Your battery voltage - truck off and at rest

[Andy29847]

multiple post

Thank you for sharing your work.

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[ShadowsPapa]

@ShadowsPapa , thanks for all the testing, especially your explanation of the steering induced voltage fluctuation during an ESS stop.

Regarding the draw on the crank battery during an ESS stop, I expect that the crank battery is powering all the engine electronics like the fuel pump, injectors and under hood electronics. My diagrams are based on what was included on the charging circuit schematic and does not include information from other circuits.

I don't feel like tearing off my PDC to trace all of those, LOL
I did do a full charge today, and made up a second lead so I can quickly switch my meter between crank and aux battery without getting out into 15 degree weather but more testing will take time since it's the weekend and all.

Me being me - I'm curious as heck on things like this. My grandfather used to bring me things from the city dump - lawn mowers, radios, TVs, etc. - so I could tear into them and see what was inside.
And I hate it when I am not sure of something - bugs the heck out of me.

I can tell you that almost everything is on N1.
.......... cluster, center stack/switches, radio, BCM, PCM, ABS, HVAC, fuel pump, fuel pump control circuit and relay, trailer tow (thus no ESS stop if towing), horn, heated back glass, front facing camera heat (for ACC, FCW), ABS, sway bar module, steering column sensors and controls.........

N2 or the crank battery is fans, EHPS pump, and starter but little else.

 

[jebiruph]

I don't feel like tearing off my PDC to trace all of those, LOL
I did do a full charge today, and made up a second lead so I can quickly switch my meter between crank and aux battery without getting out into 15 degree weather but more testing will take time since it's the weekend and all.

Me being me - I'm curious as heck on things like this. My grandfather used to bring me things from the city dump - lawn mowers, radios, TVs, etc. - so I could tear into them and see what was inside.
And I hate it when I am not sure of something - bugs the heck out of me.

I can tell you that almost everything is on N1.
.......... cluster, center stack/switches, radio, BCM, PCM, ABS, HVAC, fuel pump, fuel pump control circuit and relay, trailer tow (thus no ESS stop if towing), horn, heated back glass, front facing camera heat (for ACC, FCW), ABS, sway bar module, steering column sensors and controls.........

N2 or the crank battery is fans, EHPS pump, and starter but little else.

There's a conflict with the schematics I'm finding on the forums, starting_charging shows the PCM powered from N2 (crank) and fuses---battery shows the PCM powered from N1 (aux). I'm not finding anything for things like injectors and coils.

Do you have a different source or are you looking at what's available online?

 

[ShadowsPapa]

There's a conflict with the schematics I'm finding on the forums, starting_charging shows the PCM powered from N2 (crank) and fuses---battery shows the PCM powered from N1 (aux). I'm not finding anything for things like injectors and coils.

Do you have a different source or are you looking at what's available online?

To me, it's not showing the PCM itself but the modules and relays it controls coming from N2
For example - the power for the PCR relay (the relay that CONTROLS the PCR) comes from N2 but the same relay's contacts power comes from N1 so the PCR itself is opened by power from N1, but the relay that sends power to the PCR's coil comes from N2.

So the PCR will have some things coming from each as far as the things it controls but the power for the PCR itself to operate.............

There's power going to the PCM from both, the PCM (and I've not had time to go over all 4,000 documents) itself seems to be N1. The circuits it controls such as start, and so on, N2, injectors - N1.
Like I mentioned for the PCR - the relay that controls the relay comes from N2, the crank battery but the PCR itself is part of N1. It's a PCM switching circuit controlling a relay on the PCB of the PDC which controls the bigger relay.
It sort of makes sense they'd split things out a bit for the control, but the actual functions for "electronics" comes from N1.
That's what I've seen so far.

