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Trying to verify if the Impedance track algorithm on bq27421

Mike Koepke
Prodigy 335 points

I am trying to verify if the Impedance track algorithm runs on our system. Currently, I am facing issues as the Gas Gauge is

not detecting the discharge or Full charge conditions. I believe these are necessary condition for the algorithm to update Qmax and other battery parameters for gauging.

 

I am monitoring the Flags and Status register to determine the above conditions. Also I am referring  SLUA597 (Achieving Successful Learning Cycle)

to debug the steps one needs to follow so as to get the gauging to work.

Could you point me to the right resource for this as it would help save a lot of time figuring this out on my end?

  • 0
    TI__Guru* 76230 points

    Hi Mike,

    The default chem id pre-programmed in the guage may not be a good fit for your cells hence the gauge may not be a good fit for your pack. Do you have the BIN pin connected to ground via a 10k resistor. You can reach out to me directly so we discuss..

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    Prodigy 10 points

    Thanks Mike for posting here.Onyx, I get the correct CHEM_ID (0x128) and the BIN pin is connected as you mentioned.
    What I think the issue here is that I am looking for the sequence of changes in VOK,RUP_DIS,OCV,DIS,FC bits as per SLUA597 but not getting it.For example I charged the battery to 4.15V and 98% SOC to see if the FC bit is getting set,it was not and that is what I want to figure out.Maybe I am not starting the cycle properly during discharge,any pointers?

  • 0 in reply to aakash
    TI__Guru* 76230 points

    Aakash,

    There are criterias that ought to be met for those bits to get set or cleared. see attached pdf which you might find helpful. As for FC bit getting set you need to meet primary  charge termintionas describe in the technical reference manual of the guage. See attached

    8867.LearningCycleOverview_.pdf

    bq27421TRM.pdf

     

  • 0 in reply to Onyx Ahiakwo
    Prodigy 70 points

    Thanks for providing more information on this.I am using BQ27421-G1A which means there are no QEN,IT_ENABLE functions.

    Also I have doubts regarding relax state mentioned in the document.How do I achieve this state after a full discharge assuming the gas gauge itself is shutdown.Should I charge to a certain voltage and then let it discharge again?

    I understand you have provided detail of the steps but it will be good to have limits of current,voltage in every state as common problems mentioned talk about this.Also I am using a 630mAh battery and programming the gas gauge with Terminal_Voltage of 3.5V,Taper current 12.5