SLUUCH2 March 2021 BQ40Z50-R2
The BQ40Z50-R4 enables voltage based cell balancing if Settings:Balancing Configuration [CBV] = 1, and balances the cells by enabling the bypass around those cells above the threshold set in Voltage Cell Balance Threshold if the maximum difference in cell voltages exceeds the value programmed in Voltage Cell Balance Min. During cell balancing, the BQ40Z50-R4 measures the cell voltages at an interval set in Voltage Cell Balance Interval.
The cell(s) to be balanced are prioritized by highest cell voltage but the BQ40Z50-R4 will not try to balance adjacent cells. If adjacent cells need to be balanced, the BQ40Z50-R4 will alternate between the highest and next-highest adjacent cells until they are balanced.
On the basis of the cell voltages, the BQ40Z50-R4 either selects the appropriate cell to discharge or adjusts the cell balance threshold up by the value programmed in Voltage 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.
Cell balancing occurs when charging current is detected or in rest if enabled, and on non-adjacent cells at the same time. The cell balance threshold is reset to the value in Voltage Cell Balance Threshold at the start of every charge and reset cycle. The threshold is only adjusted once during any balance interval.
The configuration data flash is stored in Advanced Charging Algorithms: Cell Balancing Config. The starting and rest conditions for voltage based balancing are same as state-of-charge based cell balancing.