 

[ShadowsPapa]

Interesting drive today -
Preface it with this: the temps were 18 down to 16 during the drive time so that may be "the" factor if not a big one.
Yesterday I connected my AGM charger and set it to the 10 amp setting.
When it came on, it said the battery was 12.6 volts, 80-some percent charged. Interesting since I'd not driven it much other than the voltage checks I had done earlier. Prior to that, it had been sitting.
I let the charger run and it was done by later afternoon but I left it connected to see if it would go into maintenance mode.
This am I went out and the charger was full off, 100% charged, 12.8 volts.
I disconnected it about 1pm
We took it to church today - a 30 minute drive. For almost the entire time, once again it was showing 15.0 volts, and after a few miles and when the speed limit dropped, it settled on 14.9 volts.
25 miles/35 minutes later, shut it off, then came back out 45 minutes later and drove it back home.
The whole time it was at 14.9 volts.
Now consider that was cold - but still, a fully charged battery that was indeed topped to 12.7 volts.
We're in for a long deep cold spell here so I won't have much more info for weeks if not months, but I'm curious as heck now. My other JT never sat at voltages that high, battery full or not full, it just didn't. This routinely runs a lot higher voltage and especially when it's cold out.
Since I charged correctly through the IBS (and the batteries started out with 12.7 volts) I assumed it would see the battery as fully charged and once the engine bay was warmed up a bit - especially after sitting a while in a parking lot - it might back off a bit.

 

[jebiruph]

Interesting drive today -
Preface it with this: the temps were 18 down to 16 during the drive time so that may be "the" factor if not a big one.
Yesterday I connected my AGM charger and set it to the 10 amp setting.
When it came on, it said the battery was 12.6 volts, 80-some percent charged. Interesting since I'd not driven it much other than the voltage checks I had done earlier. Prior to that, it had been sitting.
I let the charger run and it was done by later afternoon but I left it connected to see if it would go into maintenance mode.
This am I went out and the charger was full off, 100% charged, 12.8 volts.
I disconnected it about 1pm
We took it to church today - a 30 minute drive. For almost the entire time, once again it was showing 15.0 volts, and after a few miles and when the speed limit dropped, it settled on 14.9 volts.
25 miles/35 minutes later, shut it off, then came back out 45 minutes later and drove it back home.
The whole time it was at 14.9 volts.
Now consider that was cold - but still, a fully charged battery that was indeed topped to 12.7 volts.
We're in for a long deep cold spell here so I won't have much more info for weeks if not months, but I'm curious as heck now. My other JT never sat at voltages that high, battery full or not full, it just didn't. This routinely runs a lot higher voltage and especially when it's cold out.
Since I charged correctly through the IBS (and the batteries started out with 12.7 volts) I assumed it would see the battery as fully charged and once the engine bay was warmed up a bit - especially after sitting a while in a parking lot - it might back off a bit.

Must be a programing change. My JL charged in the mid 14v for years, but never went over 14.8v. I wonder if they still put the 14.4v charging limit warning on the aux battery.

 

[Vtur]

When my ESS battery was going out, it was constantly charging above 14v. It's now fluctuating between 12.5-14.8 after battery replaced.

 

[ShadowsPapa]

Must be a programing change. My JL charged in the mid 14v for years, but never went over 14.8v. I wonder if they still put the 14.4v charging limit warning on the aux battery.

I've noted that 14.4 on several batteries, even non-MOPAR and sort of laughed. Even a good AGM charger exceeds that. At least mine do. And my 2020 wasn't afraid to hit 14.6-14.7 at times.

Once the weather changes, maybe if things warm up, I'll get a chance to do more testing. Nice having wires run into the cab to easily check each independently from in the cab.
I keep forgetting - no need to talk weather to you! You're living it, too.

When my ESS battery was going out, it was constantly charging above 14v. It's now fluctuating between 12.5-14.8 after battery replaced.

