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BQ27421-G1: Setting Data Memory

Hirokazu Takahashi
Expert 8420 points
Part Number: BQ27421-G1
Other Parts Discussed in Thread: BQ25890

Hello

We are BQ27421-G1 users.

 

I have a question about setting data memory.

Don't worry because the question number is our original.

 

Q9.   Is the SOC accuracy better if the SOC smoothing function is enabled?

 

Q10.  Is the value of Initial MaxLoad a value assumed by the user in advance? 

         Doesn't affect the algorithm because the initial value is updated?

 

Q11.   6.4.2.1.2 Is Ra Filter set by User? Learning and rewriting?

 

Q12.  What is Delta Voltage？(Min Delta Voltage、Max Delta Voltage)

 

Q13.  Can RASH current load (peak1.2A length 10msec) be average current and coulomb count accurately?

(Load Current sample.jpg)

 

Q14   Is it correct to set Default Design Cap to the same value as Design Capacity?

 

Q15.   6.4.2.1.12 Maximum Simulation Rate, Minimum Simulation Rate　Is it not necessary to set it?

 

Q16   Is it better to charge and discharge until the primary charge (charging completion) after setting Data Memory?

          Can you expect SOC stability?

 

Q17   As shown in this SOC_graph, if you discharge while charging and then charge while discharging after setting the data memory,

         the SOC will probably fluctuate rapidly due to voltage fluctuations. Is this because the data memory cannot be set properly and correctly?  (SOC_graph.jpg)

 

Q18.  The charging voltage of CHG_IC (BQ25890) is 4.208V. Should the value of "V at Chg Term" be adjusted to CHG_IC?

 

Q19.  Which of the data memory settings can be automatically rewritten periodically?

       Where is it in bq27421-G1Technical Reference?

 

Q20.  6.4.1.5.1 What happens if RMFCC of Operation Configuration (OpConfig) Register II is not set?

        Will FCC and RemainingCap change?

      

Thank you

  • 0
    TI__Guru 52115 points

    I see you asked quite a few questions. We need some time to go through the list and prepare the answers.

  • 0
    TI__Mastermind 24870 points

    Hello Hirokazu-san,

    Q9: It really depends. SOC smoothing just prevents jumps during the middle of a charge or discharge from some X percent to some Y percent, where X and Y are not 100% or 0%. It depends on customer definition of accuracy. We prefer to look at end of charge and end of discharge accuracy instead of overall discharge accuracy for TI.

    Q10: Yes, it is just an initial load. Load mode and select are the prediction engine along with their respective parameters such as Avg I or P last run. Please refer to the TRM.

    Q11: No, do not change this parameter. It is IT only.

    Q12: Delta Voltage is what the gauge tries to learn. Please refer to TRM. It is the dynamicness of the gauge.

    Q13: It depends, please do a test on the EVM and measure the gauge measured coulomb count in Passed Charge register and compare to machine integrated.

    Q14: No, default design capacity is a parameter of the chemID. It scales the resistance tables.

    Q15: No don't set these. This is only if your gauge does not fall within the necessary simulation rates set by these parameters. The default is normally good.

    Q16: Better to always reach primary charge termination

    Q17: The gauge state machine will try to compensate, but you should really have relaxation regions during the typical use case for impedance track. Otherwise, our OCV readings will become less accurate over time.

    Q18: No V at Chg Term is learned by the gauge.

    Q19: Almost all DF can be re-written by the host. The gauge re-writes Qmax, Ra tables periodically.

    Q20: This is just a sync bit during full charge determination. RemCap and FCC will still change.