Old NiCads behaving suspiciously: is this safe?
The 9.6V is the nominal voltage. 1.2V NiCad cells will charge to 1.45V when fully charged. This represents the 90~100% of charge. Under load, the cell will settle down to its 20~90% voltage, which for NiCad is the nominal 1.2V. So 8 series cells will charge past the 9.6V nominal of their combined cells. 12 Volts is about the highest voltage that you will see for that pack.