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BQ27520-G4: Could bq27520-G4 track cell impedance if exponential capacity drop is occured?

K.Yaita
Guru 29720 points
Part Number: BQ27520-G4

Hi Team,

Could bq27520-G4 track cell impedance if exponential capacity drop is occured as the following feature ?
I heard it seems Ra update has been disabled when the cell is aged from my customer.
Is it possible case?


Best Regards,
Yaita / Japan disty

  • 0
    TI__Mastermind 24870 points

    Hello Yaita-san,

    It depends on the certain application. Impedance Track can track impedance over the course of the battery. However, exponential decreases in impedance will be difficult to track. The best indication of the following behavior will be Qmax degradation.

    Thanks

  • 0 in reply to Kang Kang
    Guru 29720 points

    Hi Kang-san,

    Thank you for your kind support!

    >The best indication of the following behavior will be Qmax degradation.
    Is there any criteria about "Qmax degradation"?
    Could you tell me the detail?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    Guru 29720 points

    Kang-san,

    May I have your further comments?
    Your advice would be really appreciated.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Guru* 76230 points
    when you can only extract 80% of the original design capacity of the battery, it is needs to be replaced.
  • 0 in reply to Onyx Ahiakwo
    Guru 29720 points

    Hi Onyx-san,

    I appreciate for your kind support.

    >However, exponential decreases in impedance will be difficult to track.
    Could you tell me why it is difficult to track?
    I believe exponential degrades in impedance feature doesn't be assumed for bq27520-G4 but my customer want to know the detail.

    Any comments would be appreciated.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Guru* 76230 points
    Let me rephrase what i meant.. For the Qmax, you can easily tell that when the capacity is at 80% of design capacity the cell needs to be replaced. But for resistances there isn't a threshold where you say if the resistance has increased by X-times it needs to be replaced. The Ra tables gets updated as the cell is ageing and that will give good indication, but the qqmax is the best approach to tell when your battery needs replacement.

    thanks
    Onyx