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Discussion Starter · #1 ·
Hey folks,

I have a FE ID.4 with 8800 miles on it. This week, I got the car back from the dealer after 4 weeks to perform a battery cell module replacement after the car experienced an electrical system failure, could not drive, and was towed to the dealer on a flatbed. The repair is complete, but I am noticing odd behaviors with the state of charge information. Example:
  • Last night was the first time I charged the car since re-taking possession
  • I charged at home, overnight, with the charge limit set to 80%, which was the readout when I got in the car to go workout this morning
  • I drove about 20 miles total to a park, to coffee with friends, then home.
  • After returning, I plugged the car in at which point the state of charge read 85%
It is quite impossible to have driven the car 20 miles and "gained" 5% state of charge. This is a behavior I noted on CarNet when the car was in the shop--I would get an alert that the ID4 was plugged in with a charge limit set to 80%, and if I checked SoC via Car Net a day after charging had completed, it would be greater than 80%. It seems like something is wrong here. @VW TECHNICIAN is this something you have seen and/or does your experience offer any insight?
 

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21 ProS Red - 23 ProS Plus Arctic Blue locked
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I've seen my SOC percentage jump a point or two during a drive, typically after a charge. I think @VW TECHNICIAN will tell us that the SOC reading is itself an estimate. A battery is not like a gas tank, where you can measure the energy content directly. Unless the battery is at full or empty, the car is guessing the SOC. It's possible that VW sets up its battery guesstimator to give a conservative reading at the start of the drive - I'd rather see the SOC percentage jump a bit during a drive than plummet unexpectedly.

I keep a log of all my charging sessions, where I try to estimate the amount of electricity I've used in-between charges by comparing the reported SOC at the end of my previous charging session to the one at the beginning of the current charging session. When I convert these numbers to miles/kWh, I'm finding that the result does not match the same data reported by the car's infotainment screen. I think there's simply some imprecision here, probably unavoidable when we're dealing with batteries.
 

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2021 AWD Pro S
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I agree with Islander SOC is a guess. It should make a better guess after a few charge/deep discharge cycles so it can learn where 0% and 100% are. Others have reported something similar here.
 

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Agreed, I would bet the system needs to recalibrate, "learn" the new battery voltages it's reading, convert them to % SOC.

The BMS is most accurate at estimating SOC when it is full or empty. Middle state of charge is difficult because the voltage drop is not linear.

If this is bothering you, charge to 100% and then let it run down. Otherwise, just use/charge normally, and it ought to work itself out.
 

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Interesting. The battery monitor on my camping trailer determines SOC by tracking amps going into and out of the battery pack. It compares that to the total amp hour capacity of the battery pack to calculate SOC.
 

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.... The battery monitor on my camping trailer determines SOC by tracking amps going into and out of the battery pack. ...
The ID.4 does this, too ("Coulomb counting"), but uses resting voltage as a double check, and some other tricks I don't understand, to attempt to provide an accurate number. For Coulomb counting to work, it needs a good starting point.
 

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My guess is that the BMS had to relearn how to show the numbers for a healthy pack. Additionally what I see is that after charging when cold, the level rises 2 percent or so when the packs heats up.
So some variation after a short trip can be normal.
 

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Discussion Starter · #8 ·
Thanks for the replies folks. I will be patient and see how it goes. Wife and I ended up doing a drive for some hiking and fall colors and put some miles in and taking the car down to an estimated 34% SoC. I'll see how it responds to the charge overnight.
 

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SOC is not guessing on ID4.
Depending on temperature difference
How long did you wait after charging see SOC
Did BMS finished balancing before you took for drive.
There is multiple sensors that measure required information to calculate SOC.
It has two current sensors to precisely count energy delivered and used.....and there is algorithms that apply to cell voltages....battery temperature......pack resistance ( it will calculate losses and battery health over time).
Every watts is known and if there is drift between internal SOC and infotainment screen it will be 2% between 10-90% and less than 1% from 0-10% and 90-100%.
There could be more differences in some scenarios if battery balancing is needed.
If you have appropriate scanner you will see that internal and infotainment screen SOC greatly differentiate when battery is discharged.......this is because there are a lot of things happening ( temperature rising....resistance is changing....voltage sag under load.....and etc.).
 

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AWD ID.4 Pro S with Gradient package. Dusk Blue with Galaxy Black interior
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I’ve only had my AWD Pro S for about two weeks and have seen this issue also. The dealer charged the vehicle to 100% (not sure how long it sat there at that level), they also left all the tires inflated to 51 PSI vs. 44 PSI.

Anyhow, I’ve charged it once to 90% on my Level 2 charger just before leaving on a 125 mile drive and arrived with 42% (121 miles) left. The place I arrived at didn’t have a level 2 charger so used my level 1 charger for 31 hours to charge to 80%. Then haven’t driven it for 3 days, went out just to sit in it and setup some favorite radio stations and it now shows a charge of 82%.
 

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I’ve only had my AWD Pro S for about two weeks and have seen this issue also. The dealer charged the vehicle to 100% (not sure how long it sat there at that level), they also left all the tires inflated to 51 PSI vs. 44 PSI.

Anyhow, I’ve charged it once to 90% on my Level 2 charger just before leaving on a 125 mile drive and arrived with 42% (121 miles) left. The place I arrived at didn’t have a level 2 charger so used my level 1 charger for 31 hours to charge to 80%. Then haven’t driven it for 3 days, went out just to sit in it and setup some favorite radio stations and it now shows a charge of 82%.
Completely normal....with L1 charger....with just 2+ weeks of ownership and if you follow my posts you will find more how BMS is working and how various other things like temperature and etc. affects SOC .
 

