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BQ76972: Need support for Configuration Review.

Vamsi Tungala
Prodigy 55 points
Part Number: BQ76972
Other Parts Discussed in Thread: BQ76952EVM, BQSTUDIO

Tool/software:

HI 

I am developing a Charger for 48v battery along with Balancer IC BQ79672. Charger is working as expected but the Balancer is not doing the balancing even when the voltages are above the threshold values. I have attached the csv file for reference. 
I disabled all the protections to check the basic functionalities.


Thank you

test3.gg.csv

  • 0
    TI__Mastermind 42060 points

    Hello Vamsi,

    Check you temperature pins, ensure they are all within balancing ranges, in what conditions are you trying to balance?

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 55 points

    Hi Luis

    Thank you for the reply. Currently we bought BQ76952EVM Board for testing purpose. In that i configured the Cell balancing bits as per the image. After the configuration, the balancing status changed. I waited for two hours but it only reduced 6mv. Is it supposed to be this much slow? 
    i am using 12 cell configuration. Are there any settings to increase the charging speed.

  • 0 in reply to Vamsi Tungala
    Prodigy 55 points

    Hi 

    I tested with smaller battery pack and it is balancing but very slow because i am using internal FETS. The 12s battery pack was too big for internal FETS to see any difference in balancing.

    Now i am trying to integrate external FETS for faster balancing along with EVM. when i added external FETS the voltage readings of each cell are soo fluctuating. when it is trying to balance, It is turning on the balancing over the lowest cell too and it keeps decreasing and continuous to drain the battery.

    Can you tell me what might be the issue here?

    Thank you.

  • 0 in reply to Vamsi Tungala
    TI__Mastermind 42060 points

    Hello Vamsi,

    Can you shared your schematic and a log of what is happening?

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 55 points

    Hi 


    I am trying to connect external FETS to EVM board to decrease the balancing time. when i connect the FETS, voltage readings are fluctuating up and down. when i start balancing, the IC tries to balance lowest cell as well which makes it to reduce more. this process is continuously going on and the battery is draining. i attached the FET schematic and the Log from BQstudio. I am connecting the EVM BAT-, C1, C2, C3,C4 to VC0,VC1, VC2,VC3,VC4 in the schematic. and i removed the capacitors in my schematics as they already present on the EVM Board. 
    (Note: Please ignore the FETs Direction they are wrong in the schematic.)
    Please let me know if you need anything else.

    Thank you for your help. 


     7774.log.txt

  • 0 in reply to Vamsi Tungala
    TI__Mastermind 42060 points

    Hello Vamsi,

    I see you are not using VC16 - VC15. It is very important this connection is used with a real cell because it powers the internal balancing circuitry. I'd advice to test again with a cell attached to VC16 - VC15.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 55 points

    Hi 

    I tested with a cell in between VC15 and  VC16.and the results are same as before, voltages readings are fluctuating and the balancing is continuously discharging all batteries. sometimes when the voltages are under the stop delta range it stopped for few seconds and again there was some voltage fluctuation and again started balancing. is there a way to eliminate this voltage fluctuations?