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BQ40Z80: BQ40z80 RSOC jump after a period of standing

feng
Prodigy 170 points
Part Number: BQ40Z80
Other Parts Discussed in Thread: GPCCHEM

Hi,TI's Expert

  I've met a issue about using BQ40z80, Here is the desciption.

  When I test the battery discharge from a HV status(like 90% RSOC) to LV status (like 10% RSOC) within a 0.5C current. After the test finish and a period RELAX time(like 10 hours).Then the RSOC jump to a higher value like 16% - 21%. which means the RSOC increased without chargeing.

  From the BQ40z80 TRM,I've tried disable the RELAX_JUMP_OK bit and nothing changed.

  I put the .gg file in the attachment,please take a look and give me some advice.

  Thanks.bq40z80.csv

  • 0
    TI__Mastermind 28470 points

    Hello,

    Would it be possible to receive a log file depicting the situation above? This would allow us to take a deeper look into what is occurring within the gauge.

    Regards,

    Anthony Baldino

  • 0 in reply to Anthony
    Prodigy 170 points

    Thanks for reply.

      It take some time to log that because the machine are underuse now.

      The attach log file also have the issue which in charge process, after 5hours standing the RSOC has changed, also RC and FCC changed. 

      I think there are the same issue in charge and discharge prcess.bq40z80_log.xlsx

  • 0 in reply to Anthony
    Prodigy 170 points

    Further more, I think the issue may have a connection with the bit RELAX_SMOOTH_OK. 

    From the spec, the RELAX_SMOOTH_OK bit may can fix the error of charge OR discharge so it will appear a smooth RSOC increase OR decrease.

    So when I cfg the bq40z80, I enabled this bit like TI's srec file did, and the same Smooth Relax Time.

  • 0 in reply to feng
    TI__Mastermind 28470 points

    Hello,

    Thank you for sending those files over, we will begin to take a look into them. If possible, can you please also tell us how the ChemID was chosen for this gauge? Was the GPCCHEM tool used to find an appropriate match?

    Regarding the RELAX_SMOOTH_OK, it is not able to completely rid the error, however it smooths out the changes in RSOC over a period of time, unlike RELAX_JUMP_OK where it is allowed to change freely.

    Upon initial glance of the log file, I see the temperature reading from TS2 is around 210 degrees C. Is this thermistor in use? If so, can you please explain why this might be occuring?

    Regards,

    Anthony Baldino

  • 0 in reply to Anthony
    Prodigy 170 points

    hi, Thanks for reply.

      I follow the spec which is SLUA848 demonstrated. And the file return form TI as this:bq40z80-report.zip

      As for the Temp sensor, I just enabled the TS1, any other sensor are disabled.

  • 0 in reply to Anthony
    Prodigy 170 points

    From the log file above provided, found that before RSOC changed, the [CB] function has been  set.

    So I disabled the  CB bit and testd again in the machine, and there are also a RSOC jump from 10% to 17%

  • 0 in reply to feng
    TI__Mastermind 28470 points

    Hello,

    Thank you for sending that over. It seems like the chemID chosen is applicable since the given DOD error is less then 3%.

    If possible, can you please send the completed learning cycle log? I see that the Qmax is jumping to a much higher values around 2700mAh compared to the inputted design capacity value of 2200mAh.

    Regards,

    Anthony Baldino

  • 0 in reply to Anthony
    Prodigy 170 points

    Hi, Thanks for reply.

      yes, when I look back the cfg file, I also found the Design capacity is filled wrong. Cause the primary cell capacity is 2200mah and the new cell capacity is 2500mah. Now I've changed the value and testing now.

      And  I wanna ask that,  if there is a RSOC rise is normal phenomenon while the Design capacity value don't match the real cell ?

      If yes, why is that OR what's the mechanism

    Regards

  • 0 in reply to feng
    TI__Mastermind 37761 points

    Hello,

    Today's a holiday and no one is in the office. We will get back to you tomorrow.

    Regards,

    Nick Richards

  • 0 in reply to Adrian
    TI__Mastermind 28470 points

    Hello,

    Yes, the RSOC jumping can be caused by not setting the Design Capacity properly when the learning cycle has been completed since many of the calculations are reliant on the Design Capacity value. When Qmax is also being calculated for the first time during the learning cycle, this value not being set correctly can affect that value.

    Regards,

    Anthony Baldino