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<DIV><FONT face=Arial>Tim</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Thanks for the info - kinda hard to find my old favorite
(Channel Master Color TV Tuner Cleaner).</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Earl</FONT></DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=timsautopro@yahoo.com href="mailto:timsautopro@yahoo.com">Tim
Taylor</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">General pattern discussion</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Sunday, December 05, 2010 9:38
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion] "Sick"
Lipo Packs</DIV>
<DIV><BR></DIV>
<TABLE border=0 cellSpacing=0 cellPadding=0>
<TBODY>
<TR>
<TD vAlign=top>
<DIV>Stablint 22, available at radio shack, Best connector cleaner
enhancher I know of.</DIV>
<DIV> </DIV>
<DIV>We use it quite a lot at work on Auto electronic circuit
problems.</DIV>
<DIV> </DIV>
<DIV>Tim<BR><BR>--- On <B>Sun, 12/5/10, ehaury <I><<A
href="mailto:ejhaury@comcast.net">ejhaury@comcast.net</A>></I></B>
wrote:<BR></DIV>
<BLOCKQUOTE
style="BORDER-LEFT: rgb(16,16,255) 2px solid; PADDING-LEFT: 5px; MARGIN-LEFT: 5px"><BR>From:
ehaury <<A
href="mailto:ejhaury@comcast.net">ejhaury@comcast.net</A>><BR>Subject:
Re: [NSRCA-discussion] "Sick" Lipo Packs<BR>To: "General pattern
discussion" <<A
href="mailto:nsrca-discussion@lists.nsrca.org">nsrca-discussion@lists.nsrca.org</A>><BR>Date:
Sunday, December 5, 2010, 10:29 AM<BR><BR>
<DIV id=yiv55551994>
<STYLE></STYLE>
<DIV><FONT face=Arial>Chris</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Thanks for the info - pretty much answer's the
puffing question.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Let me add my thoughts / observations as to why
things can not be all good with charging / balancing related to
pattern packs and the common chargers we use.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV>
<DIV><FONT face=Arial>So what about "charge abuse"? My observations
suggest that balancing equipment doesn't always do what is
expected. Many balancers function by drawing charge current away
from the high cell(s) which allows the low cells to "catch up".
Part of the problem lies with the balancers capacity to divert
that charge current - usually 300 - 500mAh - which isn't
sufficient when charging at 5A. If the
charger primarily terminates on total pack voltage, the high
cell(s) are pushed too high until the average reaches the target
pack voltage. This will often leave the weak cell low and some
too high and won't be noted unless the individual cell voltages
are observed. (The way to charge packs packs with large imbalance
is at a rate that doesn't exceed the diversion capacity of the
balancer - takes time.) On a good note, most systems will
terminate charge (with notification) if the high cells are pushed too
far - still not good for them (especially without consideration
for temperature) but an important safety feature that should prevent
charging eruptions as well as providing notification that something
isn't right. </FONT><FONT face=Arial>Then there are chargers that
balance by either charging each cell independently or by adding
current to the low cells to help them "catch up". This is a good
strategy and that appears ideal except for issues with connectors
/ leads.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>A common problem is that both balance methods
can be compromised by the balance leads / connectors themselves which
can result in the balancer actually misbalancing the pack. The
connectors are small and of materials that will oxidize over time.
They also tend to lose tension with use. Both the looseness and
oxidation results in a poor connection. A marginal connection
will prevent the balancer from "seeing" the correct voltage and will
become worse as balance current flows. (Ever have a "balance lead not
connected" or "incorrect cell count" report - these are indications
that the connectors are not doing their job. This all is 10X true if
charging at 5A is attempted through these faulty connections!
Additionally, the balance leads themselves are small gauge wire of low
strand count (not very flexible) which often results in several
strands breaking from the connector with use. Eventually the wire
might break off - in the meantime it's a resistor in the balancing
circuit! I've also seen extensions (have all the same problems) where
only a couple of strands were captured in crimping to the connector!
