Discussion List (Batteries)

[Gray E Fowler]

Richard

In the world of batteries, modelers aint nuthin'-especially pattern dudes. 
In the military, battery applications are critical, but any application 
like we use them, that is 60 amps for 8 minutes is a short term disposable 
application best handled by a chemical-thermal battery. Military drives 
such battery technology and it probably is what the pattern flyers are 
gloming off of, but the batteries croak simply cuz they are pushed too 
hard. If the military or anyone else IS driving the technology, do you not 
think that the battery suppliers would pass on such info as your cool 
down/heat discharge process to keep pattern dudes from frying their 
expensive batteries?

My point is that this technology will not be ready for the average pattern 
flyer for quite some time(5 years)  if ever.

Good luck, it is good to hear honesty about these batteries. Most people 
flying them dodge life cycle questions -"all so new-dont know yet" which 
reminds me of a Rodney Dangerfield joke.......

I grew up in a tough neighborhood.......a guy came up to me and my friends 
once and asked us "how long does it take to get to the subway from here" 
our response was...."dont know....no one's ever made it yet".-tough 
neighborhood.



Gray Fowler
Principal Chemical Engineer
Composites Engineering



"Richard Strickland" <richard.s at allied-callaway.com> 
Sent by: discussion-request at nsrca.org
11/18/2005 11:58 AM
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Gray, Dean,
 
While my experience wasn't the greatest--it really wasn't all that bad 
once we had the bugs worked out.  BTW, it was a Hacker system like 
Jason's.
One of the issues was to determine how cool the batteries needed to be 
before putting them back on charge; another was to make sure you were not 
over or under charging.  Another was to make sure they were balanced.  But 
for me it came down to weight and longevity.  Contrary to where your 
information is coming from, my understanding is that modeling IS driving 
this battery segment along with the military.  I'm reasonably confident 
there will be significant breakthroughs like that nano-tech unit(Toshiba 
or some other heavy-hitter like that) posted earlier this year that will 
impact the market fairly shortly.  The 3200s were under-sized, but 4000s 
would be also.  The motors would peak out at 67-69 amps on application of 
full throttle and back down to the 63-65 range.  This system worked well, 
but we were too close to the edge to lose any capacity and complete an FAI 
flight.  Temps started with a 40-50 degree rise when we started using them 
in the upper 70s and 80s and the same and a little more as ambient got 
warmer.  They got too hot.  We also tend to fly out.
 
Realistically, if to get decent mileage out of these things and have to 
stay close to 10C; then you've got to have at least 6000s+ and keep the 
weight down.  I know zip about batteries, except how to design conveyor 
systems for them, but they almost need to act like a capacitor--very high 
charge, discharge rates, and unlimited cycles with no damage.  I can't 
imagine there aren't MANY folks working on that concept.
 
Of course there are other alternatives--lighter and/or smaller airframes, 
different motor, ESC, prop combinations--but if you want unlimited 
vertical with 11 lbs--then your're going to draw 55-70 amps.
 
Richard
----- Original Message ----- 
From: Gray E Fowler 
To: discussion at nsrca.org 
Sent: Friday, November 18, 2005 10:57 AM
Subject: Re: Discussion List (Batteries)


Richard 

I am not a battery expert, but like everyone else on the list that does 
not stop me from having an opinion about batteries. 
First, electric airplanes do not exactly drive the battery 
market,......even if 50% of the FAI finalists use them. No other 
applications 
that I am aware of uses these batteries in the manner that we attempt, 
which is that massive current draw. What electric planes do 
to batteries is damaging, as demonstrated by your 25 flights.   
I would not expect the battery market to develop a battery capable of long 
life and extreme current draw since no one else uses 
batteries in such a manner. 

Invest in bottle of Windex, clean the oil. 



In fairness to the manufacturers, I don't think they really understood 
that
guys potentially would go out and fly 50+ flights per week.  When I 
finally
got all my infrastructure charging act together and made time to
practice--which wasn't all that much, I still was clicking along at a 35
flight/week pace right up to our first contest in mid June.   As you may
recall, I was using 20C 3200s on a shared cost beta program.  At 11 lbs.,
the airplanes were gobbling up 63-68 amps at times and significantly 
heated
the batteries and shortened their lives.  The manufacturer came out with
some 15C 4000s--but there was still the problem of amp draw and heat.  The
consensus at that point is the batteries aren't very happy at much over 
10C.
The problem I had/have is anything over the smaller batteries was going to
blow the weight limit--plus, as more information was coming out from some 
of
the top guys that they were getting around 50-60 flights on the larger
packs.  Since I'm not a top dog, I would pretty much have to foot the 
entire
bill to switch to the larger units.  As it appeared to me--the batteries
just aren't quite up to the task for the average guy--so I made an interim
decision to go back to IC for the rest of the season--hoping the battery
guys would come up with something more acceptable for '06.

That didn't pan out very well either, so I was effectively out for the
season.  (Lots of other contributing factors also)  What I told the 
battery
manufacturer was what a guy really needs is five sets of batteries(with 
the
then current stuff) and immediate service for turnaround.  Have three sets
for flying and one or two sets traveling to/from.

I'm sold on electric--particularly for a guy with limited practice time. I
could go on and on....

Richard 



Gray Fowler
Principal Chemical Engineer
Composites Engineering
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