DIY How-to: Take the Aux Battery Offline

[Dryfly24]

If I were to do this mod - I'd right away opt to replace the main battery with the biggest battery that will fit that tray, and the highest Ah available in that size.
You will be running everything from that one battery, so the "millions of ...... are operating on one battery" while true, is not the whole story - they will have a larger "one battery" because now, everything is depending on that one battery. And if you have after-market parts installed like lighting and other fun stuff - the charging system may not keep up at idle so you need the batter as a backup.

Way ahead of you. Bought the biggest, baddest one they had. Now I just need to do this mod.

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[ShadowsPapa]

Holy cow mate, it was a bad analogy about a remote. No need to quote it twice lol. My point was to counteract the screaming voices saying that the system is flawed and that a dead aux WILL kill the main. Something you’ve said many times on here.

I.e. we agree, I think.

Yeah, it's true that the 'it WILL happen" is false but people will see the "it can't happen" and then be confused if they have the worst luck in the world and it does.
The point is - get out facts.

I think the real point is - jeep batteries are not good batteries right out of the factory.
jeep batteries fail in short time - in general, today's factory installed batteries fail in short order (4 years is a good life these days) Jeep batteries are worse - life of 2.5-3 years is good.

And I go back to - if the aux is the bad guy in Jeeps - why do the 4xe Jeeps see a lot of failed batteries?
There is NO aux battery!
Yet they fail at the same rate as the batteries in our JTs - So stop blaming the aux battery!
Jeep batteries fail - and quite often both fail at about the same times, thus the myth.

Knowing the facts, I see no need to do this, there's an extremely small "risk" at all and the ability to jump start these is still there.

 

[Dryfly24]

BTW, for any of you other clueless wonders like me who don’t know what IBS stands for. I had to Google it: https://www.jlwranglerforums.com/forum/threads/3-6l-ess-ibs-information.22585/

 

[ShadowsPapa]

BTW, for any of you other clueless wonders like me who don’t know what IBS stands for. I had to Google it: https://www.jlwranglerforums.com/forum/threads/3-6l-ess-ibs-information.22585/

Only install the IBS on a fully charged battery.
Always fully charge a new battery BEFORE installing.
Reset the IBS (leave it disconnected for at least 10 - 15 minutes) before reinstalling on a freshly charged new battery.

When charging in-vehicle batteries, charge through the IBS, not directly to the negative post.

 

[Dryfly24]

1. Without being grounded the battery can't be a battery, dead or alive.
2. I have seen numerous first hand real world accounts of that happening. I trust that under the right circumstances it can occur. Why take the chance when you don't have to?
3. There's no way to know for sure until they are separated, charged and tested separately. The great flaws in this setup are that
A - One battery can take the other one down with it, and you won't know until it's likely too late.
B - The electronics do not monitor both batteries independently.
C - Access to a consumable like the AUX battery should be vastly better. There are two ways of getting to the battery, which absolutely positively without a doubt WILL need to replaced at some point, and neither of them are Advance Auto parking lot easy.

The only thing you really lose from taking the AUX battery out of the picture is the increased risk of failure. Millions of cars on the road with one battery and advanced electronics.

Seems like all of this drama, debate, bickering and stress could be quickly resolved by simply making the aux and main easily accessible, and designing the system so you could test each battery individually. That way you could just replace either/or as needed.

How firkin hard could that have been Jeep?

 

[ShadowsPapa]

Seems like all of this drama, debate, bickering and stress could be quickly resolved by simply making the aux and main easily accessible, and designing the system so you could test each battery individually. That way you could just replace either/or as needed.

How firkin hard could that have been Jeep?

Yeah, you have a point.

It's not THAT bad to access if you go through the wheel opening - one guy showed you don't eve have to pull back the whole liner. He showed how easy it was in a video. Still, though, not as simple as opening the hood, especially when out in the sticks and rocks.

To test you have to at least pull the ground cables apart from each other - but that's not easily done in the field either as you won't have the equipment - you can pull the cables apart but that's about it.
In my shop - it takes just a few minutes - pull cable off IBS, take cables apart from each other, test batteries.
You could do what some clever members have done - go to Amazon, buy a pair of bluetooth volt meters and place one across each battery so you can watch the voltage of each on an app on your phone.
I've made connections to each battery so when I'm in an ESS stop event, I can see the voltage of each battery independently and see how each reacts.
People say that "oh, that aux battery bears the load in an ESS stop so...........
Uh, no. It carries SOME of the load - the electronics in the vehicle but not all of the electronics. The main battery still handles the fan, EHPS and other stuff and you can watch both batteries drop at about the same rate if they are both healthy and both about the same age.
In other words, Jeep did a good job splitting the load across the batteries so that when one drops to 12.3, for example, the other one is right about there as well.
that means Jeep has done a lot of math and figured with two healthy batteries of the capacity they installed with the factory loads - each will be cycled about the same during a stop.
That's why when one goes, the other is likely ready as well - not always, "it depends" but on a purely stock Jeep - both batteries go down or are cycled about the same during an ESS stop. Voltage on both batteries drop, and they drop at similar rates.
So the info you see online about this stuff out there is wrong. The load is distributed across the batteries - From each according to its ability, to each according to its needs.
Proven with volt meters on each battery during multiple ESS stop events and via the schematics of these Jeeps.
(but no one bothers reading the owner manual, let alone look at schematics or test anything)

 

[Lunentucker]

If I were to do this mod - I'd right away opt to replace the main battery with the biggest battery that will fit that tray, and the highest Ah available in that size.
You will be running everything from that one battery, so the "millions of ...... are operating on one battery" while true, is not the whole story - they will have a larger "one battery" because now, everything is depending on that one battery. And if you have after-market parts installed like lighting and other fun stuff - the charging system may not keep up at idle so you need the batter as a backup.