The good news is that much of this can be avoided with maintenance and
observation. Contact cleaners will help keep the connections clean,
the some female connectors can be removed from the housing (one at a
time if on the batt) and "bent" back closed when they loosen. Check
connections on new leads / extensions and always fix the problem if
some lead "wiggling" is needed to make the charger happy.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Earl</FONT></DIV></DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV>---- Original Message ----- </DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial; BACKGROUND: #e4e4e4"><B>From:</B> <A
title=f3aflyer7@gmail.com
href="http://us.mc623.mail.yahoo.com/mc/compose?to=f3aflyer7@gmail.com"
rel=nofollow target=_blank
ymailto="mailto:f3aflyer7@gmail.com">Scott Pavlock</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="http://us.mc623.mail.yahoo.com/mc/compose?to=nsrca-discussion@lists.nsrca.org"
rel=nofollow target=_blank
ymailto="mailto:nsrca-discussion@lists.nsrca.org">General pattern
discussion</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Sunday, December 05, 2010
7:59 AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion]
"Sick" Lipo Packs</DIV>
<DIV><BR></DIV>Chris ,<BR><BR>Great article!<BR>Were can we find the
rest of it.<BR><BR>
<DIV class=yiv55551994gmail_quote>On Sat, Dec 4, 2010 at 8:36 PM,
Chris <SPAN dir=ltr><<A
href="http://us.mc623.mail.yahoo.com/mc/compose?to=cjm767driver@hotmail.com"
rel=nofollow target=_blank
ymailto="mailto:cjm767driver@hotmail.com">cjm767driver@hotmail.com</A>></SPAN>
wrote:<BR>
<BLOCKQUOTE
style="BORDER-LEFT: rgb(204,204,204) 1px solid; MARGIN: 0pt 0pt 0pt 0.8ex; PADDING-LEFT: 1ex"
class=yiv55551994gmail_quote>
<DIV>Stu is right, all cells in the pack were subjected to the
same overcharge or over discharge and will also fail as the first
cell did. One event will probably not show up as a swelled
cell but it is the overcharge / over discharge over many cycles
that will result in swelling. Notice the article says that max
voltage is temp related, and most chargers don't make this
adjustment so even with a "good" balance charger, you can still
overcharge.<BR><BR>Chris<BR><BR>Part of a good article:<BR>
<DIV><I>This was the common problem with many cheap Chinese LiPos
of around 2005-2008. Most are better now, but it's the #1 cause of
premature LiPo failure: water contamination in the plant. Many of
China's LiPo factories are on the coast, where the altitude is
very low and the humidity is high. You can't run the humidity too
low on the assembly floor, because you're working with volatile
chemicals that could explode in the presence of a spark, and you
can't run it too high because then you end up with a worthless
LiPo that swells on first use.</I></DIV>
<DIV><I>Here's the science. You have three ingredients that are
functional in a LiPo battery. The rest is wrapping and wiring
attachments.</I></DIV>
<UL>
<LI><I>Cathode: LiCoO2 or LiMn2O4</I>
<LI><I>Separator: Conducting polymer electrolyte</I>
<LI><I>Anode: Li or carbon-Li intercalation compound</I>
</LI></UL>
<DIV><I>I'm going to be a little vague in my language here. The
chemicals involved vary according to manufacturers, so I don't
want to make any assumptions.</I></DIV>
<DIV><I>Remember your chemistry class? Note the absolute <B>lack
of any hydrogen atoms in the reaction</B>. None, zero, zip, nada.
If you have <B>water inside your battery</B> -- and virtually all
batteries have a little bit -- you've got problems. When the
chemical bond of H20 is broken by electrolysis and heat, you end
up with free oxygen. You also have free-roaming hydrogen that
typically ends up bound to your anode or cathode, whichever side
of the reaction it's on and depending on the state of charge of
your battery.</I></DIV>
<DIV><I>Now, this is a pretty unstable situation that's
exacerbated by any over-discharge or over-charge condition
creating metallic lithium in your cell. The end result is Lithium
Hydroxide: 1 atom of lithium, one atom of hydrogen, and one atom
of oxygen.</I></DIV>
<DIV><I>But you still have a free oxygen atom floating around
inside the battery casing, that typically combines with one other
oxygen atom -- O2, or what we sometimes think of as "air" -- or
two other oxygen atoms, to form a characteristic tangy,
metallic-smelling substance called "ozone", or O3. Gases expand
with heat and contract with cold. Chuck a swollen battery in the
freezer and it might come out rock-hard again... until it heats
up. It's not frozen, it just got cold enough that the gases inside
didn't take up much space at all.</I></DIV>
<DIV><I>And that free O2 or ozone is just waiting to pounce and
oxidize some lithium on the slightest miscalculation on your part.
