[NSRCA-dist7] LiPo cell configuration

[Scott]

Chris, between YOU AND ME.. hang on for a few weeks. I'm getting a Cellpro
10S and will test this based on what I wrote. I think I can get you a 'deal'
on one if it works out. If you are using a 1S configuration, that charger
using the IR readings should tell you how the batteries are holding up.. but
the bottom line is, if the batteries are going bad - changing IR often, the
cells are going bad - nothing you can do about it other then know they are
going bad, but you will know this based on how the plane is flying also. So
hang on a few weeks and let me test this charger a bit.
 
sc

  _____  

From: nsrca-dist7-bounces at lists.nsrca.org
[mailto:nsrca-dist7-bounces at lists.nsrca.org] On Behalf Of krishlan
fitzsimmons
Sent: Wednesday, September 17, 2008 10:22 PM
To: CA, AZ, HI, NV, UT
Subject: Re: [NSRCA-dist7] LiPo cell configuration


I remember this conversation from the contest. Glad you brought this up. I'm
curious to know how my bad packs test out. I may have to get a cell pro.
Mine are 1p's and I like them that way. Less cells can go bad in my way of
thinking. 
As I sit here contemplating the fact that I need to buy new batteries, this
is very interesting to me. It's also interesting that the TrueRc packs that
I have been considering, possibly aren't getting as good of reviews after
people have several flights on them.  Not sure why. I'm sure the cell
chemistry is similar to others. I'm pretty baffled at what packs to buy. I'm
still leaning towards the TrueRc as I figure if they get me 100 cycles a
set, then I pay like 2.50 per flight. Similar to glow. And I probably fly
about 100-150"pattern" flights a year (yes, I know, I need more practice)
lol. So spending 250-350 per year on batteries is fine with me. 
I sure do know that my $2300 that I bought last year are shot at this point
because of my charger that I was using. 
Taking my 2 good set's to the field in the morning to fly, well, 2 flights.
lol.. 

Interesting topic here. 



Chris 
 
 
 


--- On Wed, 9/17/08, Scott <scottcov at comcast.net> wrote:


From: Scott <scottcov at comcast.net>
Subject: [NSRCA-dist7] LiPo cell configuration
To: dist7 at nsrca.org
Date: Wednesday, September 17, 2008, 9:04 PM


Hey Electric Guys,
 
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.
 
I'd be interested in your opinions on this topic.
 
Scott
 
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