Batteries - let's figure this out.

[Andy29847]

I've recently had some battery trouble. I went to the dealer because my Jeep was still under warranty. It took 3 trips to the dealer to resolve the issue. While the dealer worked on my Jeep, I studied the threads here. First impression? Durn, this battery poop is complicated. Even the dealer with all of his fancy tools and training has trouble. Anyway, we should be able to develop a guide/flow chart to help other members here. I'm going to start by listing the possible factors for failure and then sharing my experience.

problems:
Jeep will not start
Stop/Start will not work
Batteries will not charge

components
Main Battery
Aux Battery
Intelligent battery sensor
Fuses
Relays

complicating factors
system parameters (them durn black boxes)
special procedure for jump starts or for charging batteries

easily available info
charging voltage (from the driver's display)
voltage of system before start (from the driver's display, preferably after sitting for the night)

I saved this drawing from my research. I wish I knew who developed this so I could give him/her credit. It's good!

My Stop/Start-Remote Start quit working. I checked the voltage of my batteries before start using both screen 2 on the driver's display and with a multimeter. I also separated the batteries and tested them with my multimeter. My batteries tested at 12.4 volts, i.e., they tested good. Good meaning that the voltage was at an acceptable level for 2.5-year-old batteries.

The first trip to the dealer they tested both batteries, found them good, and replaced the Intelligent Battery Sensor. The Stop/Start worked the first day but quit again on the second day. This was the dealer's comment:

Note that the IBS level the dealer's tech commented on is roughly equal to 12.4 volts form the batteries.

I did not get a report from the second visit. I waited at the dealer while they worked on my car. The Service manager told me that they charged the batteries through the Intelligent Battery Sensor. The Jeep passed the test drive. The Stop/Start worked that day. It would not work after the first night.

My dealer said all the right things and had a good attitude when I called the 3rd time. He asked to keep the Jeep several days and promised to assign a level 3 tech to the job. I gave them the Jeep for a week. This was the report:

They replaced the main battery. The Stop/Start has been working for a week. My conclusion? The Jeep system parameters are set so that a good used battery would not work.

General thoughts form my experience and research?

Stop/Start problems are caused from the main battery.

No start problems are caused by the aux battery.

The Intelligent Battery Sensor is not really intelligent.

The only generalization that is true is that no generalizations are true.

Things I don't understand (not everything ) - Variations of the charging voltage. I've seen 14.7 and 12.8 and everything in between.

 

[Mister Lamb]

All of these electrical issues for a feature most people disable at start up.

Thank you Green (Socialist) Initiative

 

[COmtnbiker]

I'll add something that happened to me with Stop/Start. Mine stopped working for a few months.
Then one day I had to drive about an hour out of town. It suddenly started working again ON that trip towards the end. It's worked ever since.

I think my Stop/Start issue was due to a low battery, that needed a longer drive to charge.

 

[Rahkmalla]

my ASS system freaked out Friday morning. ASS not working warning and charging system error warning. Driving voltage was 11.8. Oh shit, i'm preparing myself to be stranded at any second on my drive to a big meeting. My dealership is about half way between my house and the meeting site (not even a diversion I pass it all the time). So i stop in, ask about loaners and schedule an appointment.

By the time i get back out to my truck and start it up, it's working again. Driving voltage 14.3+

For what's it's worth, the first thing i did when i saw 11.8 while driving (after seeing ASS broken) was pull over and give the truck a restart. Didn't work that time. Haven't had an issue since, but that was only a week ago. I'm looking forward to the impending headache...

 

[jebiruph]

I saved this drawing from my research. I wish I knew who developed this so I could give him/her credit. It's good!

That's my drawing, there's more information here https://www.jlwranglerforums.com/forum/threads/3-6l-ess-dual-battery-consolidated-information.25377/

 

[coppertales]

New guy here with a battery problem with my 2020 Gladiator. The truck was in storage for a year. When I went to start it, the battery was dead, which I expected. I went to charge the battery and found out the battery would not charge so I replaced it with a high end battery. Life was good for about two weeks. Then, the car would not start, battery dead. Charged up the battery and everything worked. The next morning the battery eas dead. Again, charged the battery. I then found out Gladiators have an aux battery. So, the truck is now at the local dealer for a fix, I hope. I can visualize them replacing the two week old new battery and charging me an arm and a leg. When I was setting up the service, I found out the truck's warranty had expired two weeks ago. Bummer. I guess I will have to bend over and take it when I get the repair bill. I am an old time Pontiac trained mechanic but I cannot work on new vehicles plus, I am an old guy now.

