More electrical gremlins.

[ShadowsPapa]

Depending on the battery he has it could have safeties in it. Mine has an over volt and under volt shut off. But yeah if I’m right his battery is at least on deaths doorstep

AGM? Never seen an off-the-shelf AGM with anything like that for a starting battery.
Lithium, yes. Those must have circuits to adapt the vehicle charging rates to the battery's needs.
Sounds to me as if he simply bought another AGM main, nothing special or fancy. Those won't have any funky electronics.

In any case, there's a severe issue as the IBS monitors the battery state of charge, temperature and other factors - and if the battery temp rises above a point (I'd have to look up to be sure, can't recall the number now) it will shut things down and you'll see voltage drop to 12.6 - it will in effect shut off current to the alternator's rotor or trickle it to a point where it just maintains needed voltage to keep things going and not add any charge to the battery.

sounds like you have an intermittent ground fault. I.E a big posi wire is grounding and driving load up, alternator steps up to catch load, posi isolates again and the alternator dumps voltage as the load disappears. I'd check and see that your AUX posi cable isn't live and banging around in there or touching its ground sibling while driving

Looks to me from is quote, he never disconnected things down there.......

As far as a cable "bouncing around and touching ground" - he never said he took out or disconnected the cables at the aux battery - only that he pulled the aux ground cable at the main battery.
(Hope he pulled the correct cable! - that varies based on the year!)
Since he has a 2021 - he's in the middle of that change.........

Long story short. Bypassed my aux battery and pulled the negative cable and fuse 42 etc back in Oct / Nov 2024 when the aux battery took a dump and stalled the truck in my driveway at 9V. Then my truck went haywire and voltage on the cluster was 16+ volts and changed the main battery around Jan / Feb 2025 and upgraded to a 94R battery size. All was good after that. No issues

Auxiliary battery ground cable based on year - there was a change during the 2021 model year.........
2020 and I believe early 2021 the ground cable is the small ended cable. Later 2021 and going forward, the cable with the large end is the auxiliary battery ground cable.
You can also tell by the gauge of the cable.

So those disconnecting the aux battery cable ground must make really sure they pull the correct cable.

Many simply pull the ground, pull F42 and move on, aux battery still in place, but isolated by disconnecting the correct ground cable from the top of the IBS.

Sponsored

 

[Lost1wing]

Depending on the battery he has it could have safeties in it. Mine has an over volt and under volt shut off. But yeah if I’m right his battery is at least on deaths doorstep

His battery doesn’t look bad at 12.7 and being fairly new. I think he may have something going on. I went out again just a few moments ago to see how low of a voltage reading I could get on the display and on my meter. 12.2vdc is the lowest. That was with the lights on, fan on high with the engine off. I didn't turn on any heated parts.
He says that the only aftermarket electronic item installed is KC lights. I suggested that they get disconnected for now until he can resolve his issue.
He did the Aux battery delete for a reason. There's no way to tell if he missed something in the process and made things worse or if the original issue is still there. If I was in his shoes, I would disconnect the KC lights. I would fully charge the Main battery and reset the IBS. If that does not work, I would undo the Aux battery delete and restore the electrical to factory. Noting that he would have to recharge the main again.

 

[Lost1wing]

Time to charge 'em - that's only about 50% charged! They should be in the 12.8 territory fully charged, 12.2 is as far down as I'd ever let a battery get. (even an old-school battery)


Did anyone else catch this picture?
How does a Fluke read battery voltage with ONLY the positive lead on the positive terminal of a battery?
What's the Fluke black lead connected to - and if there's nothing on that battery connecting it back to the vehicle, all terminals are removed, how do you read voltage by just holding the red lead on the positive terminal?

Take a look - there's nothing at all connected to the negative battery post - yet he's getting a reading?

I just checked again for what it is worth. The Jeep has been parked for a week without running. I left the key inside and measured the voltage at the battery. 12.66vdc. I opened the door and turned the lights from auto to on. 12.5vdc but recovered to 12.6vdc in a few seconds. I got the key and turned the accessories on. 12.4vdc turned the fan on and the lights on. 12.2vdc yet if I let it sit light that for a few seconds the voltage again recovered to 12.5vdc. I started the engine( no ticking). The dash and meter both said 13.7vdc and 14.2vdc if I bumped the throttle. I pulled it closer to the next available extension cord. It'll be fine.

 

[mtudb24]

AGM? Never seen an off-the-shelf AGM with anything like that for a starting battery.
Lithium, yes. Those must have circuits to adapt the vehicle charging rates to the battery's needs.
Sounds to me as if he simply bought another AGM main, nothing special or fancy. Those won't have any funky electronics.

In any case, there's a severe issue as the IBS monitors the battery state of charge, temperature and other factors - and if the battery temp rises above a point (I'd have to look up to be sure, can't recall the number now) it will shut things down and you'll see voltage drop to 12.6 - it will in effect shut off current to the alternator's rotor or trickle it to a point where it just maintains needed voltage to keep things going and not add any charge to the battery.



Looks to me from is quote, he never disconnected things down there.......

As far as a cable "bouncing around and touching ground" - he never said he took out or disconnected the cables at the aux battery - only that he pulled the aux ground cable at the main battery.
(Hope he pulled the correct cable! - that varies based on the year!)
Since he has a 2021 - he's in the middle of that change.........



