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BQ79731-Q1: BQ79718 Question

Part Number: BQ79731-Q1

Tool/software:

Hello,

I am using the BQ79718 AFE component, i have 15 cells and 2 bus bars between them. I saw that this AFE has just 1 BB pin for the bus bar measurement, is there a way to measure the both bus bars?

Thank you

  • Maor,

    You can have one bus bar attached to the BB pin and another occupying a channel. You can then measure the first one using the method described in section 7.3.3.1.1 of the datasheet and indirectly measure the second one by taking the BAT voltage measurement and subtracting all the other voltages (all cells + the first bus bar).

    Regards,

    Ben

  • Hi,

    Can you explain again how to calculate the second bus bar?

    Can i use 2 channels for the bus bars instead od BB? i mean cells 1-5 are real 5 cells, then cell 6 is the bus bar, then cell s 7-11 are real 5 more cells, then cell 12 is another bus bar, and then cell 13-17 are real more 5 cells?

    Thank you

  • Maor,

    You can put multiple bus bars in the cells like you described, as per section 7.3.3.3 of the datasheet. However, you will not be able to directly measure the voltage across the bus bar in this configuration, as the voltage is expected to be near zero. This is beyond the recommended operating conditions of the VC pins and prolonged exposure could damage the device. 

    You can indirectly measure the voltage of the bus bar when it is attached to the VC pins. The BAT voltage is typically the voltage difference between VC0 and VC18 and you can subtract out the voltages of the cells to get the bus bar voltage. If you have multiple bus bars, however, it will be unknown how much of the remaining voltage each bus bar is accountable for, so you must measure one using another method.

    Regards,

    Ben