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BQ20Z95: Negative values in Ra table

Helge Larsen
Prodigy 20 points

Part Number: BQ20Z95

We have got returned batteries from customer complaining over batteries reporting empty after few cycles. Reading battery status using "bq Evaluation Software" we can see and measure that the battery capacity and cell voltages are fine, however even with 100% charged, Abs state of charge report 0 and RemainCharge Alarm (which we use in our device to activate safe power-down) is set.

Unlocking the battery and looking into DF shows every setup correct and identical to Golden Device. However - the updated Ra-table shows strange negative values for two of the four cells (4s3p config). for two celles - all gridpoints shows -32767 . All cells Qmax seems reasonable (6800 to 7000mAh) with Qmax-pack identical to the lowest cell. 

We have tried charging - relaxing (day) decharging - relaxing again - see no update of the Ra values for any of the four cells at all !

What is wrong - what shall we do ?

  We have produced this battery for almost 10 years - newer seen problems like this before

BR Helge Larsen

  • 0
    TI__Mastermind 25955 points
    Hi Helge,

    Please send us a copy of the gg file for further analysis and follow these steps.

    0. Export GG file for later comparison.
    1. Set the strange negative RA values back to reasonable values (copy from either a better cell, or another table).
    2. Send Reset command (0x0041)
    3. Charge the pack to charge termination.
    4. Rest until the VOK flag sets
    5. C/7 Discharge to the termination voltage
    6. Rest until the VOK flag sets.
    7. Charge the pack to charge termination
    8. Rest until VOK flag sets
    9. C/7 Discharge to the termination voltage
    10. Rest until the VOK flag sets. At this point, the Ra table should update.
    11. Export the GG file and diff against the GG file exported in step 0. Check to see if RA values have now updated.

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    TI__Mastermind 25955 points
    Hi Helge,

    I hope these steps helped out. If your issue still persists, please let us know and send the gg.csv files and logs from the gauge for further analysis.

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    Prodigy 20 points

    Negative Ra.zipHi Bryan

    Sorry for late respond.

    I thought I had send  the gg-file, obvious something vent wrong. Now trying again - now zipped version including a gg file from the bad battery (named DCNS)  and one from a new production unit (ref.gg) . Also included charge/discharrge log from the failing battery.

    I tried your 11 steps  menu - without success. It turns out that VOK never sets - and not only the negative Ra values remain - all Ra values seems to be frozen.

    It looks as the internal communication necessary for updating flash memory  don't work. Could may be a simple defect component - I was told that customer have more batteries like this, however I not sure this hold.

    If you don't have a clue, maybe we should categorize this as an simple  component defect  - whats your opinion?

    BR

    Helge Larsen

  • 0 in reply to Helge Larsen
    TI__Mastermind 25955 points
    Hi Helge,

    It will definitely require some investigation. If the returns are low and you believe they aren't worth the time spent investigating, we can table the issue. If not, please let me know and we can work on it on both ends.

    Sincerely,
    Bryan Kahler