Mine has done this since new - well, it's only recently been above 14.7-14.8 but that's likely the temperatures. Batteries are harder to charge when cold. Chemical reactions slow greatly. Even in the 1960s voltage regulators were temperature compensated - nothing new at all - and these take the temp from the IBS right at the battery. In years past, it was a reason to have an external regulator close to the battery. Somewhere I have the charts from Motorola, GM, etc. on the difference regulated voltage at various temperatures.

My 2020 was normally in the range 14.6 (sometimes more) down to 12.6 when it was HOT out on a long drive. The latter is to keep from over-heating the battery. If the IBS says it's close to SoC and the temperature is above a certain point - it cuts charging off and simply maintains voltage, no charging.
Can't wait for spring, now! I am anxious to see if what I'm seeing is totally or nearly totally temperature related.
We're talking another drive down to FL, maybe even LA to see the swamps, so there may be chances to get it on a looong drive in 2023.

 

[sarguy1941]

So i'll be honest and say I didnt' read all 20 pages so I may of missed the answer. I noticed recently when my ESS activates at a light and the truck restarts all my radios shut off and back on when the truck starts. All B+ is run to the main battery, with ignition sense for power. I have not tested DC power yet but assume my main battery is lacking ? I thought the ESS battery was for starting only ? Seems odd. For reference 2020. Just started recently.

 

[Mr._Bill]

So i'll be honest and say I didnt' read all 20 pages so I may of missed the answer. I noticed recently when my ESS activates at a light and the truck restarts all my radios shut off and back on when the truck starts. All B+ is run to the main battery, with ignition sense for power. I have not tested DC power yet but assume my main battery is lacking ? I thought the ESS battery was for starting only ? Seems odd. For reference 2020. Just started recently.

The ESS battery is to keep the computers stable during ESS events. The electronics run off of it while the engine is off. Both batteries need charged and tested. The AGM batteries typically last about three years in these trucks. Cold weather and driving patterns are factors in battery behavior. If it is getting driven at least thirty minutes every day, I would suggest just replacing both batteries. If not, then separately charging each battery will probably fix it for a while.

 

[Maximus Gladius]

Looks to me like none of these are ever getting a full charge! That leads to really short battery life in the long run (or short run in this case)
Looks like the vehicle isn't even fully charging the battery to begin with, and then it's dropping 20% or more of it's charge sitting 2+ hours?
That's crazy.

(A little back story to explain how my same factory batteries are today)
Do you remember back a year or so when I was going through that nightmare with my first grenaded transmission and the first dealership had it on their lot while I was engaged in a big fight with them, FCA and AMSOIL? They finally ended up telling me to get it towed back home or pay for the tranny replacement.

I arranged for the tow and told the dealership to make sure the engine could run so I have brakes and steering when the tow truck delivers it to my garage. “For sure” they said.

Tow truck is lowering my truck off his ramp on a difficult angle to my garage and ….truck wouldn’t start, in fact the wipers were glitchy moving across the windshield. The cab lights and signal lights were strobing etc. The dealership gave it back dead and told me to fix it myself, they didn’t want it back. It was dead of winter, -30c and that’s how they gave it to me.

Truck would then sit in the garage for another 7.5 months. For the longest time I wasn’t touching my batteries. It wasn’t my responsibility to fix that. But then I got extremely bored and took out both batteries and put them on a trickle charger. (It was the wrong kind, not an AGM charger) I didn’t realize they had to not be lithium so I did get an AGM trickle charger and would repeatability charge both batteries to full, then watch the V drop. Over a course of a lot of time, the batteries got better and better and they would hold their charges higher, for longer.

Race ahead a bunch of months and tranny gets replaced, I mention the batteries to the new dealership and they put them on their charger checker and say these batteries are solid, no problems.

So here we are today (48k kms) with the same batteries and an 1.5A AGM trickle charger installed and from time to time I’ll charge it through the night and in the morning the batteries will read 12.8 - 13V and I’ll drive off to work which is all over Calgary and the ESS won’t work, dash says Start/Stop not ready.

