On Wed, 16 Jun 2004 10:34:33 -0400, Glenn Ashmore
wrote:

NiCads develop a memory over time and can't be fully recharged unless
they are fully discharged occasionally.

This is (almost) a myth. The Ni-Cad memory phenomenon
does exist, but I can almost promise that no-one
reading this has ever experienced it. It requires
that the partial discharge/charge cycle be repeated
*****EXACTLY***** many, many times. It was discovered
in a satellite (and eventually duplicated) where the
battery discharged for a precise length of time into
a precise load, and then was recharged for a precise
length of time at a precise rate. When the program
of the satellite was changed later, it was found that
the battery could not continue providing power after
passing the previous discharge point.

It simply won't happen just because you don't run
a Ni-Cad down to zero before recharging it. In
fact if you DO run it to zero, there is a very good
chance that (because of slight differences in cell
capacity) that you will reverse-charge one or more
of the cells, which WILL ruin that cell quickly.
Better to get it onto the recharger as soon as
you experience a significant drop in output
under load. At the point where your battery drill
stalls at no load or very light load, you may well
be pumping up one of the cells backwards as the
other cells push the last few electrons through
the load.

The commonest way to damage Ni-cads, however, is to
leave them on the charger too long, or to charge
them too fast at some point in the recharge cycle.
Every time this happens, the battery will lose
some of it's capacity.