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BQ20Z65-R1_BQEVSW-SW: Max Error Clarification

Thomas CN1
Intellectual 300 points
Part Number: BQ20Z65-R1

The BQ20Z65-R1 user manual explains the MaxError in section A.13 as below.

'Max error is incremented internally by 0.05% for every increment of CylceCount after the last QMAX
update. MaxError is incremented in the display by 1% for each increment of CycleCount'

Please elaborate on this: What meant by internally 0.05% and in the display 1% here?

Regards,

Thomas CN

  • 0
    TI__Guru 57697 points

    Hello Thomas,

    Internally means in the firmware - this is used to apply limits/filters int he algorithm. This is not readable from the gauge.

    Display means the MaxError() read out from the gauge.

  • 0 in reply to Shirish
    Intellectual 300 points

    Hi Shirish,

    Thanks for the reply.

    In this case the correct statement shall be 'MaxError is incremented in the display by 1% for each 20th increment of CycleCount', right? 0.05% increment internally per cycle count will result for 1% increment externally at every 20th cycle count. Please correct me if my understanding is wrong.

    Regards,

    Thomas CN

  • 0 in reply to Thomas CN1
    TI__Guru 57697 points

    Hello Thomas,

    There is an internal variable that is updated by 0.05. That variable is used to adjust MaxError() based on other factors. So the inference that "for each 20th increment of CycleCount" is not applicable. MaxError() can be changed by the gauging algorithm. If cycle count was the only criteria to update, then reading out MAxError() would not be that useful as the host can also compute it.

  • 0 in reply to Shirish
    Intellectual 300 points

    Hi Shirish,

    Thanks for the clarification that the MaxErr is  not only based on the cycle count. 

    Can you please elaborate a little more for our understanding what are the parameters impacting the MaxErr other than cc? Is there any documentation explaining this?

    We sometimes see in our application that the MaxErr is getting set back to 1% after reaching to 4%. Is this expected behavior? And what could be the reason for this?

    Regards,

    Thomas CN

  • 0 in reply to Thomas CN1
    TI__Guru 57697 points

    Hello Thomas,

    It is normal for MaxError to change from cycle to cycle. It is an indicator of the estimated error in RSOC. It depends on many conditions. The main reason MaxError increases is when the battery does not fully charge and fully discharge in many continuous cycles with no rest in between. When it gets too high we recommend a "conditioning cycle" which is just a full charge/discharge (similar to learning cycle).