http://www.powerstream.com/NiCd.htm

The cheapest way to charge a nickel cadmium battery is to charge at C/10 (10% of the rated capacity per hour) for 16 hours.. So a 100 mAH battery would be charged at 10 mA for 16 hours. This method does not require an end-of-charge sensor and ensures a full charge.

If a temperature or voltage monitor is used (!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!) NiCad batteries can be charged at rates up to 1C