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Original question:

[FAQ] BQ76952: Is the BQ769x2 able to do gauging? Can it calculate and report SOC and SOH?

BQ76952: BQ76952

John DeCesare
Intellectual 290 points
Part Number: BQ76952
Other Parts Discussed in Thread: BQ7718, BQ77216, BQ34Z100-R2, BQ78350-R1A, BQ34Z100

I noticed in the BQ76952, there is built in cell over/under voltage Protection. But on the Eval board, there are separate BQ771807 cell over/under protection devices. This seems redundant.  But it seems as of the BQ771807 autonomously asserts the Fuse (if installed) as well as the Red LED.  If not using the Fuse, then it really only turns on the RED LED.  From reading the data sheet of the BQ76952, it seems as if I can configure each cell COV and CUV levels and have them interrupt using the Alert pin.

What is TI's recommendation for using the BQ771807?

I also read in the forums that the BQ76952 does not support gauging but it does have a coulomb counter.  I was assuming the coulomb counter will provide capacity of the battery based on current flow via the sense resistor.  Is this a correct assumption?

Thanks!

  • 0
    TI__Mastermind 39120 points

    Hello John,

    You are absolutely correct, it is redundant. This is typically what a secondary protector does, it provides redundant protections separate from the main AFE. The reason why we show this, is because many customer's standards require separate protection for certain aspects (Such as COV), that are separate from the main AFE and/or hardware-based only. This is why we show it on the schematic, however, it is not required and as you said ,you can use solely the BQ76952. 

    The BQ76952 is also able to detect secondary protector triggers through its FUSE pin, if a secondary protector trigger it would drive the BQ76952's FUSE pin high.

    There are many types of secondary protections, like the BQ7718 you pointed and the BQ77216, which is a 16s secondary protector.

    John DeCesare said:
    I also read in the forums that the BQ76952 does not support gauging but it does have a coulomb counter.  I was assuming the coulomb counter will provide capacity of the battery based on current flow via the sense resistor.  Is this a correct assumption?

    Not quite. Yes, the BQ76952 provides a coulomb counter, so it measures the accumulated charge over a period of time. However, the gauging algorithm itself has to be done by the host-side. The part does not provide battery capacity/health.

    Hope this helped answer your questions!

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Intellectual 290 points

    Hi Kuis,

    Could not have asked for a better answer and so quickly.  Much appreciated. Do you have a suggestion for a gauge?  The battery pack could be close to 300Ah.

    Thanks again!

    John

  • 0 in reply to John DeCesare
    TI__Mastermind 39120 points

    Hello John,

    No problem!

    If you want gauging with the BQ76952, then I would recommend the BQ34Z100-R2. This is a top-of-stack gauge, so it provides gauging based on the overall stack, not individual cells.

    Other gauges can only provide gauging for up-to 6 cells in series.

    If you have more questions on the gauges, I'd recommend to open a new thread so that the gauging team can help you Slight smile.

     Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Intellectual 290 points

    Hi Luis,

    I will take your advice and post to the gauging team but the AFE and Gauges seem to be so intertwined, I don't know what the best forum is.  So I will ask both.

    I looked at the Bq78350-R1A  gauge and it seemed to be a better fit in terms of capacity 320Ah vs 7000Ah but the part seemed to be more geared to the BQ769x2 family of AFEs. My battery stacks will vary from 4 to 10 to 14 so I liked the BQ76952 since it seems to handle different stack sizes and therefore one PCB with different SKUs.  The BQ769x2 has different packages for each cell stack so therefore I would need three different PCB's which is not optimal.

    Looking at the BQ78350-R1A datasheet, it seems like the gauge talks directly to the BQ769x0 via I2C and my processor will talk SMB to the gauge. It seems like a very simple and self contained system which is nice.

    Looking at the datasheet for the BQ34Z100-R2, it seems to have it's own Coulomb counter. Are there reference designs using the BQ76952 and the BQ34Z100-R2?

    Thanks!

    John

  • 0 in reply to John DeCesare
    TI__Mastermind 39120 points

    Hello John,

    As long as you put a gauge as a part and in the title during the thread creation, it should point to the appropriate team!

    The BQ78350-R1A is actually the companion gauge for the BQ769x0 family (Which is an older monitor generation), not for the BQ769x2 family. The BQ78350-R1A also uses the CEDV gauging algorithm, instead of the Impedance Track algorithm that the BQ34Z100-R2 uses. 

    Unfortunately, at the moment you'd need the BQ34Z100-R2 if you want a gauging algorithm with the BQ769x2.

    Looking at the datasheet for the BQ34Z100-R2, it seems to have it's own Coulomb counter. Are there reference designs using the BQ76952 and the BQ34Z100-R2?
    Yes, it has its own gauging algorithm, so you'd need to use separate filter components to the sense resistor (to the filter components of the BQ76952). There is a reference design in development using both the BQ76952 and BQ34Z100, but there is no estimated release date for it.

    Best Regards,

    Luis Hernandez Salomon