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BQ34Z100-G1: About loop count problem

Luo XiuFeng
Intellectual 676 points
Other Parts Discussed in Thread: BQ40Z50

Dear TI technologist:

After self-study, I changed the status to 02 and then performed charging and discharging to test if my equipment met expectations, but I was surprised:


1. Why does my full charge capacity display drop from 16.5A to 15.2A? After the discharge, my full charge capacity has dropped to 14.8A?


2. The number of cycles increases during discharge. During a complete charge and discharge process, my cycle count increased from 0 to 15, which is obviously problematic.

  • 0
    TI__Mastermind 25955 points
    Hi XiuFeng,

    When operating conditions change (such as temperature, discharge current, and resistance, and so on), it can lead to large changes of compensated battery capacity and battery capacity remaining. These changes can result in large changes of StateOfCharge(). When [SmoothEn] is enabled in Pack Configuration C, the smoothing algorithm injects gradual changes of battery capacity when conditions vary. This results in a gradual change of StateOfCharge() and can provide a better end-user experience for StateOfCharge() reporting.

    The RemainingCapacity(), FullChargeCapacity(), and StateOfCharge() are modified depending on [SmoothEn], as shown in the table found in section 7.3.6.15 of the datasheet.

    Please ensure you're using a learned pack with the proper chemID as the improper chemID and/or an unlearned pack may cause errant SOC/FCC jumps. Also, please make sure your parameters are set in the gauge with respect to your battery by following the step-by-step design procedure found in section 8.2.2 of the datasheet.

    Which cycle count? The CycleCount() 0x22? Please ensure your CC Threshold is set properly, ~90% of design capacity. The default value for CC Threshold in the gauge is 900 mAh... so an increase from 0 to 15 shows about 13,500 mAh passed during discharge if the default value was not modified to reflect the capacity.

    If issues persist after these modifications, please submit your gg.csv file and a log of the event.

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    Intellectual 676 points

    First of all, thank you for your reply. As you said, I adjusted the CC threshold from 900 to 14000, which is 90% of my full capacity, and I tested him. He did increase it only once during the entire discharge process. The explanation is valid. The only confusion I have now is whether the 14000 set at the CC threshold will never reach when the full capacity is reduced due to factors such as temperature, usage environment, and number of times.

  • 0 in reply to Luo XiuFeng
    TI__Mastermind 25955 points
    Hi XiuFeng,

    You're absolutely correct. Newer devices, such as the bq40z50 take this into account and have cycle count operate as a percentage of FCC, if desired.

    Sincerely,
    Bryan Kahler