3.6L ESS Dual Battery Consolidated Information

[Jebiruph]

@Jebiruph My understanding from this post is that all the current from a portable battery booster (aka jump starter) can/should go through the aux (aka supplemental) battery. From reading the hundreds (!) of posts generated by your research, I think I saw somewhere else that maybe this is not such a good idea. My jump starter is rated for 1200A peak current and 600 CCA, purchased to supplement a Ford 6.7L dual-battery system, and that seems a bit much for the tiny "Aux14." Not to mention the owner's manual warning above.

You quoted a 3.5 year old post, here's my updated jumpstarting guidance. https://www.jlwranglerforums.com/forum/threads/ess-jumpstarting-main-battery-vs-n1-terminal.87726/

Regarding the 3.5 year old post, at that time (and probably still) people were struggling to get jumpstarted before their booster pack drained down. Disconnecting the main battery helped take some of the load off of the booster. With the main battery ground disconnected, you can still connect your booster to the main battery positive terminal and all those amps will go from there to the starter.

If you connect your booster to the N1 terminal which is connected to the aux battery positive, all those starter amps still go to the starter and not into the aux battery, even though they go through wires that are connected to the aux battery positive terminal.

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[Mainejeepfan]

I have a 2018 jeep jl with the 3.6. I have been having problems with my battery dying I can jumpstart it fine and it will sometimes start up up to a couple hours later without rejumping it again. I tried the AUX battery delete as detailed in the several posts. Tried the Jumper method. pulling the battery and connecting the postive aux terminal to the main battery terminal and the removing the 42 fuse and disconnecting the neg aux terminal on the main battery. Any time I have the Aux battery disconnected the jeep won't start even when I have jumper cables to another car. Anyone have this issue and how did they fix it? ultimately I have a tazer jl mini and have the start/stop feature disabled and I want to remove the aux battery totally anyone have a way to do this that is aware of why my jeep isn't working like others do detailed in this post? Thanks for your help in advance.

 

[Jebiruph]

I have a 2018 jeep jl with the 3.6. I have been having problems with my battery dying I can jumpstart it fine and it will sometimes start up up to a couple hours later without rejumping it again. I tried the AUX battery delete as detailed in the several posts. Tried the Jumper method. pulling the battery and connecting the postive aux terminal to the main battery terminal and the removing the 42 fuse and disconnecting the neg aux terminal on the main battery. Any time I have the Aux battery disconnected the jeep won't start even when I have jumper cables to another car. Anyone have this issue and how did they fix it? ultimately I have a tazer jl mini and have the start/stop feature disabled and I want to remove the aux battery totally anyone have a way to do this that is aware of why my jeep isn't working like others do detailed in this post? Thanks for your help in advance.

It seems like you may have a bad main battery. I would put everything back to the factory original set up and get your main battery tested and replaced if needed. Then get the firmware updated if that hasn't been done yet. Once you get it starting, then pulling fuse 42 should allow you to disconnect the aux battery without the error light.

 

[Mainejeepfan]

It seems like you may have a bad main battery. I would put everything back to the factory original set up and get your main battery tested and replaced if needed. Then get the firmware updated if that hasn't been done yet. Once you get it starting, then pulling fuse 42 should allow you to disconnect the aux battery without the error light.

Just wanted to update this and thank you for your input, this was exactly it. I replaced the main battery and did the aux removal and the whole thing worked as it should. Thanks for your help it was acting weird in this was my first experience with battery issues with the jeep platform.

 

[Jebiruph]

Just wanted to update this and thank you for your input, this was exactly it. I replaced the main battery and did the aux removal and the whole thing worked as it should. Thanks for your help it was acting weird in this was my first experience with battery issues with the jeep platform.

Thanks for following up, it really helps with the knowledge base when the fixes to problems are posted. I'm glad you got it fixed.

 

[xylodan]

Well it has happened again. Both batteries needed to be replaced again (under warranty). First at 12 months and now at 21 months 20,000 miles.

