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<DIV dir=ltr align=left><SPAN class=279073519-18092008><FONT face=Arial
size=2>You had a decision many of us will have sooner or later.. to use a
known 'going bad' battery for trim flights - and what we may not realize is
that we have to fly almost full stick to get any type of performance from the
pack - thus loading it heavily. A 5 minute, or less, flight at almost full
stick, can be very dangerous - as you found out. The trick to any battery
longevity - meaning years, is to pull out as little current as possible (as
slowly as possible) from the pack during each flight (a more efficient motor
will help this also). You can imagine one extreme, taking say, 1 amp out slowly,
the batteries would last for 10 years (a guess). That said, there is
another battery function that also helps, and that is to get a greater
capacity battery so even though you pull 3000mah (3A) from the battery on a
flight, if the battery were rated at 20Ah (our batteries are rates around 5Ah),
taking 3A from this battery would only be taking a fraction of the total
capacity, and not be an issue. However, weight will be an issue with current
battery technology. I think the ladder is where we are headed, with the
increased Burst rating of the newer cells = lower IR. Having a burst of 160A
(new 5200's) is much better than a burst of 109A (5300's), and if we could find
a burst rating of 200A, that would be better yet. </FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=279073519-18092008><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=279073519-18092008><FONT face=Arial
size=2>sc</FONT></SPAN></DIV><BR>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
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<FONT face=Tahoma size=2><B>From:</B> nsrca-dist7-bounces@lists.nsrca.org
[mailto:nsrca-dist7-bounces@lists.nsrca.org] <B>On Behalf Of </B>krishlan
fitzsimmons<BR><B>Sent:</B> Thursday, September 18, 2008 10:52 AM<BR><B>To:</B>
CA, AZ, HI, NV, UT<BR><B>Subject:</B> Re: [NSRCA-dist7] LiPo cell
configuration<BR></FONT><BR></DIV>
<DIV></DIV>
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<TD vAlign=top>This is exactly what happened to my pack that caught on
fire last Friday Scott. I had a good feeling a cell or two was bad as my
performance was down on this pack pretty good, but I figured I'd use it as
a 5 minute trimming practice pack.. I assume it got really hot in flight
as I had the stick pegged most of the 3 or 4 minutes that it was in the
air. It was super hot and one cell was split open when I took the belly
pan off. I won't use my other packs now that are down on "noticeable power
anymore. Too much at risk to keep flying them for me. Had I had a Cellpro
charger, I might have never flown that pack that day. <BR><BR><BR><BR>
<DIV><STRONG><EM><FONT face="comic sans ms" color=#0000bf size=3>Chris
</FONT></EM></STRONG></DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV><BR><BR>--- On <B>Thu, 9/18/08, Scott
<I><scottcov@comcast.net></I></B> wrote:<BR>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: rgb(16,16,255) 2px solid">From:
Scott <scottcov@comcast.net><BR>Subject: Re: [NSRCA-dist7] LiPo
cell configuration<BR>To: "'CA, AZ, HI, NV, UT'"
<nsrca-dist7@lists.nsrca.org><BR>Date: Thursday, September 18,
2008, 1:49 AM<BR><BR>
<DIV id=yiv33896232>
<DIV dir=ltr align=left><SPAN class=965342908-18092008>Don, I have 4
5300's that are the one's I have been using for a long time (years).
Mine too, pull my plane well, but comparing them to new packs, the drop
off in performance over time has been so subtle I notice little
difference until I compare them to new packs. The difference is very
evident. However, my larger concern is fire.. as I place more demand on
cell BANKS that may be bad (or going bad), the heat builds up much
more.. and the potential for fire, in my mind, increases. This happens
when charging and discharging (flying). Imagine a cell or TWO being
puffed inside a 4s BANK of cells inside the black heat shrink. There is
a chance you would not see this unless you are looking close.. which I
have done, and have replaced these packs. The stress on the remaining
good cells within the 4s bank is extreme. Things have been pretty quiet
lately regarding fires with LiPo, but we must not forget the potential
is still there and using old packs (any packs for that matter), where
the IR has increased, is concerning to me. I have 2 packs (5300) that
run hot and I don't think I'd fly them in 90 degree plus outside temps
as they would really come down hot after a flight. The new packs
(5200's) are not even warm to the touch. Oh, just FYI, I have replaced
my 5000 V2 Extreme pack with the new 5200 cells. I am not recommending
the 5200's yet, they are too new yet, but it seems they have good
potential. Also, here is San Jose, the outside temp's are rarely
over 90.. but up in Sac or AZ, this happens much more often. If I lived
in these areas I'd be a bit more concerned. </SPAN></DIV>
<DIV dir=ltr align=left><SPAN
class=965342908-18092008></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN
class=965342908-18092008>sc</SPAN></DIV><BR>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
<FONT face=Tahoma><B>From:</B> nsrca-dist7-bounces@lists.nsrca.org
[mailto:nsrca-dist7-bounces@lists.nsrca.org] <B>On Behalf Of
</B>AtwoodDon@aol.com<BR><B>Sent:</B> Wednesday, September 17, 2008 9:31
PM<BR><B>To:</B> nsrca-dist7@lists.nsrca.org<BR><B>Subject:</B> Re:
[NSRCA-dist7] LiPo cell configuration<BR></FONT><BR></DIV>
<DIV></DIV><FONT id=role_document face=Arial>
<DIV>Scott, like you, my TP5300s (4P) configuration have lasted into my
3rd season flying electric. Yep, they are tired but will still
pull my plane vertical as far as I need, just not quite as much
gusto. All my other batteries are 1P configurations but I have not
seen that show significantly better or worse balancing challenges.
