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Old Mar 26, 2011, 10:08 AM
dirtyballs is offline
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Bart
he runs a 24x10 prop on 16S that sounds way better then 32x10

24x10 and 250A

your setup will have 0.4V more per cell under max load, half load it will be 0.6 volt per cell. I think you are going to blow your ESC.

Everybody that tries to decrease power of a setup by restricting the throttle, will one way or the other have a problem. You should setup the system that can withstand the full power, if it is not capable of doing that, you should change prop, or ESC and motor.

maybe you should start a threat in the "giant electric plane" forum https://www.rcgroups.com/giant-electric-planes-477/

That's the place to be with this kind of setup.

DB
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Old Mar 26, 2011, 11:58 AM
KiloOne is offline
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Dale Kramer
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Both of us are saying restricting 'power' not 'current'. Restricting power will achieve what I want. The current during an 'on' pulse is another matter. Over 9000 rpm and 10" pitch does not achieve my goals. I will be flying around 30 mph. I know I should have a lower kv but I am still willing to risk the test at this point. The WYE termination should help a little to bring the rpm down. I will let you know the results.

Perhaps it would have been better to start this in 'Giant electric planes' but I have already sent this thread link out to a lot of people to follow the project and I don't want to have 2 threads going.

Thanks for your input.
Dale
Old Mar 26, 2011, 12:16 PM
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Page five is perhaps worth a read.

https://www.rcgroups.com/forums/show...1&d=1300706894

If my personal safety was at stake I would not exceed 50% of the ESC rating. One minor fact about ESCs which is most often overlooked is that as the voltage goes up the max. amps. rating for them goes down.

Charles
Old Mar 26, 2011, 12:49 PM
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Dale Kramer
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Good reading Charles!

I was thinking of replacing the 2460 uf's of 63v caps on the Spin 300 with a bunch of 300 uf 75v caps I have and now I am pretty sure I will. Maybe I can stop that chain reaction. Again, I would not have tried to push the Spin 300 this way except that I know it has been done successfully. I got 100 of the 300 uf 75v caps for adding every 6 inches to my power leads from my packs to the Spin 300.

Dale
Old Mar 26, 2011, 08:43 PM
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Nice to see this thread from the creator of the Lazair. My uncles have been asking me about big hobby motors for the last few years and it always comes down to battery's being so much more expensive than a pair of Rotax 185's and a fee gallons of gas.

With your charging setup what are you doing to generate the DC needed?
Old Mar 26, 2011, 09:35 PM
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Nice thing about light twins is that one engine will carry you all the way to the scene of the crash. Just kidding

This project reminds me of when I first got into electrics some 20+ years ago. Yeah, wet power was cheaper and easier, but the challange was what brought the real fun and excitement to the electrics.

Good luck with your project, and please do keep us informed of how it goes.

Norm
Old Mar 27, 2011, 12:11 AM
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UAV Integrations
Have you considered advanced cooling methods for the ESCs? Either liquid cooling or possibly a peltier effect cooler? These add weight and consume precious battery power, but they could be the necessary safety net for your electronics.
Old Mar 27, 2011, 02:55 PM
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Dale Kramer
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Helno

I will have my chase vehicle bring along an 8 kw gas generator that I use between flights to charge the batteries. The AC from this will be converted to the DC inputs the PL8's need by the Dell sever power supplies. I will be able to charge up after a flight in about 1/2 the duration that the flight was.

Norm

Actually when I look at the purchase price of the 96 5000 mah 4s batteries that I bought and will fly with ($32.89 each delivered), as pre-paid gasoline, I only need to get about 170 charge cycles out of them before I equal the cost of what gas and oil would have cost for the same flight time.

I already have some batteries cycling at about 200 cycles at the rate I will be discharging them and five times what I expect to discharge them at. They have only lost about 10% of their original capacity. I am very happy so far with these very lightweight cells.

I am convinced that right now it will be cheaper to replace old 185 Rotaxs with an electric setup like this.

plilthyy

Yes I have (Schulze boat 300 amp) but again, the value decision for the Spin 300 won out at this point.


I now have all the batteries I need, I am attaching a spreadsheet of their weights and voltages as received. The average DeltaV for all 104 batteries was only 7mv and the max DeltaV was 90mv followed by 36,36,35,27mv and the rest were under 20mv DeltaV. Standard deviation was 10mv. Much better than anticipated.

Dale
Last edited by KiloOne; Mar 27, 2011 at 10:02 PM.
Old Mar 27, 2011, 04:11 PM
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Is this the electric lazair you were referring to as one already flying?


http://inhabitat.com/transportation-...-takes-flight/
Old Mar 27, 2011, 04:22 PM
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Dale Kramer
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Yes it is.
Old Mar 27, 2011, 05:22 PM
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I have not looked at the site lately but the last time I tried to dig around that site I could not find any real info on the specs of their plane. Would be nice to know more about it.
Old Mar 27, 2011, 06:58 PM
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Your post makes for an interesting statistical question. A lot of people love to rag on hobbyking batteries.

You just bought over 100 of the exact same battery, how many were DOA?
Old Mar 27, 2011, 07:26 PM
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Dale Kramer
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People can rag all they want. Look at my post and spreadsheet above more closely.

There were no DOA batteries. I have a friend that flies Zippies and has had great luck with them. Maybe HK got their problems sorted out. To my knowledge you can not even come close to the value for your money from anything else.

Dale
Old Mar 27, 2011, 07:49 PM
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Nice to see that you had such good results. I've never owned any different brand but have yet to have and DOA stuff.

This might interest you a bit. I have been working on a simple digital instrument cluster aimed at ultralight's and inspired by the Lazair. My uncle owns a Lazair I am sure you know him through Upac. The airspeed indicator he has is basically useless at the low end of the Lazairs flight regime. I figure that better indication could be possible using the same types of instruments that are used on small UAV's and if you are going to do airpseed you might as well add on an altimeter a compass and a few engine instruments all in one simple display.
Old Mar 27, 2011, 07:59 PM
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Dale Kramer
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I am sure you will do well with your instrument.

Personally I fly with no flight instruments.

I will have an engine display for each engine (watts, mah used, volts and engine temp). I will have my Iphone in my shirt pocket with apps for navigation, weather, internet posting of my position and to make phone calls if I need to.
Last edited by KiloOne; Mar 28, 2011 at 11:35 AM.


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