When doing a 2C discharge with a 4S Li-Ion pack the voltage drops to my Discharge Completion (DC) voltage, 11600mV, and the DFET turns off after the Discharge Completion Time (2sec) and Discharge Completion FET Activation Time (2sec) have elapsed. It then stays off after this point. So far, so good.
When doing a 7.5C discharge, the pack reaches the DC voltage, the two timers elapse and the DFET turns off. After a fraction of a second to several seconds, the DFET turns back on and the pack starts discharging again until the DC voltage is reached. The DFET turns off again, etc. This repeats until the PUV or CUV point is reached where, finally, the DFET stays off (I have the recovery voltages set pretty high for PUV and CUV).
What could be causing this?
At first I thought the problem might have been related to a particular timer or rebound voltage level but a read of the Tech Manual seems to indicate that there's no timer or voltage affecting the clearing of the DC bit. Just a charge current or the discharge current essentially stopping before the Discharge Completion FET Activation Time timer elapses. But, I successfully reach the DC point and the DFET turns off so the timers shouldn't matter.
I've attached two screen captures. The first shows the 7.5C discharge and how the DFET keeps turning back on. The second shows a 2C discharge done right after the 7.5C discharge reached the DC voltage. Both discharge current levels show the DFET turning back on after different voltage and timer intervals.
Since the rebound voltage level, and rate of increase, is much higher after a 7.5C discharge reaches the DC voltage level, could this somehow be the cause? This is the only difference I can think of between the 2C discharge (all the way from 100% SOC to the DC voltage) and the 2C discharge I did immediately after the 7.5C discharge reached the DC voltage.
