Battery VCDS data block detailed explanation request?

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Fussybob

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Can anyone explain "in detail" Groups 019 and 020 below. Especially what does Battery Aging (derived from load) and Battery Aging (derived from output) mean?

Also why is Battery Capacity so low at 40Ah with a 91% charge.

Hopefully someone here can explain technically what all this data means for each block.



 
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Uwe

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Unless the person who attempts to explain it has access to documentation for how the control module (in this case a Gateway) calculates those values, I would take any answer(s) you get with a grain of salt. ;)

-Uwe-
 
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Fussybob

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That's why I'm looking for that expert!

I do have a degree in electrical engineering and these numbers make no sense, even with wild guessing.

I have read all the VAG self-study guides for Power Management and unfortunately no info on how this data is obtained or calculated.

Otherwise this data seems meaningless to indicate the possible current life of the battery. The one that really bothers me is the Capacity at such a low level.

Somebody just might know.............
 
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Uwe

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I haven't looked at that particular car, but my experience with a 2005 A6 with separate battery manager module (as opposed to yours that has it integrated in the gateway) is that those kinds of numbers aren't worth much at all -- other than perhaps as a means for the dealer to try to sell you a new battery. ;)

My impression is that guys in white lab coats and fancy "Dr. Dipl. Ing" titles came up with some kind of model regarding the aging performance of a lead acid battery. I think it's based primarily on the amount of energy that gone into and out of the battery, and perhaps the amount of time that it has spent at various SOCs, but IMO the model just doesn't correspond very well to battery performance in the real world.

At one point, Sebastian was looking at the values in the above-mentioned A6 and told me I should replace the battery. I ignored his advice and the car soldiered on for several more years with the original battery -- which incidentally the car thought had been replaced several times early on when we were playing with battery coding, so some of its real-world use wasn't even taken into account.

Anyway, I think that car got 8-1/2 years out of the original battery before I finally had it replaced because I didn't trust it anymore due to age.

OTOH, we've seen batteries fail suddenly for no apparent reason at 2-3 years old too, and I really doubt that Herr Dr. Dipl. Ing's models would predict or warn one of those either.

-Uwe-
 
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DV52

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I haven't looked at that particular car, but my experience with a 2005 A6 with separate battery manager module (as opposed to yours that has it integrated in the gateway) is that those kinds of numbers aren't worth much at all -- other than perhaps as a means for the dealer to try to sell you a new battery. ;)

My impression is that guys in white lab coats and fancy "Dr. Dipl. Ing" titles came up with some kind of model regarding the aging performance of a lead acid battery. I think it's based primarily on the amount of energy that gone into and out of the battery, and perhaps the amount of time that it has spent at various SOCs, but IMO the model just doesn't correspond very well to battery performance in the real world.

At one point, Sebastian was looking at the values in the above-mentioned A6 and told me I should replace the battery. I ignored his advice and the car soldiered on for several more years with the original battery -- which incidentally the car thought had been replaced several times early on when we were playing with battery coding, so some of its real-world use wasn't even taken into account.

Anyway, I think that car got 8-1/2 years out of the original battery before I finally had it replaced because I didn't trust it anymore due to age.

OTOH, we've seen batteries fail suddenly for no apparent reason at 2-3 years old too, and I really doubt that Herr Dr. Dipl. Ing's models would predict or warn one of those either.

-Uwe-

Uwe: Of course I always bow to the superior and awesome knowledge of RT folk, but my understanding (based on my reading of VW's scant literature on this topic) is similar to yours: if the monitoring module is installed, the vehicle keeps a history file of the battery current-in/current-out which is fodder for VW's magic and highly secretive algorithm that then calculates the variables. Again, I will take advice from RT, but on vehicles like the mk7, I believe that it's possible to reset the historic table by changing the battery serial number that is recorded in the CAN Gateway. I've found that the actual serial number entered isn't important - it just needs to be different to the previous entry.

Does fussybob's (love the handle) car have a similar facility - if not, how does the CAN Gateway become aware of a battery change?

Don

PS: Given that the battery history table is built-up over the life of the battery, it seems reasonable to assume that the veracity of the calculated variables is necessarily, very dependent on the owner's practices (as they relate to the battery) - I believe. So, stuff like how an external battery charger, or how the car is jump-started is crucial to the accuracy of the table values. If, for example, the negative lead of an "external power source" is incorrectly connected to the car (i.e. it's connected directly to the negative battery terminal), then it stands to reason that the stored current-in/current-out variables in the table will be wrong (because the battery monitor module is by-passed) -which means that the calculated variables will also be wrong for the life of the battery (I think). Happy to hear from others about this - I'm always willing to learn!!
 
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Uwe

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on vehicles like the mk7, I believe that it's possible to reset the historic table by changing the battery serial number that is recorded in the CAN Gateway. I've found that the actual serial number entered isn't important - it just needs to be different to the previous entry.

