Rudi, DL2RM described his charger for nicad batteries in Sprat number 79. It incorporates a mains timer programmed as follows:
8 hours charge - 2 hours off - 2 hours charge - 2 hours off - 2 hours charge - 4 hours off - 2 hours charge
The idea is to prevent Nicads overheating towards the end of the charge.
Resistor R must be calculated from the formula:
Care should be taken to select R for the type of nicads being charged and it is noted in the article that this must not exceed 1A.