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BQ40Z50-R2: FCC update anomaly at high current discharge

Yuxi Liu(Tony)
Expert 3090 points
Part Number: BQ40Z50-R2
Other Parts Discussed in Thread: BQ40Z50

Tool/software:

Hi TIer

The customer is a medical device application and needs to calculate the absolute battery power for low power shutdown, but the current FCC of the BQ40Z50 is very variable, not very good computing remaining life.

It has been confirmed that the customer's battery chemistry ID is correct given by TI and has gone through the learning process.

Customers have found that adjusting the meter simulation parameters for impedance tracking may be helpful for high current discharge devices, how do we adjust the following registers?

1. Prime Relax Time

2. Sec. Relax Time

3. Resistance Parameter Filter

4. Res Relax Time

5. Dis Relax Time Min

6. OCV Wait Time

Do you have any other suggestions? Thanks a lot

  • 0
    TI__Mastermind 28450 points

    Hello,

    We typically do not recommend changing these parameters.

    Is it possible to receive a log file of the situation and the .srec of the gauge settings so we can get a better understanding of the situation?

    Regards,

    Anthony Baldino

  • 0 in reply to Anthony
    TI__Expert 3090 points

    09AQ109-23-5187-3CYCLES-2024-1-9.gg.csvhttps://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/196/09AQ109_2D00_23_2D00_5187_2D00_3CYCLES_2D00_2024_2D00_1_2D00_9.srec

    Please see my input.

    For SOC jumps with high current outputs, is it due to slow OCV updates？Could we control the frequency of OCV updates?

  • 0 in reply to Yuxi Liu(Tony)
    TI__Mastermind 28450 points

    Hi Tony,

    Thank you for sending the gauge setting files, we will begin looking into them.

    I do not believe that slow OCV updates would cause SOC jumps with a high current output, since OCV measurements will not start unless the cell is in a truly relaxed state.

    If possible, can we receive a log file depicting the seen SOC jumps with the high current output? This will give us a better idea of what is occurring within the gauge calculations.

    Regards,

    Anthony Baldino

  • 0 in reply to Anthony
    TI__Expert 3090 points

    Hi Anthony

    Are there some updates, customers want to use the fuel gauge for battery health management, where battery life is currently calculated by dividing FCC by design capacity.

    Are there any other registers that can do this? 

    Is that what our SOC says？

  • 0 in reply to Yuxi Liu(Tony)
    TI__Mastermind 28450 points

    Hello,

    Yuxi Liu(Tony) said:
    Are there some updates, customers want to use the fuel gauge for battery health management, where battery life is currently calculated by dividing FCC by design capacity.

    I believe what you are referring to is the State of Health (SOH) register, where the device uses a value very similar to the FCC known as the SOH_FCC, and divides it by the design capacity to show the health of the cell. More information of how this is calculated for bq40z50 can be found below:

    Yuxi Liu(Tony) said:
    Is that what our SOC says？

    State of Charge is the depiction of where the charge is compared to the current Full Charge Capacity measurement. At full charge, this value should be 100% while at full discharge the value should be 0%.

    Regards,

    Anthony Baldino