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Original question:

BQ27426: Reason why different battery Fuelgauge get different FCC values on initial power up?

BQ27426: Schematic diagram of FCC prediction and understanding of each parameter

Wang Dong
Intellectual 580 points
Part Number: BQ27426

Hello，

Attached is a compilation of the FCC's prediction schematic and the meaning and understanding of each parameter in the FCC's formula, could you please help me to confirm if it is correct?

Thank you!

E2E_Consult the conditions for each parameter in the FCC formula.zip

  • 0
    TI__Guru** 103205 points

    Hello Wang,

    DODatEOC is updated when temperature changes or charge termination occurs. It is the DOD point at the moment of VCT so DODatEOC = f(I,T,V). It is corrected based on the current and the Ra/Rb table.

    FCC will drop after each cycle as the gauge learns the parameters of the old cell (in your example of inserting 80% SOH cell)

    Please use our Impedance Track FAQ in order to verify your equations, it should be well documented in our documentation: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1100653/faq-impedance-track-faqs

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Intellectual 580 points

    hello，

    Does the DODatEOC only update when the temperature changes and charging stops? Doesn't it update when charging starts?

    Please help to reply in detail in the attached Excel, thanks!

    There are three questions in Excel, please help to reply.

  • 0 in reply to Wang Dong
    TI__Guru** 103205 points

    Hello Wang,

    Please clarify which questions, I believe I answered most of the questions in the Excel.

    The questions are asking for very specific descriptions and requesting specific answers, but we do not have enough information to answer some of these questions.

    Q1: Not sure why learning is happening on aged cell, FCC would not necessarily be constantly lowered during learning and if the learning is occurring all gauge related information should be disregarded.

    Q2: FCC is a very simplified method where DODfinal will change often depending on the temperature and load.

    Q3: was answered previously.

    Sincerely,

    Wyatt Keller