What voltage to charge a single NiCd cell?
NiCD has the benefit of a higher resistance when charging comes up to 1.2 V per cell.
This voltage has to be respected.
If you can control the charging current try charging 10 cells at 200 mA and give it a go. Then, voltage will be spread over the cells evenly (the lower-charged cells will pull the voltage to their level until they match the next cell which will start charging along.)
They can be charged at several different rates, depending on how the cell was manufactured. Refer to the datasheet from the supplier.