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BQ40Z50: BQ4050 RSOC not change when RM is 0mAh

Star Xu
Genius 9645 points
Part Number: BQ40Z50

Hi

The customer design with BQ40Z50, the problem is after the remaining capacity is updated to 0, the SOC has not changed to 0. Wait about 10 seconds then the SOC is updated to 0.

Attached the data.

The reason why Remaining Capacity is updated to 0 (Term Min Cell V), but I don’t know why SOC is not updated to 0 synchronously.

Waiting for your reply.

Thanks

Star

  • +1
    TI__Mastermind 27321 points

    Hello Star,

    If RSOC_HOLD is set, it can hold the RSOC when there's drops in RM or FCC.

    What is the temperature? What does 5690 mean? Kelvin?

    Can you provide the full log and the settings?

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    TI__Genius 9645 points

    Hi Jose

    Thanks for your reply.

    What does 5690 mean?

    A: 5690 = 56.90 Celsius

    The RSOC_HOLD is not set. 

    Attached is our final product's gg file and drone BMS log.

    CR-BMS-G61 BMS_IC V07.gg.csvBMS_Log_20230727_162247.xlsx

    Please help check it.

    Thanks

    Star

  • 0 in reply to Star Xu
    TI__Mastermind 27321 points

    Hi Star,

    What is the matched ChemID? I need the ChemID to check bullet 4 (see below).

    Things they can try to improve the RSOC jump at the end:
    1-  change load select to 1, this uses the present average discharge current.
    2- Enable smoothing
    3- DO not set RSOC_HOLD and Smoothing at the same time
    4- Set Term Voltage to the steep zone of the OCV profile. 

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    TI__Genius 9645 points

    Hi Jose

    Thanks for your help.

    They have found the reason. To allow Drone to fly for an additional period of time, the system set a Delay of 10 seconds to display 0%.

    Another query is the voltage of the cell is significantly different from the other three battery cells, why is SOC still 11%?

    Waiting for your reply.

    Thanks

    Star

  • 0 in reply to Star Xu
    TI__Mastermind 27321 points

    Hi Star,

    The SOC reporting 11 when the cell-1 is 2.6V could be related to the delay of 10seconds.

    It looks like the gauge should report 0% based on configurations. Cell_term =1 in the settings.


    Another reason could be that the end of discharge voltage falls under the flat region. I will need to know the matched ChemID. You can provide the srec, or they can read ChemID (see below)


    As for the voltage imbalance seen above, is cell balancing enabled? Doing a sanity check in the schematic will also help identify this.

    Regards,
    Jose Couso