It can be read from HConfig2.BAL to see if balancing is indeed active. If HConfig2.BAL is non-zero, then balancing is active.
The value of the BAL bits differs depending on the number of cells.
For 4S Configuration
BAL=000 : Balancing off.
BAL=001 : CELL1 balanced.
BAL=010 : CELL2 balanced.
BAL=011 : CELL3 balanced.
BAL=100 : CELL4 balanced.
For 3S Configuration
BAL=000 : Balancing off.
BAL=001 : CELL1 balanced.
BAL=011 : CELL2 balanced.
BAL=100 : CELL3 balanced.
For 2S Configuration
BAL=000 : Balancing off.
BAL=001 : CELL1 balanced.
BAL=100 : CELL2 balanced.