On Mon, 30 Jan 2006, Greg Copeland wrote:

Be careful when switching to alternate battery technologies. NiCads are
designed to be charged at rates up to 3C while most NiMH are
typically designed to be charged no faster than 1 to 1.2C.

Can you back this up with some documentation? I'm not an expert, just a
relatively well informed user, but this runs counter to everything I've
read. The rule of thumb for most common battery chemistries is C/10 (1/10
the amp-hour rating) for 12 hours. As far as I'm aware there's no way to
safely (that is, without damaging the cells) speed that up significantly
without microprocessor controlled chargers and special waveforms. Even
with those things I doubt it's possible to charge NiCd's or NiMH's
anywhere near as fast as you suggest (20 min. to 1 hour) without severely
shortening their lifespan. Take care of your batteries, and you might
actually get the 1000 charges the manufacturers advertise; abuse them, and
you might get only a dozen or so charges.

In short, get an extra set or two of batteries, charge them slowly, don't
ever overcharge them, and they'll live a lot longer.

Long of the short, if you change battery technologies, make sure you
change chargers too! Otherwise, you may be in for a surprise including
very short battery life, batteries which never hold a full charge, and
maybe even fires.

To the contrary, all information I've ever come across indicates the
charge cycles are identical for NiCd and NiMH. In other words, they're
completely interchangeable, assuming of course that one accounts for the
different capacity when charging. NiCd's are lower capacity (usually
_much_ lower), so generally, NiMH's can be safely charged in chargers
designed for NiCd, but the reverse isn't necessarily true.

For some years I've been using NiMH's in cordless phones designed for
NiCd's, with absolutely no problems. Battery life between charges is much
longer with NiMH's, and lifespan is also much greater because of NiCd's
memory effect.

-Dan