Could you maybe call Jeep tomorrow? ?

Anecdotal - The red light was blinking on the Honeywell Redlink remote thermostat sensor on the dresser the other night after I got in bed. I was afraid to risk it all night, given the stifling Virginia heat and humidity, so I waddled downstairs and pulled TWO brand new AAA's from the drawer beside the sink and replaced them both fresh hot coppertops.
Getting stranded up there was not a risk I was wiling to assume with replacing just one of them.

 

[EricStanley]

I sorted out which negative cable to remove (see above re: 2020 vs 2021+) and pulled the fuse. Cool. Except yesterday ESS worked out of the blue. The engine shut off at a stop light and it restarted immediately after taking my foot off the brake. The electronics (head unit, dash, etc) all turned off while it was restarting. I had thought that pulling the fuse would prevent this from happening. Surprise! It doesn't. I have confirmed that I pulled the correct fuse (putting it back in results in getting the error in the display, removing the fuse again and the error goes away).

Related, but only slightly... I do have a Tazer Mini installed and it doesn't seem to auto-recall the last setting of the ESS button on the dash with any consistency. Meaning I can disable the ESS using the button (light comes on), then turn the truck off. Come back later and start the truck and ESS is enabled again (light is off). This was the condition yesterday when ESS kicked in. I hadn't noticed that the light was off until the engine shut off (and turned back on after lifting my foot off the brake) and then I looked at the button surprised to see that it hadn't kept the previous setting. I tested it a couple times yesterday and today and sure enough it sort of sometimes recalls the last setting and sometimes doesn't.

 

[ShadowsPapa]

Except yesterday ESS worked out of the blue. The engine shut off at a stop light and it restarted immediately after taking my foot off the brake.

Yes, exactly. As I said in an earlier post in this thread - it doesn't disable ESS. ESS will function properly for roughly 6 stop events.
Removing the fuse only prevents the error on the dash - not a thing more! It prevents the PCM from opening the PCR and doing an aux battery test. With the PCR closed during the startup test, it sees the same voltage there as at the main and ESS works. However, because the voltage is identical it does seem to cause it to stop working after about 6 stops.

The subject line is misleading as this only takes the aux battery out of the system, it doesn't prevent ESS from working.
Again, pulling the fuse only prevents the error on the dash, nothing more or less.

 

[KevinM60]

Only install the IBS on a fully charged battery.
Always fully charge a new battery BEFORE installing.
Reset the IBS (leave it disconnected for at least 10 - 15 minutes) before reinstalling on a freshly charged new battery.

When charging in-vehicle batteries, charge through the IBS, not directly to the negative post.

The last part of those bullet points has me a little confused.
It says ". . . requires charger or tester to IBS (B-) post"
Next one says "connecting to (B-) creates "blind charging"
and last says "do not blind charge"

I plan on using a battery tender on mine because I only drive it on weekends and want to keep the batteries strong.
To simplify things, the diagram below is from that earlier IBS link.
In that view would I clamp the negative from the tender to the Main negative to get it to run through the IBS correctly?

 

[ShadowsPapa]

The last part of those bullet points has me a little confused.
It says ". . . requires charger or tester to IBS (B-) post"
Next one says "connecting to (B-) creates "blind charging"
and last says "do not blind charge"

I plan on using a battery tender on mine because I only drive it on weekends and want to keep the batteries strong.
To simplify things, the diagram below is from that earlier IBS link.
In that view would I clamp the negative from the tender to the Main negative to get it to run through the IBS correctly?

Connect a charger or tender to the stud (as in the green circle)
Not to the area with the red X (not to the negative battery terminal or the IBS clamp on the battery terminal)

 

[KevinM60]

Connect a charger or tender to the stud (as in the green circle)
Not to the area with the red X (not to the negative battery terminal or the IBS clamp on the battery terminal)

excellent!!
Big difference between the two.
Thank you

 

[Gezer]

I will be at 4 years this month on original batteries. Interesting your info on the battery draws. If I change both batteries but change the main to a bigger better battery will that change how the batteries work together? most auto electrical is a mystery for me. Thanks.

 

[ShadowsPapa]

I will be at 4 years this month on original batteries. Interesting your info on the battery draws. If I change both batteries but change the main to a bigger better battery will that change how the batteries work together? most auto electrical is a mystery for me. Thanks.

Should make no difference since they are actually charged in parallel in the end. Levels will even out when parked.

 

[Dryfly24]

So went out to my truck this morning to take my dog on his daily hike and - yup, you guessed it - dead battery.

About to to try this aux battery delete. I’ll let you guys know how it goes…

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