Faulty HV battery pack ?

[pau1ow]

Hi guys,

Just purchased a pre-owned Enyaq IV 80 with over 120k km and was very disappointed to see really high degradation on the 77 kWh pack.
During my first journey (over 700km), i was seeing about 53-55 kWh calculated residual capacity and this was today confirmed when I got CarScanner connected - see below:

As you can see, despite a Maximum Energy Content of 71200Wh, the HV battery energy content is only 34550Wh at 63% SOC, that would mean about 55kWh at 100% SOC (I hate to be right).
The degradation would be about 25% if we consider an original nominal capacity of 73kWh.

What worries me is the high voltage difference between some cells (190mV).

Did anyone have such an issue and got it covered ?

I'm planning to reach out to the Skoda dealer but wanted to get some insights first.

Thanks

[CrowSysE243]

You probably do not need to worry about the failure to display the cell voltage for cells 97 to 108. They are not fitted in an 80. I assume that more would be shown like this on a 60. I believe that they would only be fitted on some of the larger battery (non Skoda) MEB cars. I get the same range of cells shown for my Enyaq.

The large voltage difference is concerning. Generally the voltage difference in mine is about 10mV although it sometimes goes up to 15mV under heavy load. The voltage graphic does seem to show 1 or 2 cells lower than I would expect relative to the others.

I have never had a very good correlation between the battery capacity estimated from the indicated content and the BMS %age and the indicated capacity, At present content/%age is 91% of the indicated maximum capacity and I am getting the expected range, however the same calculation for your data comes out at about 77% which is lower that I have ever seen.

I think it is worth discussing this with Skoda.

[pau1ow]

Thanks for the input I'm reading in other forums (ID4's) that having such a voltage discrepancy (>30mV actually) is really bad and should be called for out of service.
Looks like it's going to the workshop for further analysis.

Edit: what were your values for Maximum Energy Content and HV Energy Content out of interest ? For what mileage and SOC ?

[MacDragon]

Yes, that voltage descrepancy is a notable concern if it doesn't balance or returns immiedietly.

[CrowSysE243]

what were your values for Maximum Energy Content and HV Energy Content out of interest ? For what mileage and SOC ?

The maximum energy content reported was 76200 watt hours. Over the period that I have data for it has varied between 75050 when temperatures have been low for a while, to 78700. The trend has been for it to reduce in the winter and increase in the summer.

The energy content reported was 33975 watt hours with a BMS SoC of 48.8 (Display SoC 47.7) with a battery temperature of 12.5°C, Battery voltage of 355.25 V, estimated range of 157.2 miles and an odometer reading of 24291.3.

These were taken after completing a 50 mile journey.

I have gone back and analysed data taken over 12 months and can see that the percentage calculated from Energy content/Max Energy/BMS SoC has dropped as low as about 60% at low SoC. There are some outliers but generally there is a characteristic curve, shown in the following graph, from about 60% at 13% BMS SoC to about 97% at 96% BMS SoC (~100% Display SoC). The outliers go as high as 182%! The overall average is 93%.

I think that individual data points need to be treated with some caution, particularly without knowing the algorithms used for the estimates and the reliability of the measurements used by the algorithms, but general trends are probably reliable. Basic measurements such as voltage should be fairly reliable, but it is necessary to take into account that the measurements for all cells are unlikely to be taken simultaneously so are most differences are reliable when calculated from measurements taken under stable conditions, however the data that I have suggests that under dynamic conditions there would be a more even spread of voltages with lower overall variation than your measurements show. Under dynamic conditions the data latency can show short term larger Max cell voltage - Min cell voltage variation, with Car Scanner reporting both positive and negative values in quick succession, however the short term average should be within a few 10s of millivolts.

[CrowSysE243]

Most, if not all, or the outliers on the graph are due to stale data and data latency, where the data displayed by Car Scanner for one field has not updated at the time I recoreded it. In some cases these were because I did not have Car Scanner set up to update all the pages of interest when another page was displayed. The 183% result shown at just over 30% charge was due to the Energy Content not having been updated during a 200+ mile drive!

[Aragorn]

Is the car on ME3? That much voltage deviation should be triggering a warning light. My car was triggering the warning light at ~15mv. There was a large recall running for replacing these battery modules due to this exact fault, one cell being degraded.

[pau1ow]

Thanks for chiming in guys.

Yes, I'm on ME3. Which warning light are you refering to ? So far no error code linked to this voltage deviation weirdly.