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BQ40Z50-R1: How to confirm the cell balancing

Naveen Bevara
Intellectual 1970 points
Part Number: BQ40Z50-R1

Hi, 

How to confirm from log file of BQ40Z50-R1 that cell balancing is done? (Internal cell balancing is used) 

Does the pack need to be in relax state for cell balancing to happen? Or does the device update the balancing parameters in relax state and cell balancing is done whenever RSOC>(Min RSOC for Balancing) and difference between battery voltages > (Min Start Balance Delta)?

  • 0
    TI__Intellectual 1840 points
    Hi,

    Reading the TRM, it is indicated in page 92, of the PFAlert() flags of ManufacturerAccess() 0x0052, if the CB bit (Bit 8) = 1, then Cell Balancing Failure was detected, if CB bit = 0, then a failure was not detected. You can find the TRM here: www.ti.com/.../sluubc1c.pdf

    The cell needs to be in a relaxed state for the gauge to determine whether it needs balancing or not. Take a look at the reference manual, Chapter 7: Cell Balancing, page 55.

    Hope this helps,
  • 0 in reply to Nabil M
    TI__Intellectual 1970 points

    Hi Nabil, 

    Thanks for the reply. The customer says that the pack may not be in relax state for most of the time. If the gauge once determines whether to balance it or not, does it continue to do until next relax state?  

  • 0 in reply to Nabil M
    Intellectual 640 points

    Hi Nabil,

            Presently we are using only the internal cell balancing feature of bq40z50-R1. Page 55 in the TRM says  "When any bypass FET is turned on, then the OperationStatus()[CB] operation status flag is set". I can see that during the charging phase, this CB bit gets set. Other than the status of this flag, is there any other way to really see that cell balancing is happening ?

  • 0 in reply to Venugopal S
    TI__Intellectual 1840 points
    Well internal cell balancing does take a little more time. I'm not too familiar with this part, but it seems that this CB bit is the only way to indicate if cell balancing is happening or not. If you read through chapter 7, it will give you an idea of how the gauge decides when to start balancing, based on it's condition (charge, discharge, relax etc.) and the thresholds and parameters you set.

    Other than monitoring these status bit/flags, I don't see any other way of checking.