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BQ34Z100-G1: Incorrect SOC Reported when RUP_DIS is set.

Kirk Baumgartner
Prodigy 20 points
Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQ34Z100

I have a battery pack with a BQ34Z100 running a golden image that was created on another pack.  The fuel gauge was reporting a 70% state of charge when the battery voltage was 21.7V.  For this pack the charge voltage is 25.8 and the terminate voltage is 20.1V.  I noticed that the RUP_DIS bit was set and the Qmax time was 2032.  I sent the IT ENABLE command to the fuel gauge, this cleared the RUP_DIS bit, the SOC dropped to 2% and QMax updated indicated by the QMax time dropping to 0.  This raises the following questions:

1. What causes the RUP_DIS bit to be set?

2. If the RUP_DIS bit is set, is it OK to send the IT ENABLE command during charge or discharge or will that interfere with the coulomb counting?

3. What are the units of Qmax time?

Thank You,

Kirk Baumgartner

  • 0
    TI__Genius 12215 points

    1. RUP_DIS shall set before IT Enable command is sent, or set when the impedance calculation result is negative
    2. IT Enable had better not be sent during charging or discharging, it had better to be sent during relax and the voltage has been stabilized.
    3. The unit of the Qmax Time is hr/16
  • 0 in reply to Steven Yao
    Prodigy 20 points

    I should have mentioned that the learned status was at 6 for this fuel gauge.  Just a few follow-on questions:

    1. Is the RUP_DIS bit set immediately upon calculation of a negative impedance value or are the IT learning configuration values applied to measurement and the result of that calculation is negative?  The pack in question has more aggressive IT learning parameters, I am hoping a recent change to the learning settings to make them more conservative will help reduce the incidence of RUP_DIS being set.

    2. On a discharge cycle where the RUP_DIS is set would you expect the SOC values for the remainder of the discharge to be reasonably close and following discharge cycles would be less and less accurate or are the SOC values no longer useful after the bit is set?

  • 0 in reply to Kirk Baumgartner
    TI__Genius 12215 points

        RUP_DIS will be set once newly calculated impedance value is negative.    

        Once RUP_DIS is set, impedance and Qmax update will be disabled, coulomb will be still underway, but the result will be dubious,