[NSRCA-discussion] My next electric

[Richard Strickland]

I had a very long discussion with Kokam early on about cycles.  All of their numbers were all taken from VERY low charging and discharging rates--all well below 1C levels--more like .1-.5C.  At that time I think they were talking about 1400 possible cycles(degradation to 80%) and I developed a theory based on that number and 1C.  It went something like this: Capacity 5000, discharge rate--say average around 8C (40 amps)/ flight. So 1400 divided by 8 = 175 cycles.  But wait, there's more--so you are bumping up the charge rate over 1C to 2C and charging affects battery life just like discharging--so take your 1400 divided by 2 = 700 divided by 8 and that equals 87.5.
 
So the trick is (in this model) to try to get your average usage/draw down and don't charge over 1C.  
 
But there's even more....The numbers assume an 80% capacity usage so let's drop the example to 50 % and a 6C draw (30 amps average). 5000 ma packs. 1400 divided by 6 = 233 X 1C charging rate= 233--but then you are only using 62.5% of the 80% design figure--so 233 divided by 62.5 would yield 372.8 cycles.
 
So it looks like throttle end point management, the right motor,
airframe, and prop along with some experimenting with controller settings can yield some good cycle numbers.  You can use smaller batteries--but don't expect super cycle life out of them.  This jibes pretty well with my somewhat limited experience lately.
 
The batteries have gotten better lately--so these numbers are bound to improve.  I've been off the list for some time and if all of this has been hashed over and is old news--I apologize.
 
RS




From: lightfoot at sc.rr.comTo: nsrca-discussion at lists.nsrca.orgDate: Tue, 5 Aug 2008 16:32:11 -0400Subject: Re: [NSRCA-discussion] My next electric




How many of you guys get 1000 cycles out of your Lipos?
 

Jay Marshall 
-----Original Message-----From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of brian youngSent: Tuesday, August 05, 2008 1:49 PMTo: General pattern discussionSubject: [NSRCA-discussion] My next electric
 

just kidding....
 
http://www.airventure.org/2008/8sun3/electra_flyer.html
 
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