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BQ76920: Missing Cell readings for 4 cells pack

Andrew G
Prodigy 10 points
Part Number: BQ76920


Hi, this is my first BMS design project and I am having some issues with the voltage readings. I am able to get readings for Cell 1 to Cell 3 and pack voltage. But cell 4 is missing reading. This BMS is designed for 4 cells LFP battery pack. 

I am not using the current sensing function for this project, so the IC is mainly for voltage sensing and passive balancing.

Although my schematics have external FET for cell balancing, it is not used, thus the 0R jumpers were already removed.

Any help is greatly appreciated!

  • 0
    TI__Mastermind 42060 points

    Hello Andrew, 

    Did you measure the voltages at the pins to ensure the right voltage is reaching the correct pins?

    Can you highlight which components are not placed and which are placed?

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 10 points

    Hi Luis,

    Thank you for your reply. Below is the updated schematic with the red cross indicating the components which isnt placed. The battery pack is being connected to connector "TO_BAT_MODULE_(ICB)". External FET cell balancing is not used at this point in time.

    Regards,

    Andrew

  • 0 in reply to Andrew G
    TI__Mastermind 42060 points

    Hello Andrew,

    Do the voltages read correctly at the input pins? I do not see why it would not measure correctly unless things are not connected properly.

    Have you tried changing the IC itself?

    Best Regards,

    Luis Hernandez Salomon