NiCad batteries and the memory effect

[Larry Smith <Larry.Smith@SNOW.EDU>]

I've been told that deep discharging reduces the memory effect of NiCad
rechargeable batteries; however the new rechargeable million-candle-power
spotlight we just bought says _not_ to deep discharge it, and that the
battery will last many more cycles if it is recharged immediately after
shallow use.

Questions:
1. What causes the memory effect in the first place?
2. Why does deep discharging reduce the memory effect?
3. Why does Lectro-Sci (maker of the Night Tracker spotlight) say not to
deep discharge their NiCads?

Thanks in advance,
Larry Smith