I agree, the 1P configuration would make it easier to detect a single
cell developing higher IR.</DIV>
<DIV> </DIV>
<DIV>I have one FP5350 (2 5S packs) as well as 2 TrueRC 5000 mah packs
(each 2 5S packs). The FPs have been solid with about 75 flights,
no issues, pretty easy to balance while charging. The 2 TrueRC
packs need a little more balancing during charge but everything finishes
out fine. They have less than 30 flights each.</DIV>
<DIV> </DIV>
<DIV>I did check one of the TrueRC packs on Jim's Cellpro and all 10
cells were in the 3.5 milli ohm range, one cell was slightly higher at
about 4 if I remember correctly. The new Cellpro 10s is
interesting and there is a very good review and subsequent discussion
about it on RC Groups.</DIV>
<DIV> </DIV>
<DIV>Don</DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV>
<DIV>In a message dated 9/17/2008 9:05:48 P.M. Pacific Daylight Time,
scottcov@comcast.net writes:</DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"><FONT
style="BACKGROUND-COLOR: transparent" face=Arial>
<DIV><SPAN class=279212203-18092008><FONT face=Arial>Hey Electric
Guys,</FONT></SPAN></DIV>
<DIV><SPAN class=279212203-18092008><FONT
face=Arial></FONT></SPAN> </DIV>
<DIV><SPAN class=279212203-18092008><FONT face=Arial>I'd be interested
in what LiPo battery configuration you are using.. 5S2P, 5S4P, 5S1P...
other. Why?.. read on. I believe the less "P" you have in the battery
the easier to balance and possibly the longer life you will get due to
better cell balancing before charging. I have recently converted to a
new cell by TP, some of you saw this at the Hollister contest. The
5S2P, 5200 pack, is working great. Jim Oddino and I checked the
internal cell resistance, which was around 3milli-ohms (if I recall
correctly). This battery puts out 156A burst, the older 5s4p, 5300
pack put out 109A burst. My thinking is this, the lower "P" pack you
have the easier to keep the battery in balance. If you have a 4p pack,
any one of the 4p cells can degrade over time, causing the 4p 'bank'
to not supply as much sustained current - causing the whole battery to
be weaker. Jim and I played with a Cellpro 10S charger, and I think we
concluded that it would be difficult for any charger to
determine if any one cell in a 4p bank was going bad (you
can only monitor the bank IR, not the individual cell within the
bank). However, if you had a 1p 10S pack, you could easily tell if the
cell was gaining resistance as it aged. On a 2p pack, the resistance
CHANGE may not show up as easily as a 1p pack but much easier than a
4p pack. We are trying to determine here when a 5S pack is getting
weak (yes, we can see as we fly - but if we could determine as it
happens, perhaps we can correct this by charging differently). Jim O
mentions he has not seen a battery with as low of internal resistance
readings as the new TP pack, which equates to more power, less heat in
use, and I hope longer life. I will mention here that my 5300,
5s4p packs have lasted 2-3 years and many, many flights, but
they are getting old.. and the new packs may last 3-4 years..
they are also around $250 each.. a reduction in price from the 5s4p
packs. I believe even newer technology will soon show us a 10s1p
pack from TP - and some may have this now from other
manufacturers.</FONT></SPAN></DIV>
<DIV><SPAN class=279212203-18092008><FONT
face=Arial></FONT></SPAN> </DIV>
<DIV><SPAN class=279212203-18092008><FONT face=Arial>I'd be interested
in your opinions on this topic.</FONT></SPAN></DIV>
<DIV><SPAN class=279212203-18092008><FONT
face=Arial></FONT></SPAN> </DIV>
<DIV><SPAN class=279212203-18092008><FONT
face=Arial>Scott</FONT></SPAN></DIV>
<DIV><SPAN class=279212203-18092008><FONT
face=Arial></FONT></SPAN> </DIV><BR><BR>_______________________________________________<BR>NSRCA-dist7
mailing
list<BR>NSRCA-dist7@lists.nsrca.org<BR>http://lists.nsrca.org/mailman/listinfo/nsrca-dist7<BR></FONT></BLOCKQUOTE></DIV></FONT><BR><BR><BR>
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