1 hour 20 minutes
- APM 2.5 takes the world record for Multi-Copter Duration of Flight powered by a rechargeable battery. [note:  records also exist for hover that can occur indoors and take advantage of ground affect]

Flight Requirements:

- Distance > 1 kilometer

- Minimum elevation from ground the greater of 2 meters or two prop diameters (no ground affect)

- Lands within 50 meters of Launch

- Minimum of two way points > 0.25 km apart

- Altitude Climbs: Two climbs > 100 meters each

- Ends before voltage drops below recommended minimum level for recharging

- Flight over ground that does not vary more than + 20 meters in elevation

Actual Flight

- Distance: 1 - 2 km

- Min elevation 2 meters

- Ended at start

- Three way points with two 0.3 km apart

- Two climbs:  126 meters and 112 meters

- 13.06 volts left with 10 volt recommended minimum

- Ground + 10 meters

Time:  > 1hr and 20 minutes (81.43 minutes)

Multi-copter:

- Octa 2XQuad 6Up+2Dn (wanted to fly something novel that would show off the flexibility of APM 2.5)

- 3.18 kg AUW

- Li-Ion battery

Attached are the flight logs.  Later I'll provide:

o Video

o Earthview of flight

o Altitude gains

o Details of the copter (design and weights)

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Sorry about the slow reply.  Trekking and internet access is limited.

The prop used on the ship above almost performed as well as this odd prop listed as a 16" but actually is a 15.6".

16x55 DJI S800 Carbon Imitation at HobbyKing part #39781

I haven't fully tested it, but it does show promise.  Also, there is no guarantee that what you will get is what I got.  But Hobby King so far has been quite reliable.

Documented flight is as you know different than hover.  Flight infers significant:

- distance and

- changes in elevation.  

Please don't get me wrong.  Hover is a great test method and equally important in developing the technology. Most all of my preliminary tests were hover tests within and above ground affect.

The following have a huge impact on increasing flight duration, and as such are not used in this record flight:

- ground affect or thermals

- non-rechargeable batteries

Use of both easily takes flight over two hours.  But, some of us want to get there in 2014 under the constraints described in the requirements.  We might actually make it.  My brother and his grandson might try this "winter" in Arizona with a quad.

Also, it is easy to meet even flight parameters if you perform the feat over uneven ground.  Thermal effects can keep a multi-copter in the air for quite a while.

If there is documentation on the two hour flight (battery type, hover vs. flight, over flat ground of used thermals, etc.) please let me know.  All I want to do is learn and share.

On vibration, I was surprised by the low amount of vibration.  When I get back from trekking, I'll show the flight data on that.  When flying a light frame dampened by heavy mass (the battery or 3/4 the battery plus a camera), the battery mass makes a wonderful dampener.

Pulso U39M 300KV 67gr. motor

Hello Emin,

are you sure the Shorai 18A   can supply 15 volts continuously ?

It seems to me that battery is designed to supply 12 volts .

Shorai Batteries require a charging system output of 13.1 Volts or higher at idle, and must not exceed 15.2 volts at maximum output.

The most interesting data of this battery, even if the voltage is  "only" 12 volts is the discharge rate 27C in specs or around 15C if we consider 270A for a 18 A battery.

In tests:

- rotors most efficient (net lift per gram thrust) at 3S

- but rotors at 3S are not always able to meet minimum 2x power range over hover

- and wiring carries lower amps so can sometimes be a lower gauge and less weight

- penalty range of 4S is typically 1% to 3% (but may be neutral or better if include wire weight improvement)

- going higher than 4S means using heavier ESCs that add an additional penalty

I have yet to find an exception.  But I'm only testing a limited range of rotors and I've never gotten a fundamental explanation as to why higher voltage would be less efficient in light of the fundamental fact that higher voltage means lower amps in the wiring which mean less heat loss.  If you have insights into this, please explain.

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I'm also interested in why lower voltage is more efficient. I'm seeing the real world tests, and I can't understand why higher isn't better for long fly. The reason that power transmission lines run at thousands of volts is because there's power loss as a percentage of power sent than if they just pumped wall voltage down the line. Plus the wires can be thinner, the switching equipment smaller.

