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Jan 23, 2019, 03:14 PM
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Bixler 3 solar powered


Hello, RC ppl,

my colleague @ work invited to my new "old" hobby. Been building "balsa kits" from scratch - literally from plain board, no laser cuts etc, when I was young and beautiful. Now it is only beautiful left

Looking forward to buy Bixler3
https://hobbyking.com/en_us/h-king-b...-1550-pnf.html
(My colleague flying Bixler2 FPV)

After watching 100's of videos how the aircraft is awesome, found that it can fly ~20 min on 1 battery

I'm fan of renewable energy sources - eg. driving prius plug-in, love idea of solar pannels, etc.

My question
https://www.aliexpress.com/item/BUHE...AbTest=ae803_3

Maximum Power: 0.5 W
Operating voltage: 1.5 V

If you connect lets say 10 in parallel (Should be enough space on the wing on Bixler 3), will generate ~15V, 3A (15V/5W) , will be sufficient enough to recharge battery during flight - eg. boost climb, then glide

Please share your experience and knowledge, as this I did currently found only 3 successful projects on Youtube... Maybe it is wasting of my research time and effort, who knows,...
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Jan 23, 2019, 08:42 PM
yank and bank!!
probably 99% of solar plane experiments fail miserably.

And those solar cells probably do not put out anywhere near that much power...... AND if you connect 10 of them in parallel the output voltage will still be 1.5V even IF the specs weren't bull.
Jan 24, 2019, 01:34 AM
Bombs away! Err...landing
Ira NZ's Avatar
Quote:
Originally Posted by Auri

Maximum Power: 0.5 W
Operating voltage: 1.5 V

If you connect lets say 10 in parallel (Should be enough space on the wing on Bixler 3), will generate ~15V, 3A (15V/5W)
If you put 10 in parallel you'll be looking at 1.5v, 3a, not 15volts 3 amps which would be 45 watts and certainly should be enough to fly on. But you'd need 100 panels for that.

I don't think a bixler would fly on 5 watts.
Jan 24, 2019, 08:38 AM
Wake up, feel pulse, be happy!
Piece's Avatar
Quote:
Originally Posted by Ira NZ
If you put 10 in parallel you'll be looking at 1.5v, 3a, not 15volts 3 amps which would be 45 watts and certainly should be enough to fly on. But you'd need 100 panels for that.

I don't think a bixler would fly on 5 watts.
100 panels and optimal sunlight.

A somewhat more viable approach is to fly a glider capable of squeezing lift from the tiniest thermals and use PV cells to keep its radio battery charged. A small launch motor and appropriate battery could be carried as well, and you may even be able to recharge the motor pack while gliding, but thermal activity and a razor-sharp, purpose-built airframe are going to be prerequisites. Such a plane could potentially fly for hours in good conditions even without any solar panels, so you'd be looking at extremely long flight times.

It pretty much boils down to that, honestly: any airframe that's efficient enough to make practical use of solar power will have absurdly long flight times if you skipped the solar panels, wiring, regulators, inbuilt airframe considerations, etc. and went with an equivalent weight of lipo batteries.

The smartest way to go, if you're only in it for the renewable energy factor (versus wanting an actual solar airplane), would be to build yourself a solar-powered charging station and use it to keep your electric models fed.
Latest blog entry: Jeti ESC resto-mod
Jan 24, 2019, 09:13 AM
Flying a Falcon or a 3D model.
fauconnier's Avatar
A very sedate plane need 70 Watts/kilogram to fly.
Solar panesl weight 15 g. / Watt. In the best condition , it's 66 Watt/kilogram; barely enough to transport the solar panels only.
Jan 24, 2019, 03:08 PM
B for Bruce
BMatthews's Avatar
70 watts per lb on a fairly light wing loading sport or light scale model represents a fairly good climb with the nose up at around 50 degrees. I've got two lighter weight scale ARF's I currently fly that are running at 60 watts/lb and they lift off and climb away comfortably and in a nice scale like manner at around 2/3's throttle. I hardly ever use the full 60 watts/lb in flight and rarely for takeoffs.

Normal expectations are for a sport model such as a Bixler to use about 12 to 15 watts/lb of model weight to just fly level at a speed a bit above the stall. Model sailplanes with better optimized wing shapes get by with more like 6 to 7 watts/lb of model weight to again fly level. Other light and efficient designs are ranked through that range.

But yeah, your numbers for the solar cells are wrong. Listen to what the others are saying.

You need more voltage than what the battery pack is rated for to force a charge. So right off the bat to charge a 3S pack you need to have 9 or 10 cells in series to get up around 14 to 15 volts. Call it 10 because the wing won't be facing the sun directly. And even then you may need 12 or more due to the angle of the wing to the sun in flight. But call it 10 for giggles.

But if you start with the larger 1W cell and series 10 of them you'll get 15W. But flying weight of the Bixler is 900gms or just under 2 lbs. And to do more than just barely fly level you'll need more than 28 watts. A VERY SLOW climb would result at around 25 to 30 watts/lb. So that means you need roughly 4 sets of the 15 watt string of 10 cells in series to provide enough power to fly the model in the most minimal manner imaginable.

But this could be a problem because each of the 1 watt cells is 200 x 100mm. And you need 10x4 of them. That's a hugely larger area than the wing of the Bixler.

And that would be why we use batteries to store the power for flying. If you really want to use solar power for this then buy a large panel to use as a power source for charging the batteries on the ground.
Jan 25, 2019, 06:33 AM
Flying a Falcon or a 3D model.
fauconnier's Avatar
Quote:
Originally Posted by BMatthews
70 watts per lb on a fairly light wing loading sport or light scale model represents a fairly good climb .
I wrote 70 Watt/kilogram.
Jan 25, 2019, 07:11 AM
Registered User
Auri
Yes there are solar powered model planes that fly reasonably but they are pretty specialised both aerodynamically and structurally to do it.
Unfortunately with the available solar panels a 'solar' Bixler is not a practical proposition.
Jan 25, 2019, 03:24 PM
B for Bruce
BMatthews's Avatar
Quote:
Originally Posted by fauconnier
I wrote 70 Watt/kilogram.

DOH! Ya got me! Sorry....
Jan 26, 2019, 09:59 PM
Sokol
JureZ's Avatar
Auri,

just buy the Bix, and a few extra batteries, learn to fly and land safely , and when you have enough experience, take your plane to slope soaring.

The bix will slope soar for a whole afternoon with a single battery charge, in the right location, with the right wind condition.
Accompany this plan with the training on a flight simulator such as picasim (free).

After this, reconsider the solar plane option, when you are flying at another level, maybe next year (or in two, or three...).

Another model plane you may consider is the Radian glider.


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