The modest over-discharge during a punch-out, or running the
battery a little too low or letting it get a little too hot, or
running the voltage up to 4.235v/cell on a cold day when the
actual voltage limit per cell is more like 4.1v. All of these
create the perfect storm for a puffy battery to quickly turn
itself into a ruined battery or an in-flight fire.</I></DIV>
<DIV><I>Understanding the role of free oxygen in your battery,
from water and other causes, is CRUCIAL to understanding why
batteries fail, and why sometimes you can get by with flying a
puffy battery, and sometimes you can't.</I><BR></DIV><I>If a
Lithium battery is overcharged or charged too quickly, you end up
with LOTS of excess free lithium on the anode (metallic lithium
plating), and free oxygen on the cathode. A free oxygen atom is
small enough to freely traverse the separator without carrying an
electric charge, resulting in lithium OXIDE on the anode. Lithium
"rust", in reality. Useless to us at this point, just dead weight
being carted around inside your battery's wrapper.</I>
<DIV><I>But lithium oxide uses fewer oxygen atoms than existed in
the ionized state, so you end up with, again, FREE OXYGEN. And
people wonder why if you over-charge a LiPo underwater, it still
ignites despite the lack of open air...</I></DIV>
<DIV><I>If it's over-discharged or discharged too quickly, the
reverse is true, but you end up with Lithium Oxide on the cathode,
but at a lower rate because there's simply less there. Basically,
an abused battery quickly develops corrosion on both poles of the
battery inside the wrapper. And the more it's abused, the worse it
gets as the resistance goes up and it still gets driven
hard.</I></DIV>
<DIV><I>This, by the way, is the most common cause of swelling
today for our aircraft when flown with a high-quality pack (not
knock-off eBay leftovers from expensive Chinese mistakes of
2004-2009). The reality is, these kinds of cells, regardless of
their 'C' rating, are built for use where they last for several
hours... not several minutes. While the chemistry if used as
designed is good for thousands of cycles, we're driving them so
far out of spec that we're lucky to get hundreds of cycles out of
them.</I></DIV>
<DIV style="FLOAT: right"><I></I></DIV>
<DIV><I>In most cases, too, our batteries are under-specced. If
slow-charged and slow-discharged, many of these packs would often
hold considerably more mAh than we think they do. That's one of
the reasons we get the performance we do from them. Higher-C-rated
packs also often introduce gelled electrolyte into the separator,
and carbon or phosphorous nano-structures on the anode and cathode
mixtures rather than the "pound it out thin and hope it's mixed
right" approach used with sheets of anodes & cathodes
today.</I></DIV>
<DIV>
<DIV></DIV>
<DIV class=yiv55551994h5><BR><BR>On 12/4/2010 8:23 PM, Stuart
Chale wrote:
<BLOCKQUOTE type="cite">Been there done that but my experience
is that before long additional cells will fail and the cycle
will continue. With the cost of the lower priced
packs, ie: Zippy's I would no longer bother :) <BR><BR>On
12/4/2010 6:45 PM, Ron Van Putte wrote: <BR>
<BLOCKQUOTE type="cite">Those of you who use lithium polymer
battery packs to power their competition airplanes are
familiar with "puffed" packs. I recently had four
elderly 5S packs "puff". We all know that's not good,
but what I'd like to know is what's actually happening.
<BR><BR>I know it's probably not wise for consumers to take
lithium polymer packs apart, but that's exactly what I did
with four packs. I discovered that in three of the
"puffed" packs, only a single cell was "puffed". In the
last pack, there were two "puffed cells. I did a little
arithmetic and quickly discovered that I could make three
"unpuffed" packs from the good cells I had. So, I
unsoldered the "puffed" cells from the four packs and
cannibalized one pack to make three 5S packs from what I had
left. This process is obviously for the timid or the
careless. I was careful and had no mishaps.
However, I would suggest that anyone who says "Oops" a lot
should not attempt doing this. <BR><BR>The three 5S packs I
have left are "rock solid". Experienced electric-pilots
will know just what I mean. <BR><BR>I have flown these packs
and they seem to perform just as they did in their "youth".
<BR><BR>My questions are: Why do lithium polymer cells
"puff"? What is the likely future of my recovered 5S
packs? <BR><BR>Ron VP
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