Discussion List (Batteries)

Fri Nov 18 10:16:07 AKST 2005

Hi Rich,
Yeah, at 70A, you are going to use every little bit of 4.0 AHr. That's based on my flying P07.
You need a bare minimum of 5 AH so you aren't drawing the battery down too far.
I tested the FMA discharge protection module, for a while. It's a neat item, though too heavy for much of us, and the connectors are not rated for our currents.
It shuts the throttle down if any one cell hits 3.0V.
With some disassembnly and connecvtor replacement, it would be a great safety item!
The Skyvolt balancing charger is a dandy item, though. I will be using it hereafter. I intentionally unbalanced a pack, and put it on: voila, charged and balanced with no extra effort.
I have to make up an adapter to allow me to hook a TP style balancer connector and Deans Ultra combo  to its special output connector.
I also want to put together a rig so I can look at each cell voltage, conveniently, at the end of a flight.
It doesn't need to be done every flight, but often enough to see if a cell keeps coming up weak. 
That would be replacement time.
more to come,

Dean Pappas 
Sr. Design Engineer 
Kodeos Communications 
111 Corporate Blvd. 
South Plainfield, N.J. 07080 
(908) 222-7817 phone 
(908) 222-2392 fax 
d.pappas at kodeos.com 

-----Original Message-----
From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]On Behalf Of Richard Strickland
Sent: Friday, November 18, 2005 12:58 PM
To: discussion at nsrca.org
Subject: Re: Discussion List (Batteries)

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  <mailto:gfowler at raytheon.com> 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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