Happened to me today. 18 months and 20k miles on my diesel.
I'm surprised to learn I might get warranty help after reading these threads. I'll call the dealer tomorrow.
I was here researching what batteries to install but maybe I won't have to.

 

[Bob Burd]

I've pulled F42 and removed the negative of the aux battery, now just running off main. I'm wondering if I can use the aux (kept periodically charged) as an emergency battery if the main dies. I would disconnect the main negative, reattach the aux negative to the body ground wire, then give it a go. From the wiring diagram, it appears that this will force the starter current through a 150A fuse on the high current fuse array. Does anyone know how much current the starter will draw? I don't want to sacrifice (yet another) fuse array just to try this out...

Edit: It looks like it could be anywhere from 150-250A based on research, so I don't suggest anyone try this. You'd probably want to jumper that high current fuse out of the current path.

 

[andy29847]

Hopefully, I have completed my 6-month odyssey with battery problem in my 2020 JLUR. I thought I would share my experiences here on a chance it might help someone with similar struggles.

The first thing I learned, starting back in OCT 2022, is I am not as smart as I thought I was. The thought processes and experience I had with single battery systems did not transfer well to my Jeep JL. Second, Jeep uses cheap batteries. Third is that the techs at the dealer that worked on my Jeep were not trained, or did not understand their training, regarding the stop start system. A recurring thought I had during this fun was that the systems on my Jeep should be telling me more about what was wrong.

I bought my Jeep in October 2022. It is a 2020 JLUR and it had 35,200 miles. I bought it as my 70th birthday present. I bought this one because it has a Power Sky Top. I bought it at a Ford dealer, but the Jeep had originally been sold at the nearby Jeep dealership. The new Jeep was my 3rd Jeep. I sold my TJ to buy this Jeep. I also have a 2020 Gladiator.

A week after I bought the Jeep, I got a warning message - Stop/Start not working, Battery charging. I did enough research to determine that my batteries were covered by my warranty and then visited my dealer. This is what they wrote.

It worked for a couple of days and I got the battery charging message again. I went back to the dealer. They did nothing promising.

The stop/start worked for 1 day this time. Back to the dealer. On the third visit, they put in a new main battery.

The next day I got a "Service the Stop Start system" message. I returned to the dealer. The tech wrote up some stuff which I believe was done to just pad his time. I mean really, corrosion on the positive terminal of the new battery. That makes me laugh.

After the 4th visit, the stop start system on my Jeep was WORKING. By this time I was watching the system like a hawk. One thing I noticed was that the system always charged at 14.7. I deduced that this was because the auxiliary battery was nearly 3 years old. I decided to delete the Auxiliary battery using the "Jumperless" method. This seemed to work. Charging voltage now started at 14.4v and after 30 minutes would go down to 13.9v. I thought this was OK. This Jeep is not a daily driver and I only use it once or twice a week.

By the time I got to this point, I figured I had become an expert on the Jeep battery system. I read most of the "battery" threads here and often commented. One thing I was doing was tracking the readings on my dash voltmeter. On one thread, I advised another owner to use his dash voltmeter check the voltage of his main battery. You can do this by disconnecting the auxiliary battery by setting the Jeep in "Run" without the cranking the engine. Anticipating that the guy I was trying to help would comply, I went outside and checked mine to have my numbers ready for comparison. You can imagine my surprise when my dash voltmeter showed just 12.1v. I watched the voltmeter as I cranked the truck. Battery voltage went down to 11.7v. Then I disconnected my battery and tested it with my voltmeter. The handheld meter showed 12.48v. I shared my info, including a photo of the battery my dealer had installed. One of the Gurus here, Rhinebeck01, commented that my new battery was not an AGM. If you don't know, JL Jeeps come with AGM batteries, not flooded lead acid batteries. The means that I had some battery problems. First, the dealer should have replaced both batteries when he replaced the main. Mixing old and new batteries is not good. Second is that charging voltage in the ranges I had been seeing (14.4 - 14.7) are good for an AGM battery, but can damage a flooded lead acid battery.