Auxiliary battery ground cable based on year - there was a change during the 2021 model year.........
2020 and I believe early 2021 the ground cable is the small ended cable. Later 2021 and going forward, the cable with the large end is the auxiliary battery ground cable.
You can also tell by the gauge of the cable.

So those disconnecting the aux battery cable ground must make really sure they pull the correct cable.

Many simply pull the ground, pull F42 and move on, aux battery still in place, but isolated by disconnecting the correct ground cable from the top of the IBS.

Yup. Mine was built in Sept 2020 as a 2021 model year and have the 2020 terminals as shown above. I have only pulled the negative cable and fuse 42. You can see it tied back to the right of the battery below. Have never touched the positive cable from aux battery

 

[Lost1wing]

Have you checked the negative cable at the fender? I know you have checked the other end at the main negative terminal.​

 

[ShadowsPapa]

@tysongladiator has a great youtube video on checking for electrical "issues"...... based on his personal experiences and observations.
He's also a fun guy - fun to watch his videos.

 

[mtudb24]

Caught it on video today. You can see the varying voltage at the stop light all the way up to 30mph before I turned into the parking lot.

 

[ShadowsPapa]

Caught it on video today. You can see the varying voltage at the stop light all the way up to 30mph before I turned into the parking lot.

Are there any stored codes at this point?
I wonder about the IBS itself failing.

Either of these?
B2193: Intelligent Battery Sensor Internal
U113E: Lost communication with intelligent battery

Or, as someone else said - serious ground loss issue.

 

[kooltoys]

I have a 21 (diesel model) and have charged my batteries several times. to charge the small battery I have had to disconnect all the grounds from the battery. I believe that you have the wrong ground disconnected makin the ground path resistance very high and the BMS is going nuts.

 

[Lost1wing]

Are there any stored codes at this point?
I wonder about the IBS itself failing.

Either of these?
B2193: Intelligent Battery Sensor Internal
U113E: Lost communication with intelligent battery

Or, as someone else said - serious ground loss issue.

I fear that if he keeps driving it like that, he will get stranded somewhere. Back in the day, when we saw voltages that high, the voltage regulator had failed and voltage would follow the throttle. Now that the ECU controls the Alternator output , like you said IBS issue or a ground issue. When he turned, it seemed like he hit a rough spot and that caused the voltage to spike and those other warning lights to pop up. What are the chances that his failed, deleted Aux battery has really failed causing the positive lead on the Aux to short to ground? That needs to be looked at. I believe when a problem arises with the batteries or ESS, the problem should be solved first before the Aux delete. Especially when the Aux isn't the problem.

 

[ShadowsPapa]

I have a 21 (diesel model) and have charged my batteries several times. to charge the small battery I have had to disconnect all the grounds from the battery. I believe that you have the wrong ground disconnected makin the ground path resistance very high and the BMS is going nuts.

If he had the wrong cable disconnected, he'd not have any ground back to the chassis. It should effectively kill the system totally.
There would be no path back to ground - no way back to the main/crank battery for anything.

 

[Lost1wing]

I have a 21 (diesel model) and have charged my batteries several times. to charge the small battery I have had to disconnect all the grounds from the battery. I believe that you have the wrong ground disconnected makin the ground path resistance very high and the BMS is going nuts.

If he had the wrong ground disconnected, the whole Jeep is dead. That is why I asked if he had checked the other end at the fender. A loose fender ground is looking more and more probable.

 

[ShadowsPapa]

What are the chances that his failed, deleted Aux battery has really failed causing the positive lead on the Aux to short to ground?

The aux has no path to ground with the cable disconnected. It's totally isolated, so even if it had a dead short inside the aux battery, it wouldn't matter to the rest of the system.

The aux battery grounds to the chassis ground, using the top of the IBS as a terminal or junction.
Without that cable connected, the aux battery can't have any impact.

If he pulled the wrong cable, then neither battery has a path to the chassis, so nothing should operate.

 

[Lost1wing]

The aux has no path to ground with the cable disconnected. It's totally isolated, so even if it had a dead short inside the aux battery, it wouldn't matter to the rest of the system.

The aux battery grounds to the chassis ground, using the top of the IBS as a terminal or junction.
Without that cable connected, the aux battery can't have any impact.

If he pulled the wrong cable, then neither battery has a path to the chassis, so nothing should operate.

An exploded Aux? A chewed up Positive cable with a roddent completing the path? I've seen some strange things before. He does and did have a large voltage drop. I still think his fender ground needs to be inspected. Do you remember that guy that inspected his fender ground and found it still attatched to the stud with another ground cable, but the stud was sheared off from the fender? I am trying to find that thread. Maybe around 4 years ago is what I remember.

 

[mtudb24]

I have a 21 (diesel model) and have charged my batteries several times. to charge the small battery I have had to disconnect all the grounds from the battery. I believe that you have the wrong ground disconnected makin the ground path resistance very high and the BMS is going nuts.

I have the correct cable disconnected. Mine was built prior to the change in 2021 model year. If that were the case, this would have happened long ago back in Oct / November of last year when I bypassed the aux battery (My assumption is). It wouldn't take this long for the problem to arise. And I have changed my main battery about 4 months ago. and again no issues.

Sponsored