 

[Andy29847]

That's my drawing, there's more information here https://www.jlwranglerforums.com/forum/threads/3-6l-ess-dual-battery-consolidated-information.25377/

Thank you for the work you and done and for sharing it here.

 

[ShadowsPapa]

General thoughts form my experience and research?

Stop/Start problems are caused from the main battery.

No start problems are caused by the aux battery.

The Intelligent Battery Sensor is not really intelligent.

The only generalization that is true is that no generalizations are true.

Things I don't understand (not everything ) - Variations of the charging voltage. I've seen 14.7 and 12.8 and everything in between.

LOL - there's so much speculation and guessing and - ahem - generalizations there.
At 12.4 your AGM battery is actually quite low. And it VARIES with the battery and temperature.

This here - sorry, for those with virgin ears - this is BULLSHIT ->

In fact, that is SO wrong FCA has a bulletin addressing the idiocy of such "techs".
I should dig up that clown's address and mail him the FCA training materials and the bulletin that says do not replace the IBS - RESET IT.

It's so very simple and yet you get people like that - and then that crap gets posted and reposted and it's wrong. "but a tech said so" is almost as funny as the term "Senate intelligence committee".
This is partly why the web is so messed up as far as finding any decent information on these things.
Did that guy use the proper, correct, procedure for testing batteries? I doubt it.
Worse - charging both batteries, still in parallel for 30 minutes very well may only get you up to 54% -it can take hours to correctly, properly, fully, charge just the crank battery to 100% and he figured 30 minutes was enough?
I've seen it take 30 minutes to go up 20% on just the crank battery alone.

Please don't base anything you think you know on what that tech wrote. If I saw that on my invoice, I'd have a talk with them and when I got the 'how was your visit' survey - I'd likely give them 0s and no more than 5s.
When a tech says that "your winch was draining your batteries" - ignoring the big RED switch sitting right next to the battery that was OFF, and then saying he "fixed it" by moving the winch ground cable from the top of the IBS over to a chassis ground - the same ground stud that the big black cable from the battery post goes to, I know we're in deep doo-doo Jeep dealership-wise. (not to mention the winch is actually connected to the negative by virtue of it being bolted to a plate that's bolted to the frame anyway)

My batteries tested at 12.4 volts, i.e., they tested good. Good meaning that the voltage was at an acceptable level for 2.5-year-old batteries.

Not IMO - that's low, and anything from 12.4 on down can cause ESS to not work.
Some charts show 12.4 as being 50% or less. You consider that good? That's actually pretty bad in my training. Look at this - even 12.5 is RECHARGE RECOMMENDED and you suggest it's acceptable.

From a STAR training bulletin, part of their chart showing when ESS will work -

so if you are at only 60%, then ESS won't activate. Hmmm, that's around 12.4 volts give or take.

No start problems can and often are caused by the main/crank battery. That's been proven/demonstrated if you had seen recent posts.
Stop/Start problems can be caused by EITHER battery. If the PCM's quick check of aux battery on initial start shows low voltage it won't shut down at a stop light.

You can't go by some of the stuff you see on the web - because it's guess work done by people who don't understand. They had a problem, they did something, it worked, so now they have it all figured out. They post about it, 10 people see that and copy the posts out to other places, suddenly all of the world's problems are solved.
Fact is - either battery can go bad. Either battery can thus cause ESS issues. Either battery can thus cause a no start issue.
"the internet" is always looking for easy answers and people, being people, prefer simple, easy solutions to what they don't understand. So you end up with a lot of crap on the web.
Jerry has done more digging - the others, sorry, are hacks.

Let's not get more bad info out there - meaning more speculation and guess-work. There's so many of these threads and most have info that's, well, less than good, less than correct.

