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Original question:

BQ78350-DEVICE-FW: Cell Balancing at Rest Test

BQ78350-DEVICE-FW: R3: Cell Balancing At Rest

Steven Phan
Prodigy 10 points
Part Number: BQ78350-DEVICE-FW
Other Parts Discussed in Thread: BQSTUDIO, BQ78350

Hello,

We are having a hard time getting the cell balancing at rest feature on the new BQ78350-R3 FW to work on our battery pack system. We noticed that cell balancing while charging is working as expected; however cell balancing at rest is not. We determined if cell balancing was working properly based on the state of the "CB" bit in the "Operation Status" register in BQStudio.

From our understanding this is a new feature that is implemented by TI on the BQ78350-R3 firmware from https://www.ti.com/tool/BQ78350-DEVICE-FW and that one way to enable the feature is to enable the "CB_REST" bit as well as the "CB" bit in the balancing configuration register section of data flash. Furthermore, our understanding is that the current measured by the TI AFE needs to be less than the "Quit Current" written in data flash in order for the BMS to be in a relaxed state and start balancing. Additionally, all of the cell balancing criteria must be met, which are the same as the previous version of FW on the chip where cell balancing is only active during charge.

Could we get some advice on what we may be doing wrong or advice on what else we can provide for diagnosis? I have attached our gg.csv below as well as configuration information from BQStudio

BQ78350-R3.gg.csv

Confirmed TI FW Version is R3

Cell Balancing Configuration

Balancing Configuration Register

Cell Balance bit in Operation Status not set

Thanks in advance for your help

BQ78350-R3.gg.csv

  • 0
    TI__Mastermind 25136 points

    Hello Steven,

    I think your understanding is correct. Can you check if the CB_TEST bit in the ManufacturingStatus() register gets set when Cell Balancing conditions are met?

    Please reference to this document for more details of the added feature.

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    Prodigy 10 points

    Hi Jose,

    Thanks for getting back so quick! From the last screen shot, the CB_TEST bit from the ManufacturingStatus() register was not set either when the pack was relaxed and cell balancing conditions were met

    Best,

    Steven

  • 0 in reply to Steven Phan
    TI__Mastermind 25136 points

    Hi Steven,

    Can you read what the firmware build version is? In build 31, it was added a read/write command to enable or disable the cell balancing at Rest operation,
    and to read back status of cell balancing at Rest operation.

    For CB to work in relax, the CB_TEST_EN needs to be set in Manufacturer Status register. Please set bit13. See below



    Please let me know if this helps.

    Regards,
    Jose Couso