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BQ76930: How to BQ76930 implement open wire detection?

john xiao
Intellectual 470 points
Part Number: BQ76930

Dear all:

I find the BQ76930 no open wire detection function.but this function is very important.please tell me how to implement open wire detection?Thank a lot.

  • 0
    TI__Guru 54715 points
    Hi John,
    You could turn on cell balancing, it will come on at the next scheduler interval. During balancing the part multiplexes measuring and balancing, if the input is disconnected the voltage will not recover for measurement and you will see an unusual voltage. Note that an open wire with balancing on may pull the input to a level which could exceed abs max.
    Select an algorithm which steps through the inputs avoiding adjacent cells as noted in the data sheet.
    Be sure to turn off balancing after your test.
  • 0 in reply to WM5295
    Intellectual 470 points
    Hi WM:
    I turn off the cell balance when the rest and discharge period. when some cells(as cell2,3,4,7,8,9)open wire,the voltage fall slowly. there is no immediate imbalance.I desire once open wire, detect it immediately.Please make better proposals.
    if I reduce the capacitance between VCn and VCn–1 to 0.1uF,is it ok?
  • 0 in reply to john xiao
    TI__Guru 54715 points
    Hi John,
    You could build a constant current source on each input and turn them on as desired. Remember that the bq76930 takes 250 ms to measure all cells.
    Yes 0.1 uF is ok, the filter cutoff will be higher but it will settle faster for less voltage disturbance during balance.
  • 0 in reply to WM5295
    Intellectual 470 points

    Hi VM:

    How to build a constant current source on each input,Please provide a reference circuit.thanks a lot.

  • 0 in reply to john xiao
    TI__Guru 54715 points
    Hi John,
    Please consult your favorite engineering references and select a circuit topology which meets your needs.