By the time I get home, V’s have dropped to around 12.5/6 and by morning will be 12.45 and the ESS will work fine. When I get back in for the night, will charge them back up to 13V and the whole thing repeats.

This time, I’ve let the v drop to 12.45v to see it just wants to stay there. My charge system in the trucks says 14v+ all day so I can’t understand why the batteries never reach full charge. The ESS won’t work when they are full so when the Engine does stop, I know the batteries have discharged to around 12.5v or so and dropping.

This morning, checked the batteries and the read 12.3v so I plugged in the charger.

Truck goes in on Tuesday for a bunch of stuff and I’ll mention the batteries and if nothing is done, I’ll pull the F42 fuse and pull the ground wire on the Aux and see if the main keeps dropping.

So, my batteries have been to hell and back from being run down to dead, then frozen, then dormant for months, then cycled many times with the wrong charger, then the right one was used and they just work now except for a small discharge it seems.

 

[sarguy1941]

The ESS battery is to keep the computers stable during ESS events. The electronics run off of it while the engine is off. Both batteries need charged and tested. The AGM batteries typically last about three years in these trucks. Cold weather and driving patterns are factors in battery behavior. If it is getting driven at least thirty minutes every day, I would suggest just replacing both batteries. If not, then separately charging each battery will probably fix it for a while.

It's driven a few times a week. I suspect it's the batteries. I normally throw an optima in all my trucks but wait until the factory is done. Guess I'll order one for the main.

 

[ShadowsPapa]

Race ahead a bunch of months and tranny gets replaced, I mention the batteries to the new dealership and they put them on their charger checker and say these batteries are solid, no problems.

So here we are today (48k kms) with the same batteries and an 1.5A AGM trickle charger installed and from time to time I’ll charge it through the night and in the morning the batteries will read 12.8 - 13V and I’ll drive off to work which is all over Calgary and the ESS won’t work, dash says Start/Stop not ready.

By the time I get home, V’s have dropped to around 12.5/6 and by morning will be 12.45 and the ESS will work fine. When I get back in for the night, will charge them back up to 13V and the whole thing repeats.

This time, I’ve let the v drop to 12.45v to see it just wants to stay there. My charge system in the trucks says 14v+ all day so I can’t understand why the batteries never reach full charge. The ESS won’t work when they are full so when the Engine does stop, I know the batteries have discharged to around 12.5v or so and dropping.

This morning, checked the batteries and the read 12.3v so I plugged in the charger.

Totally freaky on the voltage pattern and ESS.
Mine works with a full charge, and works down to roughly 12.4. At least that was on the 2020.
The 2022 is a bit different in that it seems to work at slightly lower charges.
There's absolutely been changes to the "programming" on these as far as voltages.
My running voltage is 14.9-15.0 if the temps are below about 35 (haven't caught it exactly because our temperatures vary wildly from hour to hour and day to day and the garage is often a lot colder on a warm day due to it taking a while to warm up - it's not insulated but holds the heat or cold for a day, usually)
But yesterday, it was 40 and I noticed the running voltage was only 14.6 for any of our drives (and WEIRD as heck, the ambient temp sensor was working perfectly as well - it was 40 out and the temp on the dash said it was 40)
Anyway, I use JSCAN to change the TPMS settings since stock tires on Overland should be 38 and the tires I have should be 36 so the thing was kicking a fit when the cold hit. Jscan only goes in 5 psi increments this release so I was stuck choosing 35.
I did a BCM dump for kicks (their logs suck compared to AlfaOBD but whatever).
The cluster said 12.1 volts- Jscan said:
Intelligent Battery Sensor Measured Voltage;12/31/2022;11:51:19:59;12.1199998855591
Well, whaddyaknow. A match.
Of course that was with 2 button pushes into run mode so of course more load means that 12.1199 etc. is lower than if there wasn't any drain on the batteries.
Holy cow - is this correct? The big button pressed two times to put it in RUN mode with engine not running and this would seem to be a pretty healthy drain while I'm sitting fiddling around with settings and logs -
Intelligent Battery Sensor Current;12/31/2022;11:51:18:66;-8.31999969482422

So assume it was really 12.3 - 12.4 (wild guess( with no draw - which fits this from jscan:
Intelligent Battery Sensor State of Charge;12/31/2022;11:51:21:01;65

We drove it a few hours after I set the TPMS and did this logging and the ESS worked after only about a mile or so.
The ESS also worked after I did a full charge with a 20 amp charger over several hours time several days ago.

