On Fri, 5 Jul 2013 08:21:45 -0400, "Wild_Bill"
wrote:
I've spent more time than I'd like to admit, looking for the high capacity
4/3-A NIMH cells, and the too-long 67mm length was all I could find.
Well, there's nothing wrong (in my opinion) using the too short A
battery size cells.
Yep, battery specs are a bit mystic (intentionally it seems) as there can be
a rated capacity and then a slightly higher average or nominal capacity.
The specs seem to have been written by battery manufacturers looking
for very high numbers to make their products look better. I normally
use high discharge rate cells at ummm.... high discharge rates. Yet
many of the capacity tests are done at C/20 or less, resulting in
highly inflated numbers. All I can suggest is try to find the data
sheet and determine how a cell was tested before accepting the number
printed on the garish shrink-wrap coverings.
The cells in the pack I opened previously were marked with a somewhat
standard number on the metal shell, NT410LAH.. no brand or other info on the
skins which is typical for commercial/industrial cells, but you knew that.
That number is similar to a GC industrial cell number.
This dead NIMH pack may have had the terminals shorted at one time, it's
used so anything's possible.
I recall seeing a couple of components in images of rechargeable cells
(Duracell, maybe) that are built-in to prevent destruction by shorting
and/or charging at an excessive rate, (although they may not provide
protection on a cells which were aleady partially discharged from normal
use).
You may be thinking of the common LiIon 18650 cell, which has a disk
shaped PCB on the negative terminal end to protect the cell.
https://www.google.com/search?tbm=isch&q=18650+protection+circuit
Diversion: I just love the names given to the various 18650 batteries
such as Trustfire, Truefire, Ultrafire, Fireworm, Marsfire, etc.
Somehow, such names fail to inspire confidence in the safety of their
products.
I'm thinking those components are a thermistor and a poly-fuse (possibly a
3rd component), and had suspected that these military cells are shorter
because those items were left out, since they absolutely wouldn't be used in
consumer applications, thus liability protection not being needed.. just
speculation.
I've never seen any per-cell protection on a NiCd or NiMH battery or
pack. There are some PCB's found in radio battery packs that are
coulomb counters, but I don't think there are any that offer short
circuit protection for the individual 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