but not the right thing - a "dimlight zone" where crazy things happen. Fully charging with a battery charger usually seems to be all that's needed, it will probably need charged for several hours. You might still want to get it checked by the dealer even if after charging everything appears to work.
Thanks for the feedback...apparently driving tje jeep for 30-40 min several times doesnt recharge both batteries. I'm going to buy a battery charger today. To charge the aux battery, do I hook one lead up to the main battery ground and the other positive lead to the 2 studs below that are closest to the main battery? Thanks again!
3IWCv2j.jpg
 
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Thanks for the feedback...apparently driving tje jeep for 30-40 min several times doesnt recharge both batteries. I'm going to buy a battery charger today. To charge the aux battery, do I hook one lead up to the main battery ground and the other positive lead to the 2 studs below that are closest to the main battery? Thanks again!
3IWCv2j.jpg
Just hook the charger up to the main battery terminals, unless something is broken, both batteries will charge from there. I don't know how much driving it takes to recharge both batteries and it is possible your aux battery is failing.
 

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Just hook the charger up to the main battery terminals, unless something is broken, both batteries will charge from there. I don't know how much driving it takes to recharge both batteries and it is possible your aux battery is failing.
I bought a charger and hooked it up to main battery terminals and the repeated clicking started again from the fuse box. Seems like a fuse keeps being tripped. Is this ok to leave it charging with it doing this clicking?


OFr7ly4.jpg
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