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Original question:

BQ76952: Turning OFF PCHG & PDSG FET's turns off Main FET's

BQ76952: Battery Pack entering in to Shutdown mode

Naga Penmetsa
Prodigy 60 points
Part Number: BQ76952

Hello,

We are using Bq7695202 in a battery management system for a 16S configuration battery pack.

1) We have observed that when the total pack voltage is around 40V.  The AFE is entertaining in to Shutdown mode and the AFE stops responding to I2C commands ( data read).  As soon as  we pull the TS2 pin low, the AFE starts working again and responds to I2C data read correctly. The only configuration we set in the Power configuration registers is to enter in to Shutdown mode when the pack voltage is 38V, all other configs are at default values. What puzzles us is that why the AFE is going in to Shutdown mode when the pack voltage is well above 38V (little above 41V, AFE is also reading 41V). 

One note is that one of the cell is slightly imbalanced and 2.42V (we set the CUV at 2.53V). Is there any relation to CUV and shutdown mode ??

2) Another issue we are facing when one of the cell voltage is at 2.42 (CUV set at 2.53). We are not getting the Alert pin change its state when we configured the CUV to assert Alert pin. Even the Alarm SSA register value is reading Zero.

Any help would be highly appreciated.

Thanks,

Naga Penmetsa

  • 0
    TI__Mastermind 27321 points

    Hello Naga,

    1- CUV is not related to shutdown.

    Shutdown should happen if:
    a- stack voltage < Power:Shutdown:Shutdown Stack Voltage
    b- lowest cell voltage < Power:Shutdown: Shutdown Cell Voltage
    c- temperature > Power:Shutdown:Shutdown Temperature
    d- shutdown command is sent

    Please send your configuration by exporting the gg file to check your settings.

    2- Did you enable CUV in Settings: Alarm: SF Alert Mask A? Please share your configurations.

    To debug this, you should be monitoring bit 12 in the three below highlighted registers. 



    Note: The Alarm Status register is a mask with Alarm Enable. So even if CUV happens, if it's not enabled, it will get ignored.

    Regards,
    Jose Couso