As far as charging voltages, that's simple and I've covered that ad nauseam -
Batteries need a higher charging voltage when the temperatures drop below roughly 70, depending on the battery, etc.
In fact, systems in the 1960s made by Motorola had a thermister - a temperature compensating circuit inside their solid state regulators that increased the regulated voltage in colder temperatures (I have the charts in my college and training docs that give details)

(A shot of a circuit I am working on to replace those on classic cars - I have it regulating at 14.1x volts at 68 degrees )

The normal charging voltage for a legacy wet lead acid battery was 13.8 to 14.2 (varied a bit with the company) When the temperature dropped, the voltage goes up. Chemical reactions don't happen as easily when it's cold and a battery is a chemical reaction in a case.
These can show voltages as high as 14.8 to 15.0 when it's in the 20s, and high 14s isn't unusual.
When the batteries are hot, a nice warm day, and are "fully charged", the voltage is cut, sometimes as low as 12.7 or so. That saves parasitic draw on the engine. Why load up the alternator when the battery is charged - and more - when the battery is hot don't make it MORE hot with higher voltages.
You may also see the voltage vary with engine load. The PCM calculates the torque and when coasting down a hill you may see the voltage climb, then going up the next hill, it drops again. You can watch all of this with a good piece of software - monitor the torque and voltage and you see an inverse relationship.
Heat kills batteries, so the PCM, knowing from the IBS what the battery temperature is and what the SoC is, cuts the voltage to help prevent over-heating.
There are TSBs and other bulletins and training materials out there on the IBS, charging rates (which I've already posted a copy of the charging rate bulletin)

The problem with the IBS is most often owner abuse and negligence. People don't get it, they jump wrong, they charge wrong, they swap batteries incorrectly thinking they know, or they do it like they've always done (which is often wrong) and assume you can still do the same today.

I'll add something that happened to me with Stop/Start. Mine stopped working for a few months.
Then one day I had to drive about an hour out of town. It suddenly started working again ON that trip towards the end. It's worked ever since.

I think my Stop/Start issue was due to a low battery, that needed a longer drive to charge.

These don't take kindly to sitting around for days, or SHORT drives.
These don't make good commuter vehicles where you drive 20 minutes to work and shut it off. That's a bigger part of the issue than the design itself.
If the truck sits days at a time, or your drives are typically only 20 to 30 minutes, you should look into a battery tender (and use it correctly - charging THROUGH the IBS, not bypassing it)

I am an old time Pontiac trained mechanic but I cannot work on new vehicles plus, I am an old guy now.

SOME of what you learned and used may well carry forward - a lot doesn't.
There's a label on the negative cables going to the crank battery negative post explaining about the other battery and that to TRULY have things disconnected, you need to separate the cables that go to the negative post on the crank battery. Not doing so and you can create a situation where you blow the fuse that handles charging to the aux battery............

The problem is that the facts on these, the training materials on these, and batteries and charging systems in general occupies hundreds of pages but people want a simple answer - not having to learn each part. So stuff gets assumed or even made up.

(I think we're up to thread 86 on "how this works" - sadly, not all of it is correct)

No offense, but there's just no way you are going to have any simple flow chart on this. Not when there are dozens of training documents, even books, out on batteries, charging systems and so on. It really wasn't even that simple 20 years ago. You aren't going to boil this down to a single page simple chart.

 

[Rockabillyroy]

My auto stop start stopped working a while ago. Never really gave it much thought. Then I started monitoring the voltage while driving. It seemed to stay high.

So I replaced both the aux and main battery. The old main and aux read 12.4 and 12.3 respectively. Topped them both off before installing. It took a couple weeks, but my auto stop start has been working again since. And my running voltage has been lower.

That being said, when auto stop kicks in, the voltage reading on the dash will drop below 12v at times.
Which isn't the case when I read them with the multimeter with the truck off.

 

[ShadowsPapa]

General thoughts form my experience and research?

Stop/Start problems are caused from the main battery.

No start problems are caused by the aux battery.

The Intelligent Battery Sensor is not really intelligent.

