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BQ34Z100: Functionnement specification

Hocine BELHAOUES
Prodigy 40 points
Part Number: BQ34Z100

Tool/software:

Hi,

We plan to integrate the BQ34Z100 into one of our applications and I’d like to clarify one point. Many fuel-gauge ICs rely on full charge/discharge cycles DURING OPERATION (vs Learning Cycle procedure) to update their Qmax value, but I haven’t been able to find such a procedure in the BQ34Z100 documentation. From what I’ve read, the gauge recalculates Qmax automatically by comparing OCV readings taken at two different DOD (Depth of Discharge) points. Is my understanding correct, or does the BQ34Z100 actually require—or internally perform—a dedicated deep-cycle routine to update Qmax?

Regards

Hocine

  • 0
    TI__Mastermind 26845 points

    Hello Hocine,

    The qmax is set with the learning cycle that is attached below but afterwards it is internally update to reflect the cell as it ages.

    Learning Cycle:
    /cfs-file/__key/communityserver-discussions-components-files/196/How-to-Complete-a-Successful-Learning-Cycle-for-the-BQ34z100.pdf

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Prodigy 40 points

    Hello Alan,

    I understand that Qmax is calculated during the learning cycle phase. My question is: once the system is in operation, is it necessary to perform a full (deep) charge, or are the OCV measurements and internal resistance calculations sufficient to recalibrate Qmax?

    Regards

    Hocine

  • 0 in reply to Hocine BELHAOUES
    TI__Mastermind 26845 points

    Hello Hocine,

    Hocine BELHAOUES said:
    is it necessary to perform a full (deep) charge

    It is not necessary the Qmax would update progressively as you are using the gauge meaning that it would do the OCV measurements and internal impedance of the cell without user intervention.

    Thank you,
    Alan

  • 0
    Prodigy 40 points

    Hi alan,

    Thank you for your reply.
    Another point: I would like to perform tests with OCV measurements after short relaxation periods.
    For these tests, I set the ResRelax Time, Dsg Relax Time, and Chg Relax Time registers to 60 seconds.
    During the tests, after 60 seconds of rest, the FirstDOD flag changes to 1, but OCVTAKEN remains at 0.
    It only switches to 1 precisely after 3600 seconds.
    Does an internal mechanism enforce a fixed 3600-second delay before validating an OCV measurement during the relaxation period, or is there a parameter that I might have missed?

    Regards

    Hocine

  • 0 in reply to Hocine BELHAOUES
    TI__Mastermind 26845 points

    Hello Hocine,

    I would need to get back to you on that and discuss with my team about the internal mechanism for OCV measurements.

    Thank you,
    Alan 

  • 0 in reply to Alan Frias
    Prodigy 40 points

    Hi Alan,

    ok thank you

    Regards

    Hocine

  • 0 in reply to Hocine BELHAOUES
    TI__Mastermind 26845 points

    Hello Hocine, 

    After discussing with my team we were able to conclude that the OCV measurements are taken after 6 minutes in relax mode when the current is below 4μA than a OCV measurement would take place however if these requirements aren't meant than 3600 seconds would be the period of a OCV measurements.

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Prodigy 40 points

    Thanks for your response.

    Is the 4 µV condition configurable? I couldn’t find any parameter that allows it to be modified.

    I’m trying to verify the proper operation of the OCV measurement and the update of the State of Charge (SoC). To do so, I initially connect a battery after a reset. The SoC is correctly evaluated at startup.

    Then, I replace the battery (without cutting power) with another one having a different SoC. However, the system continues to report the previous SoC. I attempt to force an OCV condition: no current flows (the battery is connected directly, not through the BQ), but after 3600 seconds, the OCVTAKEN and VOK flags are set, indicating that an OCV measurement has been taken.

    My confusion is that despite this, the State of Charge is not updated.

    Could you please help me understand how I can reliably ensure that the SoC is refreshed? I’m also looking for a procedure that can ensure daily SoC updates based on OCV measurements.

    Best regards,

  • 0 in reply to Hocine BELHAOUES
    TI__Mastermind 26845 points

    Hello Hocine,

    Hocine BELHAOUES said:

    Is the 4 µV condition configurable? I couldn’t find any parameter that allows it to be modified.

    No this is a default values and can't be updated 

    Hocine BELHAOUES said:
    Could you please help me understand how I can reliably ensure that the SoC is refreshed? I’m also looking for a procedure that can ensure daily SoC updates based on OCV measurements.

    -SOC gets constantly updated through the charge, relax and discharge cycles however it will not accuracy update instantly with a new cell while in use. The battery gauge isn't meant to have the ability to hot swap a battery out for a new cell and then read the new SOC.

    Hocine BELHAOUES said:
    I can reliably ensure that the SoC is refreshed?

    -Run discharge, charge and relax cycles and you will see the capacity update along with the SOC and you can perform the same test with different test equipment and with the same cell and see the same results from the test

    Thank you,
    Alan