Does the 2005 A6 have a similar facility - if not, how does the CAN Gateway become aware of a battery change?
It does. We changed the serial number of the battery quite a few times while working on it early on. It's just in a separate module rather than integrated into in the gateway. Of course, that was a "first generation" battery manager, so it's possible this stuff has improved since then.

PS: Given that the battery history table is built-up over the life of the battery, it seems reasonable to assume that the veracity of the calculated variables is necessarily, very dependent on the owners practices (as they relate to the battery) - I believe. So, stuff like how an external battery charger, or how the car is jump-started is crucial to the accuracy of the table values. If, for example, the negative lead of an "external power source" is incorrectly connected to the car (i.e. it's connected directly to the negative battery terminal), then it stands to reason that the stored current-in/current-out variables in the table will be wrong (because the battery monitor module is by-passed) - I think. Happy to hear from others about this - I'm always willing to learn!!
Agreed. We discovered that very early on with that A6 when we connected a charger directly to the battery while we were doing our normal development/testing. It's not unusual for our cars to spend hundreds of hours with key on, engine off, while connected to "shore power". Anyway, that silly A6 started shedding loads despite having shore power keeping the voltage at appropriate levels, because thought that the current it saw powering the car was coming from the battery rather than the charger connected to the battery. I commented back then I thought it was pretty stupid of the battery manager to do this when there was no voltage drop that corresponded to the amp-hours it thought were being drawn from the battery.

-Uwe-
 
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Fussybob

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I haven't looked at that particular car, but my experience with a 2005 A6 with separate battery manager module (as opposed to yours that has it integrated in the gateway) is that those kinds of numbers aren't worth much at all -- other than perhaps as a means for the dealer to try to sell you a new battery. ;)

My impression is that guys in white lab coats and fancy "Dr. Dipl. Ing" titles came up with some kind of model regarding the aging performance of a lead acid battery. I think it's based primarily on the amount of energy that gone into and out of the battery, and perhaps the amount of time that it has spent at various SOCs, but IMO the model just doesn't correspond very well to battery performance in the real world.

At one point, Sebastian was looking at the values in the above-mentioned A6 and told me I should replace the battery. I ignored his advice and the car soldiered on for several more years with the original battery -- which incidentally the car thought had been replaced several times early on when we were playing with battery coding, so some of its real-world use wasn't even taken into account.

Anyway, I think that car got 8-1/2 years out of the original battery before I finally had it replaced because I didn't trust it anymore due to age.

OTOH, we've seen batteries fail suddenly for no apparent reason at 2-3 years old too, and I really doubt that Herr Dr. Dipl. Ing's models would predict or warn one of those either.

-Uwe-
I agree with you that this data has no real merit, that is why I was looking for the holy grail explanation if one exists.
 
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Fussybob

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Uwe: Of course I always bow to the superior and awesome knowledge of RT folk, but my understanding (based on my reading of VW's scant literature on this topic) is similar to yours: if the monitoring module is installed, the vehicle keeps a history file of the battery current-in/current-out which is fodder for VW's magic and highly secretive algorithm that then calculates the variables. Again, I will take advice from RT, but on vehicles like the mk7, I believe that it's possible to reset the historic table by changing the battery serial number that is recorded in the CAN Gateway. I've found that the actual serial number entered isn't important - it just needs to be different to the previous entry.

Does fussybob's (love the handle) car have a similar facility - if not, how does the CAN Gateway become aware of a battery change?

Don

PS: Given that the battery history table is built-up over the life of the battery, it seems reasonable to assume that the veracity of the calculated variables is necessarily, very dependent on the owner's practices (as they relate to the battery) - I believe. So, stuff like how an external battery charger, or how the car is jump-started is crucial to the accuracy of the table values. If, for example, the negative lead of an "external power source" is incorrectly connected to the car (i.e. it's connected directly to the negative battery terminal), then it stands to reason that the stored current-in/current-out variables in the table will be wrong (because the battery monitor module is by-passed) -which means that the calculated variables will also be wrong for the life of the battery (I think). Happy to hear from others about this - I'm always willing to learn!!
Yes you need to change at least 1 digit in the serial number to reset the battery history table with a new battery change.

Some Power Management info below. Guess we need the engineer that developed this to explain the complexity.

History data......

The diagnosis tester can be used to read out
data from the control unit for power management,
which makes it much easier to analyse the on-board
power supply and the battery.

Open-circuit voltage history

If the battery open-circuit voltage is less than the
threshold values of 12.5 volts, 12.2 volts and
11.5 volts, an entry is written to the history data.
The last four entries can always be read out.
Voltage measurement starts when
– CAN Convenience is in Sleep mode and
– terminal 15 is switched off for at least 2 hours
and
– the vehicle’s power consumption is < 100 mA.
Voltage measurement ends when
– the voltage increases or
– the current increases or
– the control unit triggers Sleep mode or
– the control unit detects a new battery.

