<!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 6.00.2800.1458" name=GENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY id=role_body style="FONT-SIZE: 10pt; COLOR: #8000ff; FONT-FAMILY: Arial"
bottomMargin=7 bgColor=#ffffff leftMargin=7 topMargin=7 rightMargin=7>
<DIV><FONT color=#000000>I had an NMP failure today. Tuesday night I charged the
battery with the NMP charger and tested it. Under no load it was showing 8.44
volts. </FONT></DIV>
<DIV><FONT color=#000000></FONT> </DIV>
<DIV><FONT color=#000000>Since I'm paranoid I run two batteries, two
regulators and two independent switches each going into the RX. My primary
pack is on a 5.7 voltage regulator and the other is on a 5.1 voltage regulator.
This causes all power to be drawn from the primary pack unless it drops below
5.1 volts. Today I went flying and everything went well, however, upon returning
home I put the primary battery on the NMP charger and the charge needle didn't
move. After determining the pack was bad I tore it apart and found one cell at
</FONT><FONT color=#000000>3.87 volts and the other at 0.23
volts.</FONT></DIV>
<DIV><FONT color=#000000></FONT> </DIV>
<DIV><FONT color=#000000>Based on the amount of voltage drop on the backup pack
I believe the primary pack powered one or two of my flights today. Unfortunately
I was lazy and didn't check the voltage between every flight so I don't know
when it died. Luckily though I did have a backup battery so I didn't loose
my plane "IF" the pack did die during flight.</FONT></DIV>
<DIV><FONT color=#000000></FONT> </DIV>
<DIV><FONT color=#000000>These packs were purchased March 2004 but weren't used
until around May this year, they have 69 flights on them. Keep in mind that the
only one of the two that has been repeatedly drawn down is the one that
failed.</FONT></DIV>
<DIV><FONT color=#000000></FONT> </DIV>
<DIV><FONT color=#000000>Other info, I store my plane in my garage which does
get quite hot here in TX, but certainly not up to 140 deg. I don't store
my plane in my care other than during transporting to and from the field. Today
was a rather mild day in the lower 90's to upper 80's when I was
flying.</FONT></DIV>
<DIV><FONT color=#000000></FONT> </DIV>
<DIV><FONT color=#000000>I post this for others' info and to see if anyone has
any info on why this would have failed, I'm not posting to badmouth NMP.
In fact, </FONT><FONT color=#000000>I've really liked the way the NMP
batteries have performed up to this point. They are light, easy to charge, and
provide a lot of flight time. However this failure is quite
disconcerting.</FONT></DIV>
<DIV><FONT color=#000000></FONT> </DIV>
<DIV><FONT color=#000000>Keith Black</FONT></DIV>
<DIV><FONT color=#000000></FONT> </DIV>
<DIV><FONT color=#000000></FONT> </DIV>
<DIV><FONT color=#8000ff>----- Original Message ----- </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="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=pattern4u@comcast.net href="mailto:pattern4u@comcast.net">Grow
Pattern</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto:discussion@nsrca.org">discussion@nsrca.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, August 04, 2005 10:53
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Li-ion chargiing failures</DIV>
<DIV><BR></DIV>
<DIV><FONT color=#000000>I have had a few (4) of my 2000 mAh Li-ions fail in
the last couple of months.</FONT></DIV>
<DIV><FONT color=#000000></FONT> </DIV>
<DIV><FONT color=#000000>The failure only occurs during charging and when the
outside temperature is very hot. </FONT></DIV>
<DIV><FONT color=#000000></FONT> </DIV>
<DIV><FONT color=#000000>I was not sure what it was at first. I did read the
warnings on some cell phone batteries that I use as set-up packs, and it says
do not get hotter than 140F. Yesterday I actually caused it to happen at the
field (and when I was taking notice.)</FONT></DIV>
<DIV><FONT color=#000000></FONT> </DIV>
<DIV><FONT color=#000000>I had a spare 2000 pack in my van, left over from my
Nat's trip. It was on the tailgate area and caught some sun. It was showing
8.12 V so I plugged it in to charge it up. The meter did not move, so I
tested the voltage again. No volts. My laser-temp showed 143 F. After a
teardown I found one cell as good as open with .05V. </FONT></DIV>
<DIV><FONT color=#000000></FONT> </DIV>
<DIV><FONT color=#000000>Based on other feedback I believe that what happens
is the cell blows a sort-of-fuse internally if hot (140+ F) and a charge is
applied. Could be a safety feature for all that know?</FONT></DIV>
<DIV><FONT color=#000000></FONT> </DIV>
<DIV><FONT color=#000000>It does not (or has not so far) failed if current is
drained when this hot. I have one in a Radio South ni-starter that get warm
and is mistreated , but does not fail.</FONT></DIV>
<DIV><FONT color=#000000></FONT> </DIV>
<DIV><FONT color=#000000>In practical terms what happens to you is that when
you switch on there is no juice. So no juice, no fly, no plane
loss....</FONT></DIV>
<DIV><FONT color=#000000></FONT> </DIV>
<DIV><FONT color=#000000>Please regard this as a "heads-up' to not charge your
Li-ions if they are hot. Wait until they cool down.</FONT></DIV>
<DIV><FONT color=#000000></FONT> </DIV>
<DIV><FONT color=#000000>Regards,</FONT></DIV>
<DIV><FONT color=#000000><BR>Eric.</FONT></DIV>
<DIV><FONT color=#000000></FONT> </DIV>
<DIV><FONT color=#000000></FONT> </DIV></BLOCKQUOTE></BODY></HTML>