The only generalization that is true is that no generalizations are true.

I'll shorten and address only your generalizations - almost all incorrect:

Stop/Start problems are caused from the main battery.

start/stop issues can be caused by EITHER battery. (Sorry, you got bad info - but that's not unusual taking it from the web)
If the aux battery is not up to snuff, ESS won't function (and in fact there's a very long chart on other reasons)

No start problems are caused by the aux battery.

Nope. Can be caused by either, can be caused by the main battery being bad just as easily. In fact, forum members have proven this in just the past few days. Either battery can go bad. Even the crank battery. If it dies, if the voltage is below a certain threshold set in the program parameters, the system will deny start attempts.

The Intelligent Battery Sensor is not really intelligent.

That IBS is a SENSOR only. The intelligence is in sensing. It makes no decisions. The PCM does.
The IBS feeds the PCM information via the LIN (a bus)
It tracks temperatures, amp hours in, amp hours out and other factors. This information is used by the PCM with dozens of other criteria and measurements (like engine torque demand) to determine charging rates - voltages.
As a battery ages, as "cycles" are used the capacity of the battery drops, no longer matching the programming in the PCM. That's where things get goofy. If you can possibly find correct information on batteries out there (good luck!) you'll see that with age and use, batteries lose their amp hour capacity. Heat makes it works, sitting makes it worse, etc. So while the system is told it has a certain battery technology and capacity, as the battery ages and is abused by owners/drivers, things no longer match.
You can help it by:
Separating the negative cables at the IBS to charge the aux battery independently and charge the crank battery independently.
Charge each battery, all by itself, using a proper AGM charger that runs through all of the steps to properly charge an AGM battery.
Charge aux, charge crank battery.
While doing this, have the IBS disconnected, totally off the battery post and unplugged.
Hook everything back up including IBS.
As long as the truck doesn't sit for days, and as long as the drives are at least about 30 minutes, it may be better - however, the actual conditions and age of the batteries will be what determines that.

Always take accessory load grounds from the top of the IBS (a chassis ground stud is perfect for lower capacity loads)
Always charge through the IBS, never charge bypassing the IBS.

 

[ShadowsPapa]

That being said, when auto stop kicks in, the voltage reading on the dash will drop below 12v at times.
Which isn't the case when I read them with the multimeter with the truck off.

You are reading both in parallel.
Batteries will "self recover" to an extent once the load is removed. With the load it may read 12.0 for example and then when the load is removed, it may read 12.4

Since my truck is fairly new, auto stop/start has worked flawlessly since day one, and the battery voltage is always up where it should be with this 2022, I am going to say that the cluster voltage reading is of the aux battery only. There's no way that the crank battery is dropping THAT fast when fully charged just over the load of the electronics.

 

[sharpsicle]

These battery threads are quickly becoming just as bad as oil threads.

I thought this was all pretty well "figured out" already, no? The system's been mapped, the components identified, the functions described, and replacement battery systems successfully implemented. What are we trying to figure out now about batteries, exactly?

If I'm being honest, this thread looks more like a troubleshooting thread than a "let's figure out how the battery system works" thread. If that's the case, then we need to admit that what you're seeing/experiencing could be beyond the scope of just "batteries".

 

[ShadowsPapa]

These battery threads are quickly becoming just as bad as oil threads.

I thought this was all pretty well "figured out" already, no? The system's been mapped, the components identified, the functions described, and replacement battery systems implemented. What are we trying to figure out now about batteries, exactly?

Good question. Very good question. Reinvent the wheel, I guess.
No. it's not "figured out". Much of what you've seen out there is bad or wrong (much, NOT ALL.) (Jerry's diagrams are excellent. It's just that some will try to interpret from those. )
No one has mapped wire sizes/gauges, and there's still a lot of guessing done on loads, draws, voltage drops and so on.

Ironically, even among battery people, there's some disagreement on proper charging of parallel batteries, etc..

The problem is all of the "incorrect" info out there, such as the image of the tech saying a 30 minute charge indicated a bad IBS - add to that the incorrect conclusions -
if this happens, then battery A is bad,
if that happens, then battery B is bad.
Sorry, that's only partially true- under certain conditions.

