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Can bq4050,bq40z60,bq40z50-R1 do cell balance independently

Siva Subramaniyam C N
Prodigy 140 points
Other Parts Discussed in Thread: BQ40Z60, BQ76920, BQ40Z50-R1, BQ4050, BQ78350-R1, BQ40Z50

I have 12V 20AH (3S,10P) Li-on Battery Pack and currently designing BMS with Cell Balance and Fuel Gauge Feature and like to know whether  bq4050, bq40z60, bq40z50-R1 can do cell balance independently because BQ76920(has cell balance feature but doesnt have algorithm/function in it,so it) requires BQ78350-R1(which has algorithm/function for cell balance).

So i like to know whether  bq4050,bq40z60,bq40z50-R1 has cell balance structure and algorithm/function in it.

  • 0
    TI__Mastermind 25955 points
    Hi Siva,

    Cell balancing in the bq4050 device is accomplished by connecting an external parallel bypass load to each cell of the associated AFE, and enabling the bypass load depending on each cell's charge state. The bypass load is typically formed by a P-CH MOSFET and a resistor connected in series across each battery cell. The filter resistors that connect the cell tabs to VC1~VC15 pins of the associated AFE are required to be 1 kΩ. Using this circuit, the bq4050 balances the cells during charge by enabling the bypass around those cells above the threshold set in Cell Balance Threshold if the maximum difference in cell voltages exceeds the value programmed in Cell Balance Min. During cell balancing, the bq4050 measures the cell voltages at an interval set in Cell Balance Interval. The cell(s) to be balanced are prioritized by highest cell voltage but the bq4050 will not try to balance adjacent cells. If adjacent cells need to be balanced, the bq4050 will alternate between the highest and next-highest adjacent cells until they are balanced. On the basis of the cell voltages, the bq4050 either selects the appropriate cell to discharge or adjusts the cell balance threshold up by the value programmed in Cell Balance Window when all cells exceed the cell balance threshold or the highest cell exceeds the cell balance threshold by the cell balance window. More in-depth details and data on this cell balancing algorithm can be found in: http://www.ti.com/lit/slva155.

    The bq40z50/__/-R1/-R2 can determine the chemical state-of-charge of each cell using the Impedance Track algorithm. The cell balancing algorithm used in the device decreases the differences in imbalanced cells in a fully charged state gradually, which prevents fully charged cells from becoming overcharged, causing excessive degradation. This increases overall pack energy by preventing premature charge termination. The algorithm determines the amount of charge needed to fully charge each cell. There is a bypass FET in parallel with each cell connected to the gas gauge. The FET is enabled for each cell with a charge greater than the lowest charged cell to reduce charge current through those cells. Each FET is enabled for a precalculated time as calculated by the cell balancing algorithm. For more information please refer to Section 13.5.12 of the TRM found at www.ti.com/.../bq40z50.pdf , www.ti.com/.../bq40z50-r1.pdf , and/or www.ti.com/.../bq40z50-r2.pdf

    Sincerely,
    Bryan Kahler