On Sun, 29 May 2011 14:59:03 +0000 (UTC), "Geoffrey S. Mendelson"
wrote:
Jeff Liebermann wrote:
This was also for a brand new cell, as repeated
charge/discharge cycles would also decrease the cell capacity.
Funny, I've always read the opposite with Nimh cells, they need to go through
several charge/discharge cycles before they reach full capacity.
I've never seen that. Nothing similar found with Google or on my
favorite sites:
http://en.wikipedia.org/wiki/Nickel-metal_hydride_battery
http://batteryuniversity.com
http://batteryuniversity.com/learn/article/Nickel_based_batteries
Where I have seen something like this is with cheap Chinese laptop
battery packs. The problem is not the battery. It's the charge
controller inside the battery. It has to be run up and down in
voltage and "trained" before it knows how the pack is going to act.
This is usually done at the factory by reputable battery pack
manufacturers, but seems to be avoided by others. I've personally
only seen this with Li-Ion battery packs, but am told that it's also a
problem with older chemistries.
This is especially true of the long discharge ones, which come "pre-charged"
at about 80% and then at least in my experience take 5-10 cycles to come
up to a useable capacity. It also seems in my experience that the lower the
charge rate, the more cycles a cell needs.
That's probably because NiMH has a rather high self-discharge rate.
They may have been at 100% when they left the factory, but have
self-discharged in the box. Also, the ideal storage charge level is
about 40% for NiMH. None of the NiMH batteries I've tested (Duracell,
Rayovac, Sanyo, Energizer, various no-name, and various OEM) have
showed anything other than a slow loss of capacity (area under the
curve) for repeated charge/discharge cycles.
BTW, if you have any info on charging an Azden HT, please let me know.
No experience. This might help if it uses NiMH:
http://batteryuniversity.com/learn/article/charging_nickel_metal_hydride
Note that most of my experiments have been on single cells, not
battery packs.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558