I called my dealer to complain. They did not respond at first, but after I talked to the General Manager, they started to listen a little better. The deal I worked was that I would take my Jeep in for a battery change. They would change both batteries. They would have a guy waiting to do the work when I got there. But wait! The fun wasn't over. When I signed my Jeep in, I told the service advisor that I had the auxiliary battery disconnected because it was bad. I told him the negative cable was tied back, and the fuse (F42) was in the glove box. When I got the car back, the display was showing "service the stop start" and the spaceship A light was lit. I didn't want to go back inside, and I guessed that the tech had not connected the auxiliary battery, so I drove away.

At home, I found that the dealer tech had put in the F42 fuse, but he had not connected the auxiliary negative cable. I connected the cable but the alarm did not clear. Then I disconnected both negative cables and unplugged the IBS for 15 minutes. When I hooked everything back up, the alarm was cleared. All is well in Leadville.

Phew! I hope I never have to go through this again. I am now running both batteries. The dash voltmeter is reading normal levels now. It is at 13.7v after the first crank of the day. The voltmeter goes down to the low 13s not long after cranking. I've even seen it at 12.8v a couple of times.

God luck if you are having trouble.

 

[VKSheridan]

Your experience is similar to mine Andy with the exception of mine stranded me twice. My local dealers are equally lacking in diagnostic skill so I’ve refrained from giving them a chance to break something else while they threw parts at the situation.

I really wanted to figure this thing out but I yielded to conclude the reserve capacity of the lil’ auxiliary battery is simply inadequate to keep the controllers properly energized for any extended amount of time.

I replaced my auxiliary battery twice and interestingly, both were able to be revived by my NOCO Genie10 and I use them as camping power supplies. They’re not bad in that application.

What I think (too tired/lazy to confirm) is happening is the controllers are (rightfully) kept energized by the lil’ battery and slowly reduce its voltage. Once the voltage hits “x”, the controller(s) go nuts from inadequate power and turn things off/on which further taxes the battery until it’s state of charge is unrecognizable by the IBS when connected in parallel with the main battery.

I pulled the auxiliary battery, pulled the fuse, taped the ends and my Jeep (finally) can be parked for more than a week without the need for a maintainer or jumper cables.

Why this phenomena affects only some of us and not all of us is a mystery to me. We seemingly have an unrealized option or antagonistic part build series in common. Good luck!

 

[andy29847]

Why this phenomena affects only some of us and not all of us is a mystery to me. We seemingly have an unrealized option or antagonistic part build series in common. Good luck!

Have you read about the RVers who tow their JLU Jeeps w/LED tailights finding their Jeep batteries dead at the end of a long day? It seems the light circuits have a sensor that wakes up the lights when triggered. I'm wondering if there is a commonality with the problems of the Jeepers who do not tow their Jeep.

Here is a post from an RV forum that I have saved: https://www.irv2.com/forums/f85/towing-a-jeep-wrangler-603165-2.html#post6415836

 

[VKSheridan]

I am indeed aware of it

In many cases, the dead battery is because their brake lights energize every time the supplemental brake is actuated. Of course, every time the brake pedal is depressed, the Jeep thinks someone is going to hit the start button and controllers have several circuits energized.

The other contributor is when folks rely on diodes alone in the turn/tail circuit. Diodes prevent backfeed to the coach but they don’t isolate the coach’s signal from the Jeep. I’ve seen dash lights illuminated on Jeeps in tow and you know that can’t be good!

For my rig, I installed a relay that isolates the brake/tail/turn lights when connected to the coach. When connected, voltage from the 7th pin on the coach’s pigtail energizes the relay that connects the coach’s signals to the rear lights. When energized, the 4 wires from the Jeep to the lights (including the license plate light) are open and the signal circuit from the coach are closed. When de-energized, the circuit is restored to original configuration.

Some folks use toggle switches, some use diodes. I prefer full isolation via relay so that if an electrical problem occurs, the coach doesn’t smoke the Jeep and the Jeep doesn’t smoke the coach.

