On Mon, 30 May 2011 11:26:06 -0700, (Dave Platt)
wrote:

This was also for a brand new cell, as repeated
charge/discharge cycles would also decrease the cell capacity.

Had these cells been "formed" properly prior to your test (via several
slow-charge / slow-discharge cycles)?

Nope. They came directly out of the box. I didn't record how long
they had been sitting on the shelf. I must admit my ritual was rather
sloppy.

I would initially charge the battery in a Radio Shock 23-1305 charger.
http://www.buzzillions.com/reviews/radio-shack-30-minute-battery-charger-4-aa-aaa-batteries-reviews
Not the best, but I have 3 of them, so they get used. One big
advantage for me is that it will independently charge a single AA
cell. Also, it runs off 12VDC. It came with 4ea NiMH cells, but I
killed them long ago.

After charging, I would leave the battery sit for anywhere between 1
and 8 hrs to let it cool down and supply sufficient time to charge up
more cells. I vaguely recall that they were Sanyo cells, but as I
have several types on the bench, I can't tell which one was used.

I would then connect the battery to the CBA-II tester, plug in the
desired test settings, and generate a graph. Repeat for several
cells. I would usually try to discharge it until the "knee" is
visible, which my guess(tm) is down to about 15% of capacity.

I haven't done much NiMH testing (mostly because Li-Ion is my current
interest), but I do recall seeing a drop in capacity with every cycle.
There was no evidence of any "conditioning" effects. Incidentally,
until I see numerical or personal evidence of such a "conditioning"
requirement for NiMH batteries, I prefer to ignore it. To me, it's
the same as NiCd "memory effect", which I have yet to experience, and
which I have spent considerable time attempting to demonstrate.
http://en.wikipedia.org/wiki/Memory_effect

There seems to be a general
agreement that NiMH cells don't achieve their maximum storage capacity
unless they've gone through several cycles like this,

I'll believe it when I see it demonstrated, documented, or chemically
explained. I just wasted some time searching Google Scholar for any
references to NiMH conditioning, training, pre-charging, etc. Zilch.

and that many
manufacturers don't take the time to do this during the manufacturing
process. I've seen some indication of this in my own testing (using a
smart-charger which can cycle the batteries and report the capacities
for each cycle).

I was watching some TV show (How it's made???) showing how batteries
are manufactured. "Testing" the batteries was done on a high speed
conveyor and lasted about 1/2 second per cell. I don't think this is
enough time to "condition" the battery.

As far as I have been able to guess (Yeah, I know, I should have
measured), the typical NiMH cell arrives out of the box at about 30%
charge. I don't know if this is intentional, an artifact of the
manufacturing process, or some safety requirement. There are quite a
few battery vendors proclaiming that they ship NiMH and other
batteries discharged for safety reasons. Anyway, if they ship them
discharged, then the "conditioning" cycle would need to be:
Full - discharge - Full again - test - discharge
I wouldn't expect such an exercise for consumer products.






--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558