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BQ76952: Cell balancing of cell 16 is not happening

Mohammed Suffiyan
Intellectual 461 points
Part Number: BQ76952

Hi team,

I am using BQ76952 BMS IC. I have opted for external cell balancing and the system is working as expected. While verifying the system, I found out that cell 16 is not getting balanced but it is showing high in cell balancing active cells register (8AAA {hex} - 1000 1010 1010 1010 {decimal}).  When I measure voltage across external resistor of cell 16 it is 0V; but when I measure voltage across 2,4,6,8,10 and 12 it is 3.8V and it is working as per design which is 150 mA. The configuration setting is max 8 cells can be balanced. Start delta relax is 10 mV and stop delta relax is 5 mV. Please assist me in resolving this issue.

  • 0
    TI__Mastermind 27321 points

    Hello Mohammed,

    Is Cell-16 the most discharged cell? Can you show the voltage reading of all cells? It could be that cell-16 is the most discharged cell and it does not balance, instead, other cells will balance down to cell-16.

    Have you tried cell balancing only on cell-16? If so, do you see the same behavior? If you try this, make sure other cells show lower voltage.

    Please share your schematic.

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    Intellectual 461 points


    Cell 16 has the highest voltage of all, so it has to discharge and get back to lower voltage. 

    How to test cell balancing on cell 16 only?

  • 0 in reply to Mohammed Suffiyan
    TI__Mastermind 27321 points

    Hello Mohammed,

    Mohammed Suffiyan said:
    How to test cell balancing on cell 16 only?

    Try host controlled for a specific cell (cell-16),Try this sequence:
    W    : 10 3E 83 00 00 80
    W: 10 60 FC 06

    Note: The command will have to be re-sent after 20 seconds. It has a timer where cell balancing stops automatically. Make sure Settings: Cell Balancing Config: Balancing Configuration: [CB_NO_CMD] is zero (this will allow host control).

    Measure the voltage across Rbal (R5) and also across VC16-15 pin of the FAE. The voltage will drop across the VCx pin if cell balancing is active.

    Are you using real cells or a cell simulator? 

    Regards,
    Jose Couso