People want things simple - we can do this in a simple chart.
Need to stop trying to make a very complex system so simple anyone can understand it.
Heck, even many of the "techs" don't get it.
I've been into automotive electric and electronics for decades, I've built automotive solid state voltage regulation circuits, on certain FB pages my name gets mentioned a lot when battery or charging system issues come up and yet I am not even close to having it "all figured out" and I freely admit that.
But people want this simplified so any novice can troubleshoot it for anyone.

 

[mrmo]

I've recently had some battery trouble. I went to the dealer because my Jeep was still under warranty. It took 3 trips to the dealer to resolve the issue. While the dealer worked on my Jeep, I studied the threads here. First impression? Durn, this battery poop is complicated. Even the dealer with all of his fancy tools and training has trouble. Anyway, we should be able to develop a guide/flow chart to help other members here. I'm going to start by listing the possible factors for failure and then sharing my experience.

problems:
Jeep will not start
Stop/Start will not work
Batteries will not charge

components
Main Battery
Aux Battery
Intelligent battery sensor
Fuses
Relays

complicating factors
system parameters (them durn black boxes)
special procedure for jump starts or for charging batteries

easily available info
charging voltage (from the driver's display)
voltage of system before start (from the driver's display, preferably after sitting for the night)

I saved this drawing from my research. I wish I knew who developed this so I could give him/her credit. It's good!

My Stop/Start-Remote Start quit working. I checked the voltage of my batteries before start using both screen 2 on the driver's display and with a multimeter. I also separated the batteries and tested them with my multimeter. My batteries tested at 12.4 volts, i.e., they tested good. Good meaning that the voltage was at an acceptable level for 2.5-year-old batteries.

The first trip to the dealer they tested both batteries, found them good, and replaced the Intelligent Battery Sensor. The Stop/Start worked the first day but quit again on the second day. This was the dealer's comment:

Note that the IBS level the dealer's tech commented on is roughly equal to 12.4 volts form the batteries.

I did not get a report from the second visit. I waited at the dealer while they worked on my car. The Service manager told me that they charged the batteries through the Intelligent Battery Sensor. The Jeep passed the test drive. The Stop/Start worked that day. It would not work after the first night.

My dealer said all the right things and had a good attitude when I called the 3rd time. He asked to keep the Jeep several days and promised to assign a level 3 tech to the job. I gave them the Jeep for a week. This was the report:

They replaced the main battery. The Stop/Start has been working for a week. My conclusion? The Jeep system parameters are set so that a good used battery would not work.

General thoughts form my experience and research?

Stop/Start problems are caused from the main battery.

No start problems are caused by the aux battery.

The Intelligent Battery Sensor is not really intelligent.

The only generalization that is true is that no generalizations are true.

Things I don't understand (not everything ) - Variations of the charging voltage. I've seen 14.7 and 12.8 and everything i
Great drawing I'm gonna use that during my Aux battery elimination project.So as I can afford it, will go w the dual batt
set up

 

[ShadowsPapa]

special procedure for jump starts or for charging batteries

Forgot to add:

There is no special procedure for jump starts - other than connecting to a chassis ground being the safest, and if unwilling to do that, connect to the top of the IBS, not below.
Otherwise, it's jump as usual.

For charging batteries, it's like any other vehicle that uses this system, (including one or two Chevrolet cars - certain Malibu, Impala?), among a number of others (Mercedes, Volvo) - charge through the IBS, not around it.
And - best to separate the batteries. But then this is also not new to most of us who have experience in the field of automotive/truck/industrial equipment -
yes, you can charge batteries while still connected in parallel, but I've usually done it individually. I've had and worked on a lot of equipment over the years with multiple batteries, and I've found it you charge them independently of each other, it's a lot easier to find the culprit if one is bad. Takes more time, but it's a benefit in the end.

Otherwise, I've jump started Jeeps like anything else - connect the cables properly, give the donor vehicle some RPM, wait a minute or two, then start the dead vehicle. Nothing new, nothing different. People get in a big-ass hurry or believe they know - and sometimes it results in failure.

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