Closed-circuit current history

If the closed-circuit current exceeds the threshold
value of 50 mA, an entry is written to the history
data. The last ten entries can be read out.

Current measurement starts when

– CAN Convenience is in Sleep mode and
– terminal 15 is switched off for at least 2 hours
and
– the vehicle’s power consumption is > 50 mA.
Current measurement ends when
– the current decreases or
– the control unit triggers Sleep mode.

Breakdown analysis

If the control unit for power management detects
the status "Cannot start vehicle", an entry is written
to the history data.


Battery change

Data for the last three battery changes is stored.
Power balance history – driving (= engine on)
The power balance and duration of the last five
journeys are logged.
Power balance history – idle (= engine off)
The power balance and duration of the last five idle
times are logged.
Other data is not relevant for Customer Service
 
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DV52

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I agree with you that this data has no real merit, that is why I was looking for the holy grail explanation if one exists.
bob: I'm not entirely sure that Uwe was saying this!

I'm certainly not an expert on these matters, but from what I have read, most (all?) of the calculated variables are used by the control modules as input data for their decision making. For example, I believe that a calculated voltage (based on battery voltage, but different to battery voltage) is used by the Start Stop facility in my mk7 for deciding whether there is sufficient charge in the battery to restart the engine after it is stopped by the control module. Whilst I agree that some of the variables appear to be somewhat arcane, I would guess that they are all required by the vehicle!! It's just that we don't know that reason because such little information is in the public domain!!

Don
 
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The aging values are primarily derived from the internal resistance of the battery, that said other factors will come into play - hence the 2 different results (load & output). From a typical diagnostic point of view (in terms of do you need to replace that battery or not), what you really ought to look at is MVB 022 and in particular the 'Total Energy Throughput' as it gives you an idea how much that battery has provided over time and with the proper rule of thumb you get a very good idea if that battery is on it's last breath or not. Mind you, these values are being reset once you code a new battery - so assuming that has been done properly (if the battery has been replaced in the past) the values should be pretty accurate. That said, if hasn't been done properly, a new battery will not work right as the battery management will use the aging information etc. from the old battery to ensure the car is powered accordingly and that may or may not result in odd readings as well as occasionally an incorrectly charged new battery which will then fail. Back to the throughput though...

So let's say your reading 5341 Ah as total energy throughput and you got a 110 Ah battery installed. The rule of thumb is 50 times battery capacity is how much a battery will usually be able to deliver under normal conditions. So we're talking 5500 Ah with a 110 Ah battery. Looking at a possible 5341 Ah reading, gives you a good idea that the battery is either close to it's end of life or already there.

Per my experience, the battery management data ís highly undervalued and often misread - but hey, just my 2 cents. ;)
 
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Uwe

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So let's say your reading 5341 Ah as total energy throughput and you got a 110 Ah battery installed. The rule of thumb is 50 times battery capacity is how much a battery will usually be able to deliver under normal conditions. So we're talking 5500 Ah with a 110 Ah battery. Looking at a possible 5341 Ah reading, gives you a good idea that the battery is either close to it's end of life or already there.
50x rated capacity would be 500 cycles at 10% depth-of-discharge, or 250 cycles at 20% depth-of-discharge. This strikes me as *extremely* conservative, even for a starter battery.



-Uwe-
 
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The aging values are primarily derived from the internal resistance of the battery, that said other factors will come into play - hence the 2 different results (load & output). From a typical diagnostic point of view (in terms of do you need to replace that battery or not), what you really ought to look at is MVB 022 and in particular the 'Total Energy Throughput' as it gives you an idea how much that battery has provided over time and with the proper rule of thumb you get a very good idea if that battery is on it's last breath or not. Mind you, these values are being reset once you code a new battery - so assuming that has been done properly (if the battery has been replaced in the past) the values should be pretty accurate. That said, if hasn't been done properly, a new battery will not work right as the battery management will use the aging information etc. from the old battery to ensure the car is powered accordingly and that may or may not result in odd readings as well as occasionally an incorrectly charged new battery which will then fail. Back to the throughput though...

So let's say your reading 5341 Ah as total energy throughput and you got a 110 Ah battery installed. The rule of thumb is 50 times battery capacity is how much a battery will usually be able to deliver under normal conditions. So we're talking 5500 Ah with a 110 Ah battery. Looking at a possible 5341 Ah reading, gives you a good idea that the battery is either close to it's end of life or already there.

Per my experience, the battery management data ís highly undervalued and often misread - but hey, just my 2 cents. ;)
Sebastian,

Thanks for the reply. Looks like we need the VAG engineering group responsible for Power Management to explain all calculations, which we most likely will never know.

