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Poor accuracy of RSOC during low temperature discharge of BQ27z561 fuel gauge

Jason Zhou
Prodigy 190 points
Other Parts Discussed in Thread: GPCRB

Under the low temperature environment of -10℃, after calibration by GPCRB tool, under the environment of -10℃, the accuracy of RSOC during 2A constant current discharge is poor, more than 5%. The comparison between the log file and the discharge environment is shown in the figure below. Is there any reliable way to optimize RSOC in this situation? Thanks!

  • 0
    TI__Guru** 102415 points

    Hello Jason,

    It looks like only one of the packs out of multiple were over 5% SOC error, can you share the data logs along with the .gg files for their testing? What are the differences between the lower accuracy cells and higher accuracy?

    I would try to perform a couple discharge tests at lower temperature and see if this error is corrected on the second discharge.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    TI__Prodigy 190 points

    Thank you very much for your answer, sorry, because of the confidentiality of customers, I cannot provide these documents for the time being. The batteries with lower precision and higher precision are the same type of batteries, except for individual differences, there is no other difference. Are you asking me to do an experiment? Can it be understood as the difference caused by the inconsistency of low temperature cells? The model calibrated by the GPCRB tool at low temperature is not necessarily suitable for every battery, so there is such a large accuracy error?

  • 0 in reply to Jason Zhou
    TI__Guru** 102415 points

    Hello Jason,

    I am asking if there was any difference in the configuration of the gauge between the tests, or all were using the same cell, same board, and same settings? It looks like all the steps were completed to help with cold temperature accuracy.

    We may not be able to help much further without reviewing the data. Send a DM with private information if needed.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    TI__Prodigy 190 points

    The configuration and test conditions of all software are the same, can you please give a possible reason, or how to optimize it

  • 0 in reply to Jason Zhou
    TI__Guru** 102415 points

    Hello Jason,

    To help more we would need the data from the tests and their configuration files from the gauges and cells they are testing before and after the test. It looks like most of the accuracy is fairly close for the 3 samples tested, sample 3 is just a little over 1% higher max error. At cold temperatures, a very small difference with the Rb values can cause a large change in the SOC since internal resistances increases significantly in the cold.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    TI__Prodigy 190 points

    Thank you for your answer, I uploaded the files comparing RA and RB, the program files after GPCRB, and the precision test experiment of RSOC, looking forward to your answer!

    5277.information.xlsx

    2146.M11A_Ra_table.xlsx

    6404.M11A-ID5870-20220808.gg.csv

  • 0 in reply to Jason Zhou
    TI__Prodigy 190 points

    Hello, sorry to bother you, do you have the latest results now?Thank you, looking forward to your reply

  • 0 in reply to Jason Zhou
    TI__Guru** 102415 points

    Hello Jason,

    I don't see any issues in the data, it looks like multiple packs were tested to get the average Ra and Rb tables, along with Qmax. It seems like very thorough testing.

    It looks to me that the gauge with over 5% error may have updated the resistances slightly different on one of the previous cycles, or had slightly different Tk and Ta values which caused a slightly higher error. As I mentioned, at extreme cold temperatures, even a very small change can cause a large difference in our estimation due to the thermal modeling.

    Sincerely,

    Wyatt Keller