On Mon, 30 May 2011 12:02:45 -0700, "William Sommerwerck"
wrote:
"Dave Platt" wrote in message
...
There seems to be a real tradeoff. In general, the very-high-
capacity NiMH cells seem to have a more rapid rate of self-discharge;
they're good for "use immediately after charge" applications, but not
so good for "charge and store" standby uses.
That hasn't been my experience. My 2200mAh and 2700mAh MAHAs hold up very
well -- months, in fact. I've never made a study of the actual capacity, but
they /do not/ "fall flat" shortly after being put into use.
The reason I bought a CBA-II battery tester was because of my
inability to properly guess actual battery capacity.
Most of my experience with NiMH batteries was with Metricom radios and
various Motorola and Kenwood handheld radios. It doesn't take much to
kill them. For example, you don't even need to discharge them to a
NiMH battery pack. The country distributed Motorola MTS2000 radios to
all the hospitals as part of the HEARNET (Hospital Emergency
Administrative Radio Network) system. The radios were permanently
planted in charger with power on 24x7. Some radios were turned on,
but most were left off. There would be a short test roughly twice per
month. After about a years, not one of the radios were functional
because all the NiMH batteries were dead.
I'm having a similar experience in my palatial office, where I use a
Motorola HT600 and several NTN7016A NiMH battery packs. Unlike the
hospital example, I make it a point of not leaving the battery in the
charger after it reaches full charge. I also use the radio in a
normal manner, charging the battery only when the xmitter craps out.
The result is that I charge the battery approximately 3 times per
week. Despite this care, I manage to kill about one battery every 2
years (that's after only about 150 charge cycles).
I also use NiMH batteries in my various cameras (Canon S5IS etc) all
of which use AA cells. I'm seeing the typical 1%/day self-discharge
rate. I keep two sets of batteries in the bag. It's not unusual for
me to find the spares to be nearly dead after about 2 months.
Your NiMH milage may vary, but mine sucks.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558