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BQ34Z100-G1: The SOC drop to zero

Big Bill
Expert 1980 points
Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: GPCCHEM

4101.log.xlsxDear All:

     

        I used the BQ34Z100-G1 to measure the 8S1P PACK， I  made ten  prototypes, the most of  which are  OK, but two of them are bad. the bad prototypes shows the phenomenon  that  the SOC drop about 40% to 0% in an instant. Pls refer to the attachment and picture. I program the same SREC profile. and calibration the voltage  ,current follow the procedure. Can you help me to solve the problem~ Thanks

 

  • 0
    TI__Mastermind 25955 points

    Hi Bill,

    Thank you for the log.  Did you use the GPCCHEM tool to determine a matched chemID for the cells, program them chemID to the gauge, then run a learning cycle to learn the pack?  If not, this will cause the issue seen above.

    If the problem persists after performing the above steps, please also send your gg.csv file that includes your gauge settings, and let me know which chemID you're using.

    Sincerely,
    Bryan Kahler

    Find out more about the BQ34Z100-G1 including technical documents and tools/software/firmware and frequently asked questions.  Refer to the quickstart guide to get up and started. Also, learn how to find your chemID and perform voltage and current calibration.

  • 0 in reply to Bryan Kahler
    Expert 1980 points

    1391015.gg.zipDear  Bryan:

        I have do the Chem ID  and  run  a learning  cycle,   As I already said, only two of the 10 prototypes have such problems.  The attachment is the GG  file. The Chem ID is 2055, the Chem ID is right.

  • 0 in reply to Bryan Kahler
    Expert 1980 points
    Dear Bryan:

    Can you update the issue ？ Thanks~
  • 0 in reply to Big Bill
    TI__Mastermind 25955 points

    Hi Bill,

    With a partial log its difficult to tell, however, It appears that the terminate voltage of the cell may be incorrect.

    What is the terminate voltage of the cell listed in the datasheet?  The default value of 3000 mV is being used.

    When terminate voltage is reached (3000 mv * 8 = 24000 mV), SOC drops to 0% because terminate voltage is defined as 0% SOC.  At this point Rempcap is set to 0 and FCC is recalculated.  As shown below, the device keeps discharging and the passedQ continues to increment. Another simulation is run, remcap and SOC remain 0 because the gauge is below terminate voltage and FCC is recalculated.

    Please modify the value of Terminate voltage to match that of the cell and rerun the test.

    If this does not help, please modify the Average I last Load to 13000 mAh and rerun the test, or change load select to 6 and set User-Rate MaH to 13000.

    Sincerely,

    Bryan Kahler

  • 0 in reply to Bryan Kahler
    Expert 1980 points
    Dear Bryan:

    Thanks for your reply. I am sorry to tell you it's hard to for me to modify the terminate voltage because the product is hard to disassemble
    In my application, there are two load mode, one is high loading that is about 13000mAh, and the other mode is 5000mAh, in the 13000mAh loading mode it take 9 minutes that more than 500s, but it will be less than 500s in abnormal situation such as this faulty machine. can i run the 5000mAh loading mode to update the Average I last load to solve the issue？ Look forward to your reply， Thanks~
  • 0 in reply to Big Bill
    TI__Mastermind 25955 points
    Hi Bill,

    Please modify the Average I Last Load in dataflash to the expected load for the test. If the 5000 mAh loading mode is run before the 13000 loading mode, Average I Last Load should update to ~5000 mA prior to the 13000 mA test. This may improve results, but may still result in a SOC drop.

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    Expert 1980 points
    Dear Bryan:

    Thanks for your support！ I modify the Average I last Load to 13000mAh , it's OK!
    How can I improve this issue in the previous design？
  • 0 in reply to Big Bill
    TI__Mastermind 25955 points
    Hi Bill,

    Two options:

    1) Unseal the devices and change the value via I2C
    2) Fully charge your device and then discharge at 13000 mA for at least 530-600 seconds for a qualified discharge that will update Average I last load. If your battery is too small to discharge at that rate for at least 530-600 seconds:
    (a) discharge at as high as possible for 530-600 seconds to get close - OR -
    (b) Use a power supply in place of the battery and discharge at 13000 mA for at least 530-600 seconds.

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    Expert 1980 points
    Dear Bryan:

    Thanks for your support~ what cause the issue？ What are the specific reasons？ Thanks！
  • 0 in reply to Big Bill
    TI__Mastermind 25955 points
    Hi Bill,

    The last load at 13000 mA did not last for at least 530 s, the required time for to be a qualified discharge that will update Average I last load. Since the Average I last load was not updated for this higher rate, the last qualified discharge set the Average I last load, a much lower rate. The calculation was based off the lower rate. Updating for the higher rate allows the calculation to be based off of the higher rate.

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    Expert 1980 points
    Dear Bryan:

    Thanks for your help. as your said the Average I last load is update after the discharge cycle,. but I do the learning cycle by the 0.2c discharge. i can't see any change in the Average I last load value , it's still -299ma. What's wrong with my understanding?
  • 0 in reply to Big Bill
    TI__Mastermind 25955 points
    Hi Big Bill,

    To update the Average I Last Load for the next cycle, the current cycle will need to be run for at least 530 s at that current. Once the device has discharged without interruption for at least 530 s, the discharge is considered qualified and will update the average i last load value in the device.

    If the issue persists, please send a log of the event and the gg.csv of your settings.

    Sincerely,
    Bryan Kahler