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BQ40Z50-R1: RSOC discrepancy

Matthieu Imbert
Intellectual 820 points
Part Number: BQ40Z50-R1
Other Parts Discussed in Thread: BQSTUDIO, BQ40Z50

Hello,

Something strange happened to the gauge in one of our 256Wh LiFe 4S6P (12.8V 20Ah) smart battery from China.

Our customer had rented it, and all of a sudden, the battery reported RSOC = 0% on his (our) SMBus power station.

And indeed, back in our workshop, bqStudio reports RSOC = 0%. The strange fact is that the onboard led display (25% steps) does show the correct value : the battery RSOC is above 75%.

And actually the battery passed  more than 16Ah befor the pack reached 11V, somewhere close to 80% of design capacity.

SMBus is OK, as bqstudio collects all the other data, and all commands do work fine. So the chip is not totally out of order.

Has someone got an idea of what's going on? How can we get the RSOC to be correctly  polled via SMBus? And how come the leds display correct RSOC value, but not the SMBus?

Thanks for your help.

Regards.
Matthieu

  • 0
    Intellectual 820 points

    Hello again,

    Switching IT (GAUGE_EN) OFF then ON turned RSOC "alive": it jumped from 0% to 3%.

    And it keeps increasing as battery is charging.

    Is that a clue?

    Thanks.

    Regards.
    Matthieu

  • 0 in reply to Matthieu Imbert
    TI__Mastermind 19195 points

    Hi Matthieu,

    1. Has the correct chemID been programmed
    2. Has a learning cycle been completed?

    Thanks,

  • 0 in reply to Nick Brylski
    Intellectual 820 points

    Hello Nick,

    Yes, ChemID has been programmed (04XX), learning cycle has been made.

    It has been performing 20 cycles only, and the customer told us it happened all of a sudden.

    This pack is part of a 10 units batch, all other nine running without any problem.

    As written here above, by toggling Gauging (IT_EN) off and back on after a full discharge made the RSOC jump from 0% to 3%.

    Now the pack is still charging, and everything seems OK as far as RSOC is concerned.

    But still:

    how do you explain the onboard RSOC led display is OK, but the SMBus RSOC reading returns 0%?

    I think the issue is not in gauge programming (.srec etc), but hardware related: the host cannot "read" file at address 0x0D. But bq40z50 engine can, thus led display is OK.

    Thank you

  • 0 in reply to Matthieu Imbert
    TI__Mastermind 19195 points

    Hi Matthieu,

    The LEDs and the SMBUS will pull RSOC from the same register.

    Can you upload the .gg and I will try to replicate this.

    Thanks,