Electric RC aircraft are not known for long flight times, with multirotors usually doing 20-45 minutes, while most fixed wings will struggle to get past two hours. [Matthew Heiskell] blew these numbers out of the water with a 10 hour 45 minute flight with an RC plane on battery power. Condensed video after the break.
The secret? An efficient aircraft, a well tuned autopilot and a massive battery. [Matthew] built a custom 4S 50 Ah li-ion battery pack from LG 21700 cells, with a weight of 2.85 kg (6.3 lbs). The airframe is a Phoenix 2400 motor glider, with a 2.4 m wingspan, powered by a 600 Kv brushless motor turning a 12 x 12 propeller. The 30 A ESC’s low voltage cutoff was disabled to ensure every bit of juice from the battery was available.
To improve efficiency and eliminate the need to maintain manual control for the marathon flight, a GPS and Matek 405 Wing flight controller running ArduPilot was added. ArduPilot is far from plug and play, so [Matthew] would have had to spend a lot of timing tuning and testing parameters for maximum flight efficiency. We are really curious to see if it’s possible to push the flight time even further by improving aerodynamics around the protruding battery, adding a pitot tube sensor to hold the perfect airspeed speed on the lift-drag curve, and possibly making use of thermals with ArduPilot’s new soaring feature.
A few of you are probably thinking, “Solar panels!”, and so did Matthew. He has another set of wings covered in them that he used to do a seven-hour flight. While it should theoretically increase flight time, he found that there were a number of significant disadvantages. Besides the added weight, electrical complexity and weather dependence, the solar cells are difficult to integrate into the wings without reducing aerodynamic efficiency. Taking into account what we’ve already seen of [rcflightest]’s various experiments/struggles with solar planes, we are starting to wonder if it’s really worth the trouble.
45 thoughts on “Electric RC Plane Flies For Almost 11 Hours”
If you’re gonna do that to your LiPo’s, you might as well just use disposable batteries. Higher energy to weight and it’ll be cheaper than destroying expensive lithium cells every flight.
I was thinking the same thing… but which battery chemistry would you use for better energy density, silver-oxide?
Part of the trick here is the custom Li-Ion pack. LiIon packs more power per gram than LiPo, but it has (per cell) a lower max current delivery. Here, he’s gotten the planes efficiency high enough that it cruises on what the batteries can put out, which lets it run a long time.
There’s some clever optimization going on here. And all that with a stock, if slippery, airframe. Pretty cool.
Shouldn’t it be the other way around? LiPo has greater power (higher current), but less energy per gram, Li-Ion has more energy but lower power (lower current).
I’ve been active in the electric RC revolution from the beginning. Lipos and brushless motors were huge gamechangers. I also used to think the same thing but recently changed my mind after obtaining some of the more recent lion cells. Yes, Lipos do have higher current capacity but there have been huge gains with the latest lion cells. Lipos are still used in most RC applications when high loads are needed but lions are being used more and more for moderate or endurance type apps.
Check out the specs on this 21700 cell https://www.18650batterystore.com/collections/21700-batteries/products/molicel-p42a. These aren’t hyped ratings either.
Chris Barth, when you say you were there from the beginning, do you mean ten years or something else. The first electric car was in 1833, the first wave of electric RC was in 1975.
Chris: that’s about 12C rated cell, while modern LiPo batteries go up to 280C which is absolutely ridiculous – you could pull a thousand amps out of the battery.
600 kV motor, or typo?
“kV” is a “velocity constant” in hobby motor speak. It means that it does 600rpm for each volt applied to the motor (with no load)
so not 600kV but 600r/m/V (or 600rpmpV for yanks/brits/whoever uses a letter for division :-P )?
but why kV?
It should have been K/V (1000 / V) but RC folks just omitted that slash for weight reduction reasons.
Makes sense, don’t you say?
It’s kV — but k is for constant. It’s the proportionality constant between RPM and voltage.
5 V and 2000 kV motor, it turns at 10,000 RPM.
It should be Kv actually. There’s a bunch of motor constants that are all denoted with a K and some subscript letter V, T, M… etc.
It’s math notation. It’s literally ‘K’ subscript ‘v’ but Kv is close enough on internets.
>powered by a 600 kV brushless motor turning a 12 x 12 propeller. The 30 A ESC’s low voltage cutoff was disabled
yeah… 600.000V makes no sense at all. maybe 600W?
The ESC’s are rated for 30A and a 4S accumulator has nominal voltage of 14V (? not sure).
kV is RPM per Volt of Back-EMF. ie, the voltage the motor will produce when freewheeling. 600kV will be a relatively slow motor, but very torquey, if I’m remembering right
no typo, but a different kind of Volt: http://learningrc.com/motor-kv/
Admittedly when I came across that notation a few years back, I initially thought KV, as in kilovolts, needless to say, I was scratching my head for a few minutes before looking it up.
