[NSRCA-dist7] LiPo cell configuration

[AtwoodDon at aol.com]

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.
 
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.
 
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.
 
Don
 
 
 
 
In a message dated 9/17/2008 9:05:48 P.M. Pacific Daylight Time,  
scottcov at comcast.net writes:

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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