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BQ40Z50-R2: Application issues

lan xin
Prodigy 120 points
Part Number: BQ40Z50-R2
Other Parts Discussed in Thread: BQSTUDIO

Tool/software:

Hi，I applied the bq40z50-r2 device to a 2S1P battery pack, extracted the chemical ID, and after completing the learning, I was able to accurately estimate the battery level and full charge capacity accuracy, and used it in practical application scenarios without any problems. But when I used it in bulk, I found that two new batteries suddenly had their FCC drop from 2100mAh to 900mAh during discharge, and their SOC suddenly changed from 55% to 0. From the logs obtained from our application device, we did not find that the battery cell voltage had reached the cut-off voltage. I know that when the cell voltage reaches the cut-off voltage, there will be a SOC jump to 0, but obviously it is not the reason. Due to the low probability of occurrence, Battery Management Studio cannot be used to collect logs. Therefore, please provide some possible reasons for this abnormal situation. thank you

  • 0
    TI__Mastermind 25315 points

    Hello,

    Attached is an document that contains information regarding end of discharge drops:

    https://www.ti.com/lit/pdf/sluaa45

    Regards,

    Anthony

  • 0 in reply to Anthony
    Prodigy 120 points

    Hi，The battery pack does not operate below 0 ° C, and this is not a batch issue. It is just two individual cases. I have collected some voltage, current, temperature, and FCC data when there is a jump to 0. Additionally, please help check if my gg.csv file is related to the estimation model or other anomalies. My chemical ID is 2931, thank you！

    Soc_Jump_0.zip

  • 0 in reply to lan xin
    TI__Mastermind 25315 points

    Hi Ian,

    Thank you for sending these files, it is difficult to determine a root cause of the SOC drop without a bqStudio log. Was there any difference in the load or set up for these two individual cases?

    We will look into these files in the mean time.

    Regards,

    Anthony

  • 0 in reply to Anthony
    Prodigy 120 points

    Hi，Anthony，

    I used Battery Management Studio to capture two sample log data and reproduced the situation where RSOC jumps to 0 and FCC becomes a small value. I found that the low-temperature high current load model can cause a sudden change in FCC estimation. Please analyze the logs to understand why FCC and remaining capacity undergo a direct change rather than a smooth calculation. Based on the actual situation, the battery pack can still continue to discharge because my cell voltage has not reached the cutoff.

    case3_error.zip

    case5_error.zip

  • 0 in reply to lan xin
    TI__Mastermind 25315 points

    Hi Ian,

    Thank you for sending these files over, we will begin analyzing them.

    lan xin said:
    I found that the low-temperature high current load model can cause a sudden change in FCC estimation.

    Is this low temp high current load model used in all packs and not just these two cases? Are there any other differences in the load between the functioning cases and non-functioning cases?

    Regards,

    Anthony

  • 0 in reply to Anthony
    Prodigy 120 points

    Yes, applicable to all battery packs. The case I designed was simulated based on actual loads, as we are using unmanned aerial vehicle products, there may be significant fluctuations in current. How to optimize this situation and whether it is necessary to change the load select, currently set to 7. I tried to set the load select to 1. Under the same load simulation, the same battery pack with load select=1 did not experience any jump to 0 and completed the discharge process normally. The specific data can be found in the attached log. Also, please provide a detailed description of the 8 load models and their applicable scenarios. Thank you

    caseA.zip

    caseB.zip

  • 0 in reply to lan xin
    TI__Mastermind 25315 points

    Hi Ian,

    In the log file, it does seem like changing the load select to 1 was able to offer better performance. Since the Remaining Capacity value used in the SOC calculation relies on a voltage simulation that is based on the Load Mode/Load Select, we would recommend keeping it at 1. The document below in section 2.2 has more extensive information regarding each load select.

    http://www.ti.com/lit/pdf/slua948 

    Regards,

    Anthony

  • 0 in reply to Anthony
    Prodigy 120 points

    Hi，

    After changing the load select to 1, I sent a reset command to refresh, but now there is an issue where the reset command disconnects the external power supply, causing the battery powered device to lose power. May I ask if it is possible not to use the reset command? Will it have any impact if not used? Or there are other commands that can replace the reset operation. I don't want power outages to occur

  • 0 in reply to lan xin
    TI__Mastermind 25315 points

    Hi Ian,

    What conditions are the gauge under when the reset is sent? The gauge should initialize once the reset has been completed.

    Regards,

    Anthony

  • 0 in reply to Anthony
    Prodigy 120 points

    Hi，

    Before and after resetting, only the value of load select is changed. I mainly need to upgrade to change the value of load select to 1. Therefore, is it necessary to send a reset command to initialize the device after modification, or not execute the reset command? Will the device adjust according to the modified load model after load select

  • 0 in reply to lan xin
    TI__Mastermind 25315 points

    Hi Ian,

    Would it be possible to change the load select, then pull a new .srec of the device? This would allow for the load select to not be changed on any devices and the device would not be needed to be reset.

    Regards,

    Anthony