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BQ27441-G1: Designing with BQ27441DRZT-G1B

Shibin Varghese
Intellectual 835 points
Part Number: BQ27441-G1

Hello Team,
I am using BQ27441DRZT-G1B in one of our designs.
Could you please explain how the fuel gauge measures the remaining capacity?
What is the difference between TrueRemainingCapacity()  and RemainingCapacityUnfiltered() and RemainingCapacityFiltered()?.

  • 0
    TI__Guru 57697 points

    Hello Shibin,

    When smoothing is enabled, true values may be different from reported values. Filtered values are the smoothed values.

    The fuel gauge uses the impedance track algorithm to measure remaining capacity.

  • 0 in reply to Shirish
    Intellectual 835 points

    Hello Shirish,
    Thank you for your reply.
    I am using a 2000mAh battery.
    3.7V nominal voltage 
    4.2V maximum voltage.
    Attached is the battery voltage reading and the SoC data I've collected.

    When the battery is charging, the battery voltage is 4183mV and the SoC is 62 and the remaining capacity is 1209.
    When I terminated the charging, the ADC voltage will become 4154mV.
    If I reinitialize the fuel gauge, the SoC will become 90 with 1729 remaining capacity.

    What may be the reason for the SoC to raise even when the charger is not enabled but just reinitialized the fuel gauge?

  • 0 in reply to Shibin Varghese
    TI__Guru 57697 points

    Hello Shibin,

    The gauge has different operating modes and there are flags to indicate it. On POR, the gauge can only come up with a best case estimate which will be wrong if the battery has not been at rest.

    See section 2.4 Operating Modes of TRM www.ti.com/.../sluuac9a.pdf

  • 0 in reply to Shirish
    Intellectual 835 points

    Hello Shirish,
    Could you please explain why is
    When the battery is charging, the battery voltage is 4183mV and the SoC is 62 and the remaining capacity is 1209.
    When I terminated the charging, the ADC voltage will become 4154mV.
    If I reinitialize the fuel gauge, the SoC will become 90 with 1729 remaining capacity.

  • 0 in reply to Shibin Varghese
    TI__Guru 57697 points

    Hello Shibin,

    The battery must be in a state of rest to get an accurate estimate. In this case the voltage is still stabilizing after the charge.

    Is the correct chemistry ID is programmed to the gauge?