<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=Content-Type content="text/html; charset=iso-8859-1">
<META content="MSHTML 6.00.2800.1400" name=GENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY bgColor=#ffffff>
<DIV><FONT face=Arial size=2>Frank</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Your points are well taken. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>If I interpret your statement regarding NiMH packs
"looses capacity on stand" correctly as self discharging when idle, I haven't
found this to be the case. I suspect that all NiMH cells aren't created equal
(as with most things) and that the technology may have improved. Specifically,
I've found that the Sanyo 1650mah NiMH AA cells retain their charge better than
most NiCads I've used. One "test" pack has demonstrated 80%+ capacity after
being on the bench for 6 months. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I agree with your statements regarding NiMH being
less tolerant of abusive charging. I've looked at the behavior of a few
different "quick" chargers on the bench with instrumentation. A couple of them,
even though they offered a NiMH selector, severely overheated packs.
I concluded that the Sirius Pro Charger does a nice job without excess
heating.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Living in Houston pretty much allows me to dismiss
any low temp deficiencies.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Overall, I find NiMH performance to be superior to
NiCad for pattern use. Performance defined as reliability, weight vs. capacity,
and cost / value. I do prefer to use a 5-cell pack with a regulator to avoid the
possibility of low voltage dips during high current demand (NiCads are better
here - but I would still use 5 cells). </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Earl</FONT></DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=frankbis@adelphia.net href="mailto:frankbis@adelphia.net">Frank
Bis</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto:discussion@nsrca.org">NSRCA Discussion List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, May 08, 2004 11:01
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Safety Concerns Charging
Lithium-Ion and Solid Anode lithium Batteries (Duralite)</DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial size=2>I have been working in the battery area for 40 +
years so let me pass on my knowledge. When the Duralites first hit the
market I went on line and said "<STRONG>Be very careful with these solid
lithium anode cells</STRONG>"- they can vent catch on fire etc especially
after repeated cycling. The reason for this is after several charges the
lithium forms Dendrites (spikes on the surface) which punch through the
separator and short out the cell. No one paid any attention to
this. Now in the case of the Lithium-Ion these cells <STRONG>DO NOT LIKE
TO BE OVERCHARGED.i.e. above 4.2 volts.</STRONG> They will vent and
catch on fire. I use them in flat packs but each cell has a protective
circuit on the cell and can be charged at constant current using a standard
charger at 250 mA. When any cell in the two cell pack reaches 4.2 V
the protective circuit on the cell senses this and takes the cell off line,
hence the battery of two cells off charge. Yes these battery packs are a
bit lighter and have a higher energy density (Wh/kg). Let me pose this,
Nickel-cadmium cells are a proven technology and can be fast charged safely
and work. Why not stay with they. The Nickel-metal hydride is a
good system. However, it looses capacity on stand, and requires careful
field charging to prevent it from getting too hot and venting. Also it
does not work as well at low temperatures. My advice stay with
Ni-Cd.</FONT></DIV></BLOCKQUOTE></BODY></HTML>