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<DIV>I could guess that the next Master schedule is going to be electric friendly. </DIV>
<DIV class=signature id=signature>--<BR>Vicente "Vince" Bortone</DIV>
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<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #1010ff 2px solid">-------------- Original message -------------- <BR>From: "Earl Haury" <ejhaury@comcast.net> <BR>
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<DIV><FONT face=Arial>Chad</FONT></DIV>
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<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>
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<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>
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<DIV><FONT face=Arial>Earl</FONT></DIV>
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<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>> conside
ring 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>> ag
e 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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