Went for our long distance flight attempt today, flew a test flight with a 6S 2600mAh LiPo and then put in the 18650 batteries in, the log unfortunately shows both flights as I forgot to reconnect so I have calculated the time and total distance from the launch of the second flight to the landing. 

Basically we did a 300m diameter Loiter for most of the flight, biggest problem was the phugoid motion of the plane losing height on every downwind leg and having to regain the lost height on the upwind leg using precious amps to do so. I tried just about every parameter to tune the plane better throughout the first hour but could never get it to behave.

Special thanks to the devs (especially Tridge and Paul Riseborough), to Steve B. for assisting and UAVDS for making it possible


Plane: Super Sky Surfer

AUW: 3078g

Motor: Maytech MTO3548 790Kv

Prop: APC-E 9x6

Batteries: 6S4P NCR18650b 25.2V, 13600mAh

Battery weight: 1172g

AutoPilot: APM2.5, APM:Plane v2.78.

Weather: Calm (0-4km/h), clear blue sky, 26°C. Altitude: 1668m ASL

Time flown: 126m 53s

Total Distance flown: 116.475km

Calculated consumption on nominal capacity: 115mAh per km (will update after recharge).

Estimated current draw: 5.2A average

Lowest voltage on pack 18.0V

Average speed: 55km/h

Droneshare: http://www.droneshare.com/view/bfgodhs

Tlog: https://db.tt/UfVPiyBE  (12MB)

KMZ: https://db.tt/1Tmzim1W  (3MB)

Views: 3938

Comment by Walter Smit on February 11, 2014 at 4:28am

Hi Graham

Can you please share more detail on your battery setup? I have a bunch of 18650s (protected 3400mah) lying around...

Thanks!


Moderator
Comment by Graham Dyer on February 11, 2014 at 5:36am

Nothing very special except they're unprotected cells - spot welded in 6S2P form (6800mAh), each with 6S balancing tap, used 2 of these in parallel, one in the front under the canopy and one in the fuselage under the CG.

Comment by Tommy Larsen on February 11, 2014 at 5:56am

That would be a 13600 mah :)


Moderator
Comment by Graham Dyer on February 11, 2014 at 5:58am

Changed, thanks :)

Comment by Walter Smit on February 11, 2014 at 6:10am

@Graham - welding protected cells - I would rather not :-) I would rather try to get some battery holders and arrange in whatever format I need, so that I can still charge (and use) my cells in my other devices (torches). Or am I being silly and should just buy whatever Lipos I need? 


Moderator
Comment by Graham Dyer on February 11, 2014 at 6:40am

I'm not sure what protection these 'protected' cells have, it may be something one can just remove?

I would never use battery holders, I have visions of the problems I had with AA cell holders, the risk of a broken connection is just too high not to mention the electrical resistance. Spot welding uses a very short high power surge to weld tabs onto the cells, just about every laptop's battery is prepared this way.

Some people have just soldered copper braid onto the cells to join them, they solder very well in fact.

Comment by Wojciech Batog on February 11, 2014 at 7:24am

This seems to be somehow inefficient...
Why 6s battery? it seems like a 4s would be a better choice for this motor... Why such a small prop? Why this motor anyway?


Moderator
Comment by Graham Dyer on February 11, 2014 at 7:44am

Good questions, Wojciech. This was a "see if I can" rather than a meticulous record attempt, we have other goals, distance/duration is just one of them.

The largest prop that can fit on this plane without modification is 9-10", however lower Kv motors for a larger prop and motor adapter plates are on their way, should be here next week. I'd like to use the highest practical cell count, lowest Kv motor and largest practical prop I can.

I'd say 115mAh per km is VERY efficient, the other two 100+km flights I know of used <160mAh per km. Ours will probably be even lower as I estimate I only used 12000mAh so that's 103mAh per km!

This 3kg plane only needed about 125W average over 2h06m!

Comment by Walter Smit on February 11, 2014 at 7:54am

Thanks for the thoughts on battery holders Graham - I am going to abandon my idea of "recycling" batteries I already own. I really dont want hassles with broken connections!

Comment by Wojciech Batog on February 11, 2014 at 8:34am

mAh per km is not a good measure since voltage is also a factor...
Wattage gives you a better idea of efficiency...
Anyway taking into account that You were flying in constant bank, thats not that bad ;)

But when you think that for instance a Human Powered Aircraft uses 175-220 for sustained flight ;) and it weights 80kg and has 25m span...

Anyway I think a faster aircraft would give you more km per W :P

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