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BQ40Z50-R1: Wrong FCC simulation on wake up after SHUTDOWN

Pietro Vignali
Intellectual 925 points
Part Number: BQ40Z50-R1

Hello,
I'm currently trapped in a weird problem.
When the bq40z50-r1 wakes up after SHUTDOWN, it calculates a wrong FCC, much different from that it calculates if I apply a RESET.

In numbers:
- the 4S1P pack has learned a QMAX of about 3050mAh against a design voltage of 3000mAh.
- the FCC after a RESET is calculated at about 2800mAh (ok)
- the FCC calculated at wake up after SHUTDOWN is alwasy in the range 2100~2200mAh.

I have tried it with LOAD SELECT=7 (default) but also with LOAD SELECT=3, without any sensible difference.

This is quite weird and frustrating, beacause we ship the pack in SHUTDOWN mode and when the users reactivate the packs on first charge they will get incorrect and false perfecption that the pack is depleted

Do you know how to settle this ?

Regards
Pietro

  • 0
    TI__Mastermind 34775 points

    Hi Petro,

    Can you provide us with an srec and gg.csv file to review?

  • 0 in reply to Damian Lewis
    Intellectual 925 points

    Hello Damian,

    thank you for contacting me back.

    Please find here attached both srec and gg file.

    7411.bq40z50.zip

    I have made further investigations and found that I had: SUV-Mode=OFF in "Settings/Protectio/Protection Config."

    On setting SUV_Mode=ON, (with PF SUV Delay = 1sec) I realize that thre problem disappear on wake up after SHUTDOWN, while if I set SUV_MODE back to 0, the probem come back.

    It seems very consistent...

    What is exactly the cause of FCC  wrongly simulated ?

    Thanks in advance

    Pietro

  • 0 in reply to Pietro Vignali
    TI__Mastermind 34775 points

    Hi Pietro,

    On wake up the gauge runs simulation, if the cells are not rested prior to wake up (or BAT+ is shorted to PACK+ for waking up) the initial cell voltage used in the simulation could be incorrect leading to incorrect FCC/RSOC reporting. The SUV mode delay gives the cell voltage an additional 1 sec to settle before running simulation.