On Tue, 31 May 2011 14:37:43 +1000, "Phil Allison"
wrote:
** You got something against NiMh cells ?
Yep. I don't like them.
I would never mistreat NiMH AA cells the way you just have.
I didn't have time to do it the right way (20 hr discharge). I can do
it again with a longer discharge time and lower current. I still have
several of both brand of cells that I haven't mistreated yet. However,
it will take about a week to produce results (plus dragging home a
spare computah to do the test and building a better battery holder).
15 minute charging is absurd for any cell NOT designed for such abuse - it
causes overheating with new cells and destruction of older ones.
True for the Duracell, which recommends 205ma for 15 hrs to recharge
printed on the cell. The Energizer Recharge battery doesn't specify a
charge current:
http://data.energizer.com/PDFs/nh15-2000.pdf
However, the recommended battery charger is a quick charger:
http://data.energizer.com/PDFs/ch15mn2.pdf
with a 15 minute charge time.
I've been testing batteries since about 2005 while working on a
product that I won't discuss. However, I will point out that many
NiCd batteries can be quick charged at ridiculously high rates, as
long as certain (unspecified) conditions are met. If you don't mind,
I'll leave this unsubstantiated.
Incidentally, the Sanyo ENELOOP battery data sheet recommends fast
charging at 2A for 1.1 hrs:
http://www.eneloop.info/fileadmin/EDITORS/ENELOOP/DATA_SHEETS/HR-3UTGA_data_sheet.pdf
A 1C discharge test will never give the rated capacity figure with NiCd or
NiMH.
I indicated that in my posting as:
I didn't want to wait 20 hrs per test to get the official rated
capacity, so I elected to run the tests at 1C which resulted in about
a 45 minute test, but also resulted in a much lower capacity result.
The purpose of the test was to see if a brand new battery required
several charge-discharge cycles before it would deliver full capacity,
not to measure the actual rated capacity in a 20 hr discharge test.
IME - the idea that new cells have a "running in "period is a MYTH
invented by retailers back in the 1970s when consumers were first sold AA
and C size NiCds and found their performance disappointing when compared to
alkalines.
Maybe. There was also quite a bit of effort in the mid 1990's by
manufactures to differentiate their NiMH products from NiCd. For
example, I found a pair of Lenmar NoMEM Pro NiMH batteries, which are
an obvious shot at the alleged NiCd "memory effect". Another
possibility is that some support droid needed a line to get rid of a
complaining customer and invented the "conditioning" for the purpose.
The inherent lower terminal voltage and cell mAH capacity were the real
reasons.
Agreed. I went through the mess with alleged "9V" (6 cell) NiCd
batteries, being more like 7.2VDC. With a nominal operating voltage
for 1.2 to 1.3 VDC for NiCd and NiMH, anything designed for a 1.5VDC
alkaline is going to have a problem.
Incidentally, all of the marine radios I helped design were required
to function down to 10.0VDC applied power. They couldn't reach rated
TX power at 70% of rated voltage, but still had to belch at least a
few watts of RF and remain functional.
I'm rather mystified by the results. Although the improvement in
capacity after 3 charge-discharge cycles is minor (10-15%), it still
seems for real. My previous tests didn't show such an increase in
capacity. Instead, it showed a deterioration in capacity. However, I
was testing for something quite different, and was working with a mix
of old and new cells.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558