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<DIV><FONT face=Arial>Chad</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Sure - nothing wrong with going with what provides the
highest comfort level. Given the same technology - and often the same
manufacturer - the differences between brands can come down to service provided.
As you say - they all have their limits. We on the gulf coast are envious of
your ambient temps for battery life (you can keep it for human life.)
:) I've noted much better life from batts used during our "winter" than the
heat of our summer.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>At least we get a bit of a break with the shorter F3A
sequences (the Masters guys need all the capacity they can get).
</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Earl</FONT></DIV>
<BLOCKQUOTE
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=chadnortheast@shaw.ca href="mailto:chadnortheast@shaw.ca">Chad
Northeast</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">nsrca-discussion@lists.nsrca.org</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, March 14, 2008 10:44
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion]
Batteries</DIV>
<DIV><BR></DIV><FONT face="'PrimaSans BT,Verdana,sans-serif'">Its just my
general "feel" from my experience with TP, and witnessing others experience
with FP. I won't go into all the details on the list because I don't
want to tarnish any particular company, but I have yet to see any of the 1P
packs come close to the longevity of the 4P packs when putting them through
the same punishment.<BR><BR>I have seen a lot of puffed 5350's, 5300's, 5000's
so I guess they all have their limits :)<BR><BR>Chad<BR><BR></FONT><FONT
face="'PrimaSans BT,Verdana,sans-serif'"><BR>----- Original Message
-----<BR>From: Earl Haury <ejhaury@comcast.net><BR>Date: Friday, March
14, 2008 9:10 am<BR>Subject: Re: [NSRCA-discussion] Batteries<BR>To:
chad@f3acanada.org, NSRCA Mailing List
<nsrca-discussion@lists.nsrca.org><BR><BR>> Chad, you have a point,
however it's important to factor in that <BR>> the 1P <BR>> packs are
also generally higher C rating. My view when <BR>> considering batteries
<BR>> initially was that higher cell count provided more failure <BR>>
opportunities, <BR>> both as individual cell failure and connections.
I've <BR>> disassembled a number <BR>> of "failed", or no
longer pattern suitable packs, and <BR>> measured individual <BR>> cell
characteristics.<BR>> <BR>> Generally, the cells in a lower C pack tend
demonstrate an <BR>> increase in <BR>> impedance, resulting in lower
voltage output for a given current <BR>> draw over <BR>> their lifespan
until no longer "pattern viable". During this <BR>> time capacity <BR>>
diminishes - but most cells with high impedance will still <BR>> retain
80+% of <BR>> their original capacity. Even though these things generate
more <BR>> heat than <BR>> the higher C packs - they tend to handle
abuse (as you've found) <BR>> partly <BR>> because of the retained
capacity and partly because of <BR>> "performance <BR>> limiting"
impedance. Post flight imbalance doesn't change too <BR>> much as these
<BR>> packs age - suggesting a similar "aging" of the individual
cells.<BR>> <BR>> Conversely, the high C packs demonstrate very low
impedance <BR>> initially and <BR>> that appears to be retained
throughout their life. However, the <BR>> cell <BR>> capacity appears to
drop pretty early and continue to do so over <BR>> the pack <BR>> life.
I've measured some of these with an average capacity loss <BR>> of 40%
after <BR>> 50 flights - that means a 5000 mAh pack is now a 3000 mAh pack.
<BR>> Even worse - <BR>> there is often a good deal of variance from
cell to cell. Their <BR>> low <BR>> impedance will provide little
warning (as loss of power) until a <BR>> cell is <BR>> injured, real
easy to do if you try to take 3500 mAh from the <BR>> now 3000 pack.
<BR>> Often one will notice the post flight imbalance increasing as
<BR>> these packs <BR>> age and it will be greater at higher depths of
discharge - a <BR>> sure sign some <BR>> cells are getting weak. OTOH -
for blazing power the high C <BR>> packs are the <BR>> way to go - but
there's a price to pay in life, weight, & $$.<BR>> <BR>> These
observations have led me to surmise that a pack with a <BR>> high enough C
<BR>> rating to minimize impedance losses (and accompanying heat) and
<BR>> a low enough <BR>> C rating to allow good capacity retention
should provide the <BR>> best value for <BR>> pattern. I have no idea
just what construction parameters / <BR>> chemistry <BR>> defines these
characteristics. I chose to try the FlightPower <BR>> F3A packs <BR>>
because they are mid-C rating and 5350 mAh capacity. So far they <BR>>
provide <BR>> good power and generate no more heat than the high C packs
I've <BR>> used. I <BR>> expect that the extra capacity (above 5000)
offers a little <BR>> buffer if there <BR>> is a capacity decline over
their life. I see little balancer <BR>> activity with <BR>> these packs
regardless of depth of discharge (say 3000 mAh vs <BR>> 4000 +) so <BR>>
far, time will tell - we're all still learning.<BR>> <BR>> Earl<BR>>
<BR>> Team FlightPower<BR>> </FONT><BR>
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