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BQ4050: inaccurate state of charge

Jonathan Navor
Genius 9475 points
Part Number: BQ4050
Other Parts Discussed in Thread: BQSTUDIO

Hi Team

Good day and we need your assistance.

With regard to the BQ4050 scheme, an exception occurred to the customer. After his rsoc was fully charged or when the charger is disconnected and the device is turned on for operation, it becomes 90%
This is not the change after continuous discharge, but the state that it is unplug the communication cable to read after the rsoc changes after the startup.
Here is the attached image of two state below.

Best regards,

Jonathan

  • 0
    TI__Guru** 105760 points

    Hello Jonathan,

    When the gauge resets it will take an assumed OCV reading (or whatever voltage is present on the top of stack) and use that to estimate the SOC. If the voltage is not relaxed then the SOC may not be accurate for the initial estimation. The voltage must be stable for accurate gauging when the gauge goes from shutdown or power removed to an active state.

    Sincerely,

    Wyatt Keller

  • 0
    Prodigy 20 points

    This state does not occur when the machine is reset. The whole process is complete. When the machine is fully charged to 100%, it will turn to 90% when the machine is started. There is no other action in the process.

  • 0
    Prodigy 20 points

    This state does not occur when the machine is reset. The whole process is complete. When the machine is fully charged to 100%, it will turn to 90% when the machine is started. There is no other action in the process.

  • 0 in reply to Wyatt Keller
    TI__Genius 9475 points

    Hi Wyatt,

    Good day! Thank you for your response. 

    Wyatt Keller said:
    When the gauge resets it will take an assumed OCV reading (or whatever voltage is present on the top of stack) and use that to estimate the SOC. If the voltage is not relaxed then the SOC may not be accurate for the initial estimation. The voltage must be stable for accurate gauging when the gauge goes from shutdown or power removed to an active state.

    What I understand on this is that this is a different problem. I believe you are telling that the initial RSOC is determined by the voltage when the battery is reset, but there will be deviation because the voltage is not static. 

    However, the problem is that when the battery is fully charged, the RSOC becomes 100%, and when the charger is removed, the machine is turned on, the RSOC directly becomes 90%. What is the possible reason?

    Best regards,

    Jonathan

     

  • 0 in reply to Jonathan Navor
    TI__Guru** 105760 points

    Hello Jonathan,

    The CEDV based gauges use coulomb counting for a majority of the gauging, so jumps are not as common when fully charged, we apply voltage based corrections at the end of discharge with the EDV points. Can you share a BQStudio log showing this behavior along with the .gg file? We will need to look at the register settings and flags set during the test to get a better understanding of what the gauge is doing.

    Sincerely,

    Wyatt Keller