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Old Oct 16, 2014, 07:29 AM
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You think there will be a day when we see 20-30 min flight

Times with batt's and under 10 min full charge? I'm talking wide open full throttle flight for 20 min?
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Old Oct 16, 2014, 07:53 AM
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Staffs, UK
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Not sure what you mean by "Times with batt's" ? Or "under 10 min full charge" ? And like anything else it depends what you're expecting of your flights.

But 20-30 minute flights with electric models are easily possible now. Just choose the right model. But it won't be very fast or very aerobatic if that's what you're looking for.

Steve
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Old Oct 16, 2014, 07:58 AM
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20-30 min flight times with batteries. Yes, I'm talking wide open full throttle loops, rolls, invert, pulling hard G's.

You think science will develop and bring to market a decent sized battery that will allow for 20 min flight times with full throttle and then a full charge in less than 10 minutes.

I saw a few months back think it was in Middle East was a battery using graphene(sp) complete full charge in under a minute.
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Old Oct 16, 2014, 08:15 AM
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Flying for 20 minutes at full throttle is possible with current battery technology. All you have to do is prop the motor so it pulls current at 3C or less. Sorry about the recharge time.

Larry
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Old Oct 16, 2014, 08:50 AM
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Yes.
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Old Oct 16, 2014, 09:37 AM
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Its already here, my little $25.00 used Hobbyzone mini cub can fly full throttle for about 40 minuets

For bigger suff with a optimized power system and airframe its easily doable.

Recharge: not yet.
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Old Oct 16, 2014, 09:45 AM
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Joined May 2013
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A powered glider with a 2m wingspan can fly with a wide variety of motors.... and if you put a rather small one on it and power it with a 3000mAh battery it could fly wide open for half an hour.... I suspect the motor could only produce approximately 10oz of static thrust and it would require some skill to stay aloft.

The real question I suspect you're asking is do we think we will ever fly a reasonably fast plane wide open for half an hour.... and my answer is "possibly", but we're all waiting for the next true breakthrough in batteries.

The humorous thing to contemplate is how many folks will incinerate speed controllers when that day arrives... I suspect current battery tech is saving at least some hardware right now because of duration issues.
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Old Oct 16, 2014, 10:28 AM
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Some gliders can do well over half an hour un-powered.

So purely for a power model, - assuming a biggish model requiring a 1000w continuous for half an hour, it becomes a watts/half hour thing.

For a 1000w, if up the voltage you need less amps, (watts = volts x amps), and the amps x time side tend to control the batteries capacity.

An 8s or 10s pack should be able to fly full throttle at 1000w for quite a long time.

(Someone else can do the maths to determining what capacity the pack would be )
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Old Oct 16, 2014, 11:17 AM
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only with solar panels.
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Old Oct 16, 2014, 01:12 PM
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Someone need to check my 'guess work', but -

1000w at 10s, (say 110v or 10 x 11v)
Amps = watts / volts
1000 / 110 = 9.1Amps (say 9A it's easier)
9A = 9000mA

So for 1 hour at 1000watts you need 9000mAh capability.
Say 25% reserve capacity =12000mAh capacity for 1 hour.
or 6000mAh battery capacity for half an hour flight at 1000w continuous with 25% reserve.

Turnigy do a 6000mAh Lip.

Right or wrong ?

WOOPS!. Very wrong , the 10s should be nearer 37v to 40v . I used 11v (a 3s) and multiplied by 10. 110v did seem just a touch high
I should go back to sleep.
Thank you Steve.
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Old Oct 16, 2014, 01:39 PM
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I have flown powered gliders and been in the air for an hour. It actually gets pretty boring looking up that long although it’s fun to search for and find the thermals.

I also have a plane that will suck a battery dry in 5 minutes at full throttle. It actually gets pretty intense after that long going so fast. Do you really think you want to fly WOT for 20 min?

I’m happy with what I get with the current battery technology though. And graphene? I wouldn’t hold my breath too long for that.
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Old Oct 16, 2014, 01:57 PM
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No, I'm not looking to full wide open throttle for 20 min, but if it can be flown full throttle for 20 min you could fly at 1/2 throttle for 40 min and that's what I want.

Instead of changing Batt's every 7-9 mins. I'm not talking gliders... I'm talking t-28's with fly times of 30 mins.
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Old Oct 16, 2014, 02:11 PM
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have you asked here? http://www.rcgroups.com/forums/showthread.php?t=867259 if these guys are not the experts on experimenting with flight times on the T-28, then no one is.
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Old Oct 16, 2014, 02:36 PM
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Who can say? It all comes down to battery technology really. Motors and ESCs don't have much room for improvement. Airframes are limited by the laws of physics and fairly well understood. All else being equal the way to get longer flight times is to pack more energy into the same size/weight battery. I suspect we'll see incremental improvements for a while but at some point it will plateau and then we'll need a completely new battery tech. Fuel cell perhaps? Who knows.
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Old Oct 16, 2014, 03:27 PM
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Staffs, UK
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Quote:
Originally Posted by eflightray View Post
Someone need to check my 'guess work', but -

1000w at 10s, (say 110v or 10 x 11v)
Amps = watts / volts
1000 / 110 = 9.1Amps (say 9A it's easier)
9A = 9000mA

So for 1 hour at 1000watts you need 9000mAh capability.
Say 25% reserve capacity =12000mAh capacity for 1 hour.
or 6000mAh battery capacity for half an hour flight at 1000w continuous with 25% reserve.

Turnigy do a 6000mAh Lip.

Right or wrong ?
One teeny problem. 110V is 30S not 10S....that's a BIG battery (and 110V is deadly if you get a shock from it).

Go back down to 10S and you could have about 350W for 6000mAh but for 1000W you need more like 30A and so 18,000mAh. That's several big batteries. But not completely impossible I guess.

Steve
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