Unfortunately, my battery woes existed the day I drove my Jeep home. The infamous “Auto-start Not Ready” was lit and the dealer said it just needed to charge. My battery woes ended when I went camping……LOL

 

[troverman]

What I'd like to know is simply WHY this start-stop system needs to have the second battery and somewhat complicated setup. I've seen dozens of vehicle from other manufacturers with auto stop-start and they simply use the normal, regular battery with no aux battery. The systems work every bit as good as the Jeep system. And frankly, the battery in my Jeep is either 630 or 650CCA - way more than enough for the little Pentastar V6. Heck, dad's F-150 with the V8 uses just one 750cca battery and it has a stop-start system which works fine. ANother relative has a late model VW that only uses a single battery but has this system. I just don't know what the advantage of this second small battery is.

 

[andy29847]

I hadn't seen one of the Jeep Auxiliary batteries until I removed the one from my JT today. I've been running the jumperless bypass for several month on the old Mopar main battery. A couple of day ago I installed a new Everstart battery from Walmart. This morning I took the old auxiliary battery out of the truck.

I removed the cables from the main battery and insulated the ends. Jacked up the passenger front and removed the wheel. Removed 1 bolt and 2 push pins and I was able to fold the fender liner back enough to access the battery. The battery box is put together with 3 bolts. I removed those, supporting the weight of the battery as the bolts came out. The bottom of the battery box slides off and the battery is exposed. All of the screws in this procedure come out with a 10mm socket (I found it!). I taped up the ends and folded them into the box so they would stay separated. The positive end is 2 cables spliced together at the battery connector. These cables need to stay together.

The Mopar H7 battery, the one that comes with the tow package, is 700 cold cranking amps. The Mopar auxiliary battery is 200 cold cranking amps. The new Everstart battery I installed is 850 cold cranking amps. The small amount of power difference is well worth slight loss of power considering the simplicity of running just one battery.

This is the Mopar auxiliary battery that came out of my Jeep.

This is the Mopar main battery

]


This is my new battery.

 

[Acme]

Hi. Another ESS question/situation. I haven't read the whole 13 pages but I did read the 1st post and have a basic understanding of how the system works.

Now... my situation. After 2 days offroad we stopped at a gas station, I filled up, then started the JLU a first time to move to a parking spot to talk with my friends. We were there for 5 minutes. Then we left... at the gas station exit, I came to a stop to let some trafic go... my JLU stopped and wouldn't start again. There were messages on the dash, but I had people behind me so I didn't have all the time in the world... I ended putting it back into park, turn it off, then proceeded to a "normal" start... it did... and I left. All was fine, but I had a check engine light, and the light that says ESS is not working (A!).

I stopped. Scanned with JScan... we were in a hurry. I didn't think to grab a screen shot. Basically I had a few codes not relevant to the situation (TPMS, blind spot sensors, etc.) but one "extreme low voltage detected"... I cleared them thinking they would simply come back. We left... no more lights. I drove for 4 hours without issue (with auto stop-start turned off just to be sure).

This morning I went for a drive to test... no lights... but no ESS. It just doesn't work. I have no messages, no lights. Both batteries read 12.5 - 12.6 volts when tested individually. While driving, the cluster shows the battery voltage to be between 13.5 and 14.5. Looks..... fine.... to me.

I also tested starting the Jeep 5-6 times in a row in my driveway, there's plenty of juice and no hesitation.

So... What happened/is happening?

I was expecting one of the batteries to read low, but it doesn't.

It's a 2019 JLU V6. I think both batteries are the original ones, but I can't be sure as I bought it used 2 years ago.

Any idea? I'm planning on bypassing/removing the aux battery, but I would like to understand what could be the issue. I don't care about ESS, I hate the thing with passion.

TIA

 

[WranglerAz]

It's a 2019 JLU V6. I think both batteries are the original ones, but I can't be sure as I bought it used 2 years ago.

Any idea? I'm planning on bypassing/removing the aux battery, but I would like to understand what could be the issue. I don't care about ESS, I hate the thing with passion.

TIA

I removed some of your post just for brevity of the quote. My opinion is you should replace both batteries, or do as I (and others) have done and route the cables to just run off one new H6 replacement and ignore the mini battery. There are forum threads on how to do this.

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