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Original question:

BQ27426: Related problems of Fast Qmax 1

BQ27426: Related problems of Fast Qmax 2

xianzhen cao
Prodigy 100 points
Part Number: BQ27426


Dear engineers of TI:

When BQ27426 is used in our project, we have some questions about Fast Qmax:

1、offset：39

What does the value of the register mean? What does "Number" in "Number of Fast Qmax measurements" mean?

2、offset：43/44/45/46

How can these four registers be modified when default values are not used? Or, what is the impact on battery life and measurement accuracy?

thanks!

  • 0
    TI__Guru 64266 points

    #1: The gauge calculates Qmax based on point measurements (current, voltage and temperature). It will require that depth of discharge > Fast Qmax End DOD and that the number of point measurements is > Fast Qmax Min Points before it calculates Fast Qmax.

    #2: These registers control how much change in Qmax the gauge allows. In general, Qmax should not rise during use. It will diminish over time. However, especially with Fast Qmax, there's always the possibility of a measurement error so the gauge applies limits to avoid gross errors in Qmax. These registers control these limits. For example, if you think that your cell may actually have 150% Qmax vs. the default Qmax value, then you can set Maximum % Default Qmax to 150%. Qmax is key for accurate gauging, so if you set these values, and especially if you adjust the other Qmax algorithm parameters that restrict Qmax updates, then chances increase that the gauge will calculate inaccurate Qmax and gauging will be negatively impacted.