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BQ40Z50-R1: BQ40z50-R1 parameter question

Hollis Liu
Intellectual 2595 points
Part Number: BQ40Z50-R1

HI team, 

I would like to know below parameter function, and how to set up them when i do a new design.

pack resistance(function, how to set up when design)

temp k(function)

temp a(function, difference with temp K)

Compres 0/1/2/3(how gauge calculate Compres 0/1/2/3 during discharging)

Thanks a lot. 

  • 0
    TI__Guru** 105770 points

    Hello Hollis,

    The pack resistance parameters are described in the TRM, it is all the series resistances added together of your system.Section 12.53 describes the components to consider. This is used parameter is used with turbo mode to help prevent the gauge from shutting down during current spikes at low SOC.

    These are calibration values for the temperature readings, depending on the thermistor used you may need to change them, but it is not recommended to use a different thermistor than the 103AT-2.

    The CompRes are values calculated based on the temperature relationship of resistance in the cells. If you check section 2.4 Update of Resistance in the app note on impedance Tracking: https://www.ti.com/lit/an/slua450/slua450.pdf

    It explains some of the relationships between resistance and temperature.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    TI__Intellectual 2595 points

    These are calibration values for the temperature readings, depending on the thermistor used you may need to change them, but it is not recommended to use a different thermistor than the 103AT-2.
    What will happen if we have error Temp a?

    What will happen if we have error Temp K?

    I would like to know how these 2 parameters affect the gauging and the difference between these 2 parameters. 

    The CompRes are values calculated based on the temperature relationship of resistance in the cells. If you check section 2.4 Update of Resistance in the app note on impedance Tracking.
    So CompRes is the actual resistance which is compensated by temp coefficient, right?

    Should CompRes keep changing during the discharging? We find sometimes the Compres change to 0 during the charging. Is that normal?

    Thanks

  • 0 in reply to Hollis Liu
    TI__Guru** 105770 points

    Hello Hollis,

    From the factory both of the parameters Temp A and Temp K should be setup for the 103AT-2. We don't recommend changing the parameters because it is hard to calibrate for a new thermistor. The only time they should be changed is for a new thermistor.

    You can review the TRM, the Temp A is the initial thermal factor and the Temp K is the scale factor.

    Yes that's correct, it can change as the temperature changes. It depends on what your values are that are used to calculate the resistance (Ra, Rb, and T) if it should be 0 or not, check the formula in section 2.5 Update of Temperature Model in the impedance track app note and see if you ca calculate it yourself to match.

    Sincerely,

    Wyatt Keller