It seems to me that when the temperatures outside are cold - sub-30s, these batteries take a lot to charge, and yet - running 14.9-15.0 volts should more than do the trick.
But then - voltage does not mean high amperage into the batteries - battery resistance controls that. I know back when I got into auto electric and charging systems years ago, a battery presented a load, a resistance, and if the battery was bad, for example, low, open, shorted, whatever, you couldn't check anything else.
This is another thing that is measured by these systems:
Intelligent Battery Sensor Calculated Battery Resistance;12/31/2022;11:51:18:53;3.59999990463257

I'm off my rocker, of course, but add in the resistance of the IBS itself and you have less than 4.5 amps.
Naw, need coffee, that can't possibly be how it works...... ok, gotta think this through...........

Intelligent Battery Sensor Resistance at 100% SOC and 25 DegC;12/31/2022;11:51:21:94;3.09999990463257

I plan on going out - with no FOB to trigger any lights or anything, and measure the voltage at the batteries as it sits now. It's cold out, yes, but we did drive it last evening and it was parked at about 5:30pm after the system voltage sat at 14.6 for the whole 30 minute drive home.

I noticed recently when my ESS activates at a light and the truck restarts all my radios shut off and back on when the truck starts. All B+ is run to the main battery, with ignition sense for power. I have not tested DC power yet but assume my main battery is lacking ? I thought the ESS battery was for starting only ? Seems odd. For reference 2020. Just started recently.

Mr._Bill is a smart guy and has been around the block a few times on batteries and electric.
Like he said - Aux battery runs the "electronics"
Main battery runs EHPS (power steering pump) and radiator fans directly. I haven't taken a PDC apart to see what else might be run from the main battery, but suffice it to say, when mine with 100% fully charged batteries is at an ESS stop, I can monitor both the aux battery and the crank battery independently and that crank battery voltage drops pretty quickly as well at an ESS stop.
If I ever get a change I want to take the PDC from a totaled Gladiator and map it out circuit by circuit like I've done with older Jeeps from the 90s.
Do make very sure that any time you add accessories that require a ground, you use one of the chassis ground studs or the stud on TOP of the IBS. Never ground to the battery terminal below the IBS.
The IBS needs to track everything in and out (although ironically, it can't do that for the aux battery which IMO is sort of dumb)

Intelligent Battery Sensor Lifetime Charge Received;12/31/2022;11:51:19:17;937.869995117188

Intelligent Battery Sensor Lifetime Charge Released;12/31/2022;11:51:19:31;923.25

You might think that with more received than released, my battery would be over 100% charged.... but really that's pretty close because batteries lose charge just sitting even with no "drain" on them.

 

[J Sierra]

8 1/2 digit voltmeter cost $10,000, there is not one in you Jeep. 12.1199998855591 not a real measurement

 

[ShadowsPapa]

So a 60K truck with all of the electronics and networking inside can't measure voltage past tenths or hundredths.
Granted, the numbers likely only go out to the thousandths, same for the resistances because the last 12 numerals are the same for both IBS and battery resistances.
All I did was post exactly what the logs said - I didn't say "this is 100% accurate down to the billionth of a volt."
I just copied and pasted the log entries.
We don't care out past hundredths. The point was the cluster was showing 12.1, the logs showed 12.11x and the cluster DOES round, although it follows some interesting rounding rules.
Very likely the final digits have meaning only to FCA's equipment.

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