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Bq76PL536A

Sergio Espinoza
Prodigy 10 points

Hi all,

My question is regarding the Cell Balancing process, for both charging and discharging;( reference schematic "figure 18" on the "SLUSAD3" document).

Correct me if I am wrong, but based on the schematic this is my understanding on the cell balancing process;

When Charging - If a particular cell as reached the OCV the CBx pin is enabled for that cell which will by pass the charging current through the resistor that is connected in series with the transistor. Allowing for the other cells in the battery to continue charging.

When Discharging - if a particular cell as reach some deviation voltage threshold from the other cells, the CBx pins from the all  other cells are enabled which will discharge those particular cells at a faster rate, bringing all cells to within some margin of one another.

This is how I understand the cell balancing portion of the circuit. Feel free to correct me if am wrong. 

 

Thanks,

S 

  • 0
    TI__Genius 10785 points

    Hi Sergio,

    I think you got the right idea but not quite right.

    Cell balacing is to balace all cells. For example, if you have Vcell1 = 3.5V, Vcell2= 3.6V, Vcell3=3.5V, Vcell4=3.5V, Vcell5=3.5V and Vcell6=3.5V.  You are going to charge less current to Cell2  In Idle mode, you can bleed the Cell2.

    You can adjust the bypass current by selecting right R value.

    If you have 50 Ohm resistor then you are bypassing I=V/R. 3.6V/50R. I=72mA.  You can increase the current but you need make sure your components can handle the heat(W).

    If your charging current is 1A then you are charging 1A to all cell except Cell2. You are only charging 1A-72mA(.928A). You are turning on CBx for cell 2.

    You can balance the cells anytime and you don't need to wait until Cell voltage reaches OCV.

    In idle mode, you can turn on CBx (cell2) to bleed 72mA to bring down Vcell2 to 3.5V.

     

    Discharging mode: Concept is same as above. You want to balace the cell2 only.