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2021 ID.4 1st Blue - del. 3/16/21 sold 6/4/22
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@VW TECHNICIAN do you happen to know why the SoC displayed by the screen in the car, differs from the SoC that the BMS has in Measuring Values? Is it sort of like a coolant temp gauge that shows "normal" when the coolant is within a fairly wide range, to avoid users freaking out over movements?
 

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@VW TECHNICIAN do you happen to know why the SoC displayed by the screen in the car, differs from the SoC that the BMS has in Measuring Values? Is it sort of like a coolant temp gauge that shows "normal" when the coolant is within a fairly wide range, to avoid users freaking out over movements?
BMS values and infotainment values SOC will be different and if you chart them they will show different SOC ( depending on many factors that involve measuring)
Infotainment screen SOC will be delayed more vs quicker BMS SOC.
This way it will not freak out owners why suddenly SOC is dropping to fast.
There are two current sensors......battery resistance ( that calculate losses and SOH over time)....battery voltages......battery bank's voltage differences......voltage sag....cell temperatures....Battery balancing and etc..... BMS SOC are actual readings at the moment of continuous changes happening non stop.
Where on the other hand infotainment screen SOC are delayed and if there is big drift happening between BMS SOC and infotainment screen SOC (infotainment screen will update).
When charging with L1 or L2 there could be 2-4% between BMS SOC and infotainment SOC.
If battery balancing is needed it will not show true infotainment SOC until passive balancing is finished.
It is quite difficult to explain logic behind.
If you record BMS SOC and infotainment SOC over time while driving you will have better understanding what is happening....and probably better ideas to ask questions.
And I'm quite positive that you have what is needed to see how they interfere between each other.
Good luck.
And for any enthusiasts that want to see under the ID.4 software logic Ross-Tech.com software is the way to go.
I use them as my favorite tool over ODIS.
 

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Thanks for the replies folks. I will be patient and see how it goes. Wife and I ended up doing a drive for some hiking and fall colors and put some miles in and taking the car down to an estimated 34% SoC. I'll see how it responds to the charge overnight.
BMS values and infotainment values SOC will be different and if you chart them they will show different SOC ( depending on many factors that involve measuring)
Infotainment screen SOC will be delayed more vs quicker BMS SOC.
This way it will not freak out owners why suddenly SOC is dropping to fast.
There are two current sensors......battery resistance ( that calculate losses and SOH over time)....battery voltages......battery bank's voltage differences......voltage sag....cell temperatures....Battery balancing and etc..... BMS SOC are actual readings at the moment of continuous changes happening non stop.
Where on the other hand infotainment screen SOC are delayed and if there is big drift happening between BMS SOC and infotainment screen SOC (infotainment screen will update).
When charging with L1 or L2 there could be 2-4% between BMS SOC and infotainment SOC.
If battery balancing is needed it will not show true infotainment SOC until passive balancing is finished.
It is quite difficult to explain logic behind.
If you record BMS SOC and infotainment SOC over time while driving you will have better understanding what is happening....and probably better ideas to ask questions.
And I'm quite positive that you have what is needed to see how they interfere between each other.
Good luck.
And for any enthusiasts that want to see under the ID.4 software logic Ross-Tech.com software is the way to go.
I use them as my favorite tool over ODIS.
My ID4 is also experiencing this same behavior after a having a defective battery module replacement. After the car was returned to me I charged it to 80% and then drove it 1.2 miles, then parked. When I returned hours later the infotainment display showed the SOC to be 89%. I drove the car a few more days and then ran the car down to 30%, again charged back upto 80%, drove 1.2 miles and then parked, within a couple of hours the SOC had increased to 89%.

It makes sense that there can be a difference between the BMS SOC and infotainment SOC due to balancing under the covers. I had not seen this happen before the battery module replacement and the amount of charge it gains seems a tad excessive to me. I would like to know if it is something to be concerned about or is it something that will just eventually recalibrate over time?
 

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2021 FE Mythos Black
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My ID4 is also experiencing this same behavior after a having a defective battery module replacement. After the car was returned to me I charged it to 80% and then drove it 1.2 miles, then parked. When I returned hours later the infotainment display showed the SOC to be 89%. I drove the car a few more days and then ran the car down to 30%, again charged back upto 80%, drove 1.2 miles and then parked, within a couple of hours the SOC had increased to 89%.

It makes sense that there can be a difference between the BMS SOC and infotainment SOC due to balancing under the covers. I had not seen this happen before the battery module replacement and the amount of charge it gains seems a tad excessive to me. I would like to know if it is something to be concerned about or is it something that will just eventually recalibrate over time?
I have never seen an increase in SOC like that.
 

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Discussion Starter · #16 ·
Realized I never gave an update on this. After I went through a charge cycle to 100% for a road trip that also included a deep discharge cycle this behavior went away for me. Perhaps give that a try. After it appeared to "re-learn" (even though I know that isn't really the correct term here) where 100% was, it hasn't been an issue.
 

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My ID4 is also experiencing this same behavior after a having a defective battery module replacement. After the car was returned to me I charged it to 80% and then drove it 1.2 miles, then parked. When I returned hours later the infotainment display showed the SOC to be 89%. I drove the car a few more days and then ran the car down to 30%, again charged back upto 80%, drove 1.2 miles and then parked, within a couple of hours the SOC had increased to 89%. It makes sense that there can be a difference between the BMS SOC and infotainment SOC due to balancing under the covers. I had not seen this happen before the battery module replacement and the amount of charge it gains seems a tad excessive to me. I would like to know if it is something to be concerned about or is it something that will just eventually recalibrate over time?
If you have car scanner app . ...post individual battery cell SOC highest and lowest and highest and lowest battery cell voltage?
 
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