[NSRCA-dist7] LiPo cell configuration

[krishlan fitzsimmons]

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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