Battery internal resistance is based upon so many different variables, plus the vehicles Power Management history log data is most likely used for the calculations that anymore guessing is not worth it.

Now MVB 022 is more to my liking, I wasn't aware of what this data meant.

I read my Q5 data today and it indicates Total Energy Throughput of 1489 Ah, I have a 110 Ah battery so 50 X battery capacity rule of 5500 Ah should relate that I used 30% of my battery life.
This is interesting as the Battery State as shown in the MMI is 70% and Battery Aging (derived from load) is also 70% so maybe they just correlate. I will watch all these data points over
time to see if the correlation continues.

Now with my data gathering today of MVB 022 there is a data block called Total Energy Balance (9716 Ah) do you know what this is?
 
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Jack@European_Parts

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I think it's safe to say....... Bruce and Uwe know their battery and power conversion stuff........:p
 
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The above mentioned rule of thumb was originally brought during Audi technician training courses and after having used it for the last 10+ years - it has rarely failed. Obviously I am not an expert at this, merely trying to give an easy to use and hands on approach on this subject from a typical service/maintenance point of view.
 
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These sites listed below clear up a lot of the mysteries of the measuring block data.

I spent all day yesterday reading about batteries and charging/discharging and learned a lot!

http://batteryuniversity.com/learn/

http://www.mpoweruk.com/bms.htm



Read the SU600 and Su900 series articles in the Battery University.

The BMS articles also sheds light on what the vehicle Power Management system is doing to calculate the end result data.

Bottom line, it looks as though there is an energy measuring sensor at the battery used as a coulomb (energy) counter. By monitoring the battery open circuit voltage rise and fall,
and the corresponding amount of coulombs going in and out of the battery during charging/discharging, the charging time decreases as the battery ages and the capacity is reduced. The amount of
monitored coulombs going in also decreases during the charge up. Comparing this data to the stored Power Management History data results in a battery aging percentage that is usable but not exactly accurate.

I'm not sure when the Audi battery is coded into the system what information is provided by the battery part number and serial number that the Power Management system uses. Looking at a Varta BER code it corresponds to battery size, capacity, and CCA. The capacity number is obviously used. The internal resistance can be calculated when a new battery is installed and used as the reference baseline for future comparisons.

I now have a better understanding of the Power Management data, resulting calculations, and the present VCDS Measuring Block data.
 
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Per my experience, the battery management data ís highly undervalued and often misread - but hey, just my 2 cents. ;)
If you read the SSPs, some sophisticated work was obviously done by the designers of the Battery Manager ECU that's in various A8s and A6s [among others]. However, it seems it was to no avail since to diagnose issues with it or the charging circuit you need :

a) The data from the ECU [which keeps at least 3 battery code's worth] - which I believe is only read by the VAG VAS5xxx. [I asked for this in VCDS previously but not much interest shown].
b) Some understanding of what the data shows - which only a small subset of the users capable of accessing the data in a) are themselves seemingly capable of. :(

I've had various 'battery going flat' problems with my A8 over the years and I'm trying to diagnose one as I type; I'm actually suspicious my Battery Manager ECU isn't working properly as I NEVER get any displays or warnings in the Instrument Panel Display [DIS], even when the battery goes almost flat. :banghead:

But having looked at both A8 and A6 salvaged ECUs on sale in UK eBay, there are at least 8 variations [hardware/software levels] of both of these ECUs and that seems to suggest to me that at least 7 of each weren't quite right! It's really irritating that you can't find out what changes were made at each revision level.:mad:

======================================================================
Just for info; the following ECUs seem to be the 'last' of each, implying they finally got it right!

A8 - HW 4E0 915 181C - SW 4E0 910 181C - H12 0550
A6 - HW 4F0 915 181B - SW 4F0 910 181F - H12 0760

[I've got an A8 one @ H11 0510 [which seems quite a rare level]]
======================================================================

Julian

By the way Ross Tech; I still think you'd make a lot of people happy [and solve some frustrating 'going flat' problems] if you could add functionality to VCDS to read the Battery Manager Logs and data.
 
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Uwe

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By the way Ross Tech; I still think you'd make a lot of people happy [and solve some frustrating 'going flat' problems] if you could add functionality to VCDS to read the Battery Manager Logs and data.
At this point, that is actually a work-in-progress.

-Uwe-
 
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At this point, that is actually a work-in-progress.

-Uwe-
That's really good news :thanks:

And I've got an A8 D3 I'd love to test it on ... ;)

Julian
 
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That's really good news :thanks:

And I've got an A8 D3 I'd love to test it on ... ;)

Julian
Me too, especially as the fairly new biggest baddest AGM that i could fit in her went flat overnight to the point of not being able to open the mmi screen let alone start it. :banghead:
 
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