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BQ40Z50: The problem of battery capacity display for BQ40Z50

switch
Genius 3760 points
Part Number: BQ40Z50
Other Parts Discussed in Thread: BQSTUDIO

Tool/software:

Hi ti team，

When the battery power is remaining at 20%, make BQ40Z50 enter the shutdown mode. Insert the power supply to activate BQ40Z50 in about one month. At this time, the power display is only about 2%, but the actual battery capacity is far greater than 2%. Please analyze what causes the display error. Thanks!

  • 0
    TI__Intellectual 2020 points

    Hello,

    It's highly likely that the battery self discharged during the time the gauge was turned off. Could you send us the current gg file?

    Regards,

    Siddharth

  • 0 in reply to Siddharth Venkatesan
    Genius 3760 points

    Hi Siddharth，

    Please check the attachment.

    116AQ369-20-18650-4S1P-2600mAh-14.6V-BQ40Z50-R1-20190807.gg.csv

    Regarding the problem of the jumps in battery SOC and FCC Shutdown after activation, we hope to get technical assistance and explanations from TI.
    1. Why does it jump? It needs to be explained from the algorithm. Which parameters of the battery are related to SOC and FCC, and how are they calculated step by step?
    2. Why does RESET immediately correct SOC and FCC? Why is there a huge difference in the display of SOC and FCC after RESET and after normal activation?
    3. What happened to the chip after the battery SHUTDOWN? Why does it affect the display of SOC and FCC after battery activation?
    4. Are there any good solutions to the problem of SOC and FCC jumps after Shutdown activation?

  • 0 in reply to switch
    TI__Mastermind 28480 points

    Hello,

    switch said:
    Why does it jump? It needs to be explained from the algorithm. Which parameters of the battery are related to SOC and FCC, and how are they calculated step by step?

    There are a few reasons why the SOC could jump, however it is difficult to determine the direct root cause without a bqStudio log file depicting the gauge right before shutdown and after it has exited shutdown. The main parameters that relate to FCC and RemCap, which in turn are used to calculate FCC, are the chemID and values created by Qmax updates. For the exact way these values are calculated, please refer to the document below:

    https://www.ti.com/lit/an/slua364b/slua364b.pdf?ts=1723478240869 

    switch said:
    2. Why does RESET immediately correct SOC and FCC? Why is there a huge difference in the display of SOC and FCC after RESET and after normal activation?
    3. What happened to the chip after the battery SHUTDOWN? Why does it affect the display of SOC and FCC after battery activation?

    The gauge will go through a series of calculations after being reset or reentering normal mode from shutdown, where the open circuit voltage could potentially be off since being in shutdown for a extended period, which in turn could cause the FCC and SOC to change. However, if this is the case it should self correct after a cycle post exiting shutdown.

    switch said:
    4. Are there any good solutions to the problem of SOC and FCC jumps after Shutdown activation?

    If possible, can you please tell us the amount of variation between the FCC and RemCap there is before and after shutdown or share a log file?

    Regards,

    Anthony baldino