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Original question:

BQ76952: Cell Balance Max Cells of BQ76952

BQ76952: Cell balancing can be balanced simultaneously

Duc Nguyen
Prodigy 21 points
Part Number: BQ76952

Hi expert!


I have a question about cell balancing.

My BMS uses 16 cells, and I want 8 cells to be balanced simultaneously. When I send subcommand to active 1 cell balancing, the device work very well. But when I send subcommand to active 2 or more cells (non-adjacent), CUV or COV alert is detected at the 1-sec check, balancing is immediately disabled. How can I avoid CUV/COV alert while balancing is active and cells can be balanced simultaneously. 


Please give me some advice to resolve the problem!

Thanks and Regards

Duc Nguyen

  • +1
    TI__Guru* 81034 points

    Hi Duc,

    Do you have cells connected to the board when you see this issue? Or are you using a resistor divider for this test?

    During balancing, the BQ76952 disables CUV/COV temporarily and every 1 s, it stops balancing to check COV and CUV. Can you share your balancing circuit? Maybe the settling time for the voltages is long.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 21 points

    Hi Matt,

    I am using a 16 resistor divider for this test with the value of the resistor is 1k Ohm, and power supply is 60V. Because I have a new battery pack and it has no cells need balance. I want the test device to operate with function cell balancing for this test.

    Here is my schematic: BQ76952_sheet

    Maybe the situation I have simulate not exactly like in reality. It makes the device operate not correctly. I will check it.

    Thanks and Regards

    Duc 

  • +1 in reply to Duc Nguyen
    TI__Guru* 81034 points

    Hi Duc,

    With a resistor divider, when one cell starts balancing, it pulls current from the resistor string so it will affect all of the cell voltages up and down the entire stack. To test balancing, you need to use real cells or a stack of voltage sources that can maintain a fixed voltage even when balancing current is flowing in/out of them.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 21 points

    Thank you for all your support!