Dave Platt wrote:

NiMH has some advantages and some disadvantages over NiCD. Biggest
and most obvious advantage is greater capacity. Biggest disadvantage
is a somewhat higher self-discharge rate - NiMH batteries can lose
20-30% of their charge per month just sitting on the shelf un-used,
while NiCd batteries can hold their charge quite a bit longer.

Motorola claimed that their NiMH cellular batteries for the old "flip phones"
lost as much as 1/3 of their charge in the first week. My casual experiments
showed me they were pretty close.

Contrary to many maker's claims NiMH cells do develop "memory". When
flip phones were popular people used to give me their old batteries that
would no longer hold a charge. 99% of them were NiMH and most of them came
back to normal after being "reconditioned".

They were reconditioned by a charger that did three discharge/charge cycles
in a row. It was a "smart" charger, it could determine if a battery was NiCad
or NiMH and charge accordingly.



For this reason, NiMH is probably not the best choice for
batteries/packs which will spend weeks or months sitting in your ARES
"go-pack" - they'll probably have self-discharged just when you need
'em.

I've been happy with the couple of purchases that I made from
Batteries America (http://www.batteriesamerica.com/). We bought a
bunch of the 6-AA-cell battery holders for the Icom W32, and the
fit/finish/function of the cases seems as good as Icom's own product
at a rather lower cost.

I've never dealt with them, but my recemendation is for AA packs.
You can charge them more easily in stand alone chargers, mine will do six
at a time. You can also keep a set of NiCads or alkeline batteries for
an emergency spare.

If you do keep a set of alkeline batteries make sure to buy a good brand,
and rotate them.


They can also sell you cells, or complete insert sets, if you want to
try cracking open your existing battery pack and rebuilding it.

Being far away from ordering the batteries from companies catering to
the ham replacment market, I've done it often with battery packs sold
for cordless phones. They come in many sizes and capacities. Make sure
to remove and re-install any diodes, heat sensors, fuses, etc in the
old pack.


As a general rule, you _can_ use a charger designed for NiCd batteries
with NiMH batteries, but may not get the best results (in terms of
total capacity and/or number of charge/discharge cycles).

I agree with that. It's also important to make sure that your charger
really does work propely. Over the years, I've bought several used
packs that were "cooked" by bad chargers, or overcharging. I've even
had an Icom one that cooked batteries on its own. :-(

Geoff.


--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM
IL Voice: (07)-7424-1667 IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838
The trouble with being a futurist is that when people get around to believing
you, it's too late. We lost. Google 2,000,000:Hams 0.