BQ27Z561-R1: Delay time for VCT is less than 80s

Hello,

I use BQ27Z561-R1 for the valid charge termination condition of the delay time for VCT is 2*40s =80S,We find it is less than 80s,what the reason?

I set taper current=280mA,Charge Term Voltage Offset=45mV,Standard Temp High Charging Voltage=4530mV,when voltage≥4485mV,Average current＜280mA,it takes only 55s then it triggers VCT.