If you need to drive your motor at 100 watts to hover, you could drive it with 20 amps at 5 volts or 5 amps at 20 volts. As long at the ecs is rated for the volts and amps, I can't understand how lower voltage with higher amperage is more efficient, it feels counter-intuitive.
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I have conducted some research on the cell number and all of that stuff. Some cool equipment has been utilized, including a 10" oscilloscope, LCR meter and simulation software. Conclusions: 1) it seems to be true that lower C is more efficient. 2) reasons are quite different from what was claimed by fellow hobbyists on this thread. Motor coil inductance isn't big enough (around 46uH) to thoroughly smooth out the pwm pulses, so the current ramps up high and down almost to zero, which increases the active power dissipation, the load on caps and battery and also may bring the magnetic material closer to saturation point, which decreases the magnetic efficiency. And greater the voltage - greater the current ramping amplitude (though the dependency is linear, not quadratic as EOD noticed). It could be well cured by rising the pwm frequency by about 10 times, which would make the current through the coil in active phase almost constant, thus decreasing ramping and eliminating active losses on high voltage. However this may (or may not) be hard to do due to insufficient microcontroller processing power and the fixed adc sampling rate, which has to get voltage samples between every pwm pulse.
Next move for me is to plot the power (I*U) dependency vs input voltage on the constant RPMs af running motor. This will show the real scale of these effects.
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Old Yesterday, 02:59 PM
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... please be precise, with voltage current is (approximately) linear, power is quadratic (nothing else I stated above). Also you simply forget the losses in the windings ( = copper wire of a certain diameter and a certain length), which have a certain resistance.


best regards
Ferdinand
xAlot
The secret behind the "lower voltage - better efficiency" is that ESCs emulate part load by bursts of full throttle. So the less your throttle stick, the shorter the bursts. This means the minimum voltage your copter can fly, has the longest full throttle bursts.

If you now have a given motor/prop that runs with X Watt having a given Voltage of Y Volt at full power (generating a current of Z Amps). At every throttle stick position, the wires have to deal with the Z Amps, possibly for short intervals, and possibly smoothed out from battery to ESC by caps, but especially the copper wires (windings) within the motor have to take it.
If you now (to keep the example simple) double the Voltage (2x), you (approximately) double the current and produce about 4x the (max) Power (at full throttle). So now your bursts need to be shorter (4x), but there is more current(2x) in such a burst, which leads to losses especially within the copper windings within the motor (the diameter of the windings is still the same). You will notice that also, that the motor is heating up when running.

So trying to summarize in short words, higher voltage (for a given motor/prop) leads to higher current (but for shorter bursts) within the wires and therefore higher losses.

This is also the reason, why we are messing around with the motor KV to get the "right" motor for a given propeller and a given voltage. If you imagine a copter that would hover at 50% throttle, doubling the voltage would mean that it would now hover at 12,5% throttle (which is practically not flyable), assuming that the throttle stick position is linear to the power output. So if your copter flies (well) with 4S and is designed for that, it will possibly also fly well with 3 (if there is enough power left), but you will most likely not get it in the air with 2S. With 6S it will already be close to a rocket, but with 8S you can smell the copter before you see it.

best regards
Ferdinand
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Joined Jan 2010
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 No, I am sorry.

Whatever voltage you use, the C-rating is dependent on how long you fly, so if you have two copter that fly for 60min, one with 3S, and one with 6S, your load on the batteries is the same. It is a 1C application. (The battery for the second copter will have doulbe the cells, but with half the size, so if your amps draw is cut down by two, you gain nothing, because your cells only have half the capa).

best regards
Ferdinand

i am not sure in anything until i order and check. :(,maybe someone here have some friends in moto-sports where they use them a lot

So this is a world record for your own requirements? I suppose I could make thousands of world records be that the case. I find it funny that you took EndOfDay's idea for the battery pack and then claim to have a longer duration flight than him based on some arbitrary rules.

Having not read All of the posts in this thread prior to registering here, I was not aware that apparently there has/had been some cross pollination .. so to speak .. with EOD's RcGroups thread.  He as spawned great interest and innovation in making multi-rotors more efficient.  And with that .. of course comes .. Records!

So unlike the annual HK Beerlift contest, this flight duration records business is probably about due for some collaborative efforts to suggest some standards by which these records might be compared.  Further .. even the Beerlift has established Classes divisions.  As an example .. is an altitude record of 8,500 feet comparable with a record of 8,500 Fod?  Nope .. cause the historic Danish Foot (Fod) is 330.5mm .. the English foot is 304.8mm.  Amazing the stuff you learn watching the Woodwrights Shop ehh.

Whilst my example above is obviously absurd, it does point out the need to have some commonality in goals for these record setting endeavors now becoming more commonplace.  Even DJI is in the game .. flying at 19mph for 28 minutes with their latest commercial offering.  300-350 Commercial Class I guess .. time and distance .. ehh :-)

I found this Blog looking for a reasonably priced auto-pilot .. the APM 2.5 looks to be my prime candidate .. records or not :-) .. Cheers!

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