Damn confusing, especially for those with a prior interest in high voltage equipment. Note, those motors don’t need many volts to spin quickly, but they can draw a lot of current.
Why not use hydrocarbons for power?!
I’ll just leave this here: https://en.wikipedia.org/wiki/The_Spirit_of_Butts%27_Farm
TLDR: 5kg plane (fueled) -> 38h transatlantic flight
Because it’s not the future. Besides, several planes ended up in the sea before one kept going long enough. They just aren’t reliable.
Which is why the US military uses them for all of their small drones? There’s far more energy per gram to extract from hydrocarbon fuels than from batteries.
Synthetic gasoline is the future.
For those not familiar with motors. Kv constant explained:
Pretty neat, maybe a folding prop would help the aerodynamics a bit too. Still impressive.
thx for the link – interesting read.
but why don’t you, Eric, “they” (as in RC enthusiasts) type K_v instead of Kv? Isn’t the underscore a quasi standard for expressing subscribed letters in scientific formulas (in normal text without special formatting)?
It would prevent a lot of potential confusion.
It would but that’s not how it’s done. Doing something nonstandard introduces a lot of real confusion.
Thanks! Added the link to the post for clarification
Whats the big deal here? that this thing runs from battery instead of solar panels and solar power is soooo bad? You know you can get paint these days which acts like a solar panel and just paint it on the plane to harvest energy
“you can get paint….” is a bit dubious. The paint you are referring to isn’t remotely on the market yet, and the paint is only about 20% efficient.
20 % efficiency of a regular solar panel or 20% of the available solar energy which is about all a solar panel gives in the first place. The other 80% is reflected back and or converted to heat which reduces the output of a solar panel anyway. There are panels that have cells on both sides now to increase output but kind of hard to make that work in this app. for sure a lose of dynamics.
You could always use the bare solar panels as a physical part of the wings and not just stick them on top. Add spars and braces above and below, then shrink wrap the whole thing in clear plastic. Even perhaps coat them in clear silicone sealant to make the aerofoil shape, although that may prove too high density.
You can buy, “offcuts” and broken panels online pretty cheaply. Stick them to a thin rubber sheet and solder them together with some enameled copper wire, then you could wrap them around the curved shape of the wing, probably cheaper and more electrically efficient than buying the new “flexible” solar panels.
No paintable solar, yet, but there are flexible solar panels one can buy today, allowing perfect aerodynamics:
The challenge to fit them onto a wing is still left, of course :-)
I have no dog in this fight, but 20% efficiency in a solar panel is pretty damn good. The best solar panels that you put on the roof or about 22 1/2% efficient.
I seem to recall from the very dim and distant past (early ’90s) that there’s a competition class for this? A work colleague was into it at a national level back then. Of course, battery tech has come a -long- way since then!
Need to try this with a Canard design.
If we are playing “what about”, then what about making a secondary recharge aircrafts that allow an unlimited range for it? Or even doing a battery swap mid air? I’m thinking magnetic terminals that allow easy connect/disconnect with poor alignment.
Awesome project, loved the landing. It would be hard to slow it down with all that weight but he did a great job . Glad the video wasn’t as long as the flight :-)
Well done. Thanks for the inspiration. Interesting to note that as the battery voltage drops the current needed to fly goes up. I think that a lot of up draughts helped achieve that flight time but still a great achievement.
I think this is going to be the next frontier, honestly, and maybe we’ll see it get started in the next 5 years. It’s very hard, though.
Personal bet: more instrumentation / sensors on the plane will be key. Full-scale / human-carrying glider pilots have windspeed + altimeter that lets them figure out their total energy. They also have a telltale or “yaw string” that lets them know when they’re side-slipping in turns. Most model planes lack even these basics.
Thermals are also a hell of a lot bigger and more stable up where full-scale gliders fly. The stuff under 100 m is significantly trickier: turbulent and transient. The models simply have to be that much smarter.
Whoever wrote this arrival has never flown a hobby RC plane. 2 hours? Try 5 to 10 minutes… that the typical run duration of hobby grade electric model aircraft.
Some people have achieved an hour+ in custom setups build for duration challenges but if you walk into your local shop and buy something from E-Flight or Horizon Hobby you are not getting anywhere near that.
Agreed, i had to build from scratch but it ended great. Custom made rc wing with 90min flight time (depends which battery i out on)
I use it for long range (mountain) surfing
Hate to cause a wake up, but, you can. Ever hear of slope soaring? My personal best was 3 hours
You had good reason to be dancing for joy, very awesome.
Why didn’t you use dilithium crystals, like on the enterprise? Oh pleeeeease. All these “you should have done it this way” comments are just pulled out of your left ear. Just appreciate what the man did at face value. Well done, dude!!
I so agree. There are probably many projects not posted because of a fear of facing the firing squad of comments.
Well done thanks for posting.
could you fly one of these planes in straight line point to point? with gps programed in to controls?
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