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BQ4050: bq4050 cell balancing algorithm and conditions

Alexander Strokanov
Intellectual 450 points
Part Number: BQ4050

Hello!

Cant make bq4050 cell balancing ability to work. I want CB to starts form 3300 per cell, so CB settings is:

Cell Balance Threshold 3300 mv

Cell Balance WindowMin  900 mv

Cell Balance Min  20 mv

Cell Balance Interval 20 s

Cell balancing configuration register is "01"

Then I set charging current form between 100 mA and 4000 mA, then BAL_EN sets to "1" but CB is "0".

Cell voltages during charge is:

cell 1: 3884

cell 2: 3849

cell 3: 3846

cell 4: 3851

I tried to make CB work with various settings, but nothing came of it. years of the project in the attachment.

balance_test_4050.gg.csv

  • 0
    TI__Mastermind 42535 points

    Hi Alexander,

    Please leave your cell balance Window at 100. With 900 you are exceeding the window space. Then reset and run your test again.

  • 0 in reply to Batt
    Intellectual 450 points

    Hello!

    But I tested that settings before, and still cant understand how algorithm works((

    Now I set:

    Cell Balance Threshold 3400 mv

    Cell Balance WindowMin  100 mv

    Cell Balance Min  10 mv

    Cell Balance Interval 25 s

    (Cell_1 should be balanced)

    Reset controller and.. and after approx 1-2 minutes CB sets to "01" on Cell_1. Its ok becouse cell_1 is higher then others more then 30mv (30-60, or more, depends of current) .

    Then I reset controller with same current. And CB starts again after 1-2 min but on the Cell_2...But Cell_2  is lower then Cell_1.

    Then I reset controller again, same current - CB starts again after 1-2 min... on The Call_2 and Cell_3 simultaneously (???) although the Cell_2 and Cell_3 are both lower then Cell_1.

    Then I reset controller several times with same settings and same current on charge, sometimes CB didnt started at all till reset, sometimes starts at sought-for cell_1, sometimes strats at cell_2 that should not be balanced.

    Now I still don’t understand what settings should be in the order for the cell that is charged the most to be balanced, when it should be happen.

  • 0 in reply to Alexander Strokanov
    Intellectual 450 points

    upd: CB starts stable after a about minute, but for this, I manually make cell disbalance over 150 mv in delta (150-170 depends of current).

    So the CB algorithm is still not transparent to me, what is the “Cell Balance Window”?

  • 0 in reply to Alexander Strokanov
    TI__Mastermind 42535 points

    Please refer to the TRM, SLUUAQ3, chapter 7, for what each of the parameters does. This is a CEDV gauge and does voltage based balancing. The thresholds are to simply determine the voltage deltas at which balancing starts and ends.

     also explains cell balancing in detail.