My NiCad battery gave up the ghost in my HT for the second time. They only
seem to last a few years, at the most.

Not uncommon. NiCd batteries _can_ have a fairly long service life
(up to 1000 charge/discharge cycles) if treated gently.

Unfortunately, in many applications they aren't treated gently...
they're run down all the way to zero (which tends to reverse-polarize
the weakest cells and damage them), and are recharged too rapidly
without proper charge management.

Even when treated very well, 1000 charge/discharge cycles wouldn't
last you more than 3 years if you run 'em down fairly far every
day, and recharge every night.

I was wondering if I replace the
NiCad's with newer NMHi batteries can I use the same charger? Both type
batteries are about 1.2 volts when charged. But I'm not sure about their
charging requirements.

In general, I believe that the answer is "maybe".

NiMH batteries can usually be trickle-charged using the same basic
method used for NiCd batteries. If your HT and its charger normally
required somewhere between 10 and 16 hours to fully recharge your
existing battery pack, then it'd probably work well enough for NiMH
batteries.

Fast-charging is a different issue, because the methods used to detect
"full charge, stop cramming!" on NiCd and NiMH batteries are somewhat
different. A fast-charge circuit originally designed for NiCd
batteries only, may end up damaging NiMH batteries.

Many of the aftermarket-batterypack companies which advertising in QST
etc. will either sell you a NiCd-based replacement pack, or a
NiNH-based pack with the option of buying a NiMH-aware fast charger.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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