Hi,

We, Aerospace Dept, are working on an ornithopter like the one in the link below:

http://homepage2.nifty.com/smark/Sord55VE.htm

Battery used: Hyperion CX G3 25-45CLG325 7.4V180mAh

It’s the battery number six from the bottom of the list found in the table in page 1 in the link below:

http://media.hyperion.hk/dn/g3lipo/G3-Specs-EN.pdf

Specs of the Ornithopter:

width
95.0
cm
length
112.0 (70.0 except for tail)
cm
weight
102.0
g
Total flight weight
119.0
g

We want to use thin film solar cells to recharge this battery while the ornithopter is flying.

Can you reply me ASAP

Thanks!

 

There's no point to doing that. You won't get enough power to fly so the battery will still be drained, possibly a little slower, if you ignore the weight of the solar cell. However the extra weight will require more power and therefore reduced flight time overall.

 

There's no point to doing that. You won't get enough power to fly so the battery will still be drained, possibly a little slower, if you ignore the weight of the solar cell. However the extra weight will require more power and therefore reduced flight time overall.

The ornithopter will fly with battery, and the solar cell will charge the battery.

What is complicated in this!!

The solar cell at Silicon Solar is ~ 1.9oz (53.864094 grams) and maybe there is lighter cells.

What I need to know is Which solar cells to choose:

Flexible Solar Battery Chargers 7.2V 100mA

or

Flexible Solar Battery Chargers 7.2v 200mA

or

Flexible Solar Battery Chargers 15.4v 200mA

and Do I need a charge controller ?

 

You are planning on using an old Generation 3 (G3) Li-Po battery.
I have my local hobby store ordering for my electric RC airplanes new Generation 4 (G4) Thunder Power Li-Po cells from Horizon Hobby that are much better. Thunder Power has hundreds of Li-Po batteries.

My airplanes fly efficiently for a very long time. Your flapping thing uses a lot of power, almost as bad as a helicopter.

 

You are planning on using an old Generation 3 (G3) Li-Po battery.
I have my local hobby store ordering for my electric RC airplanes new Generation 4 (G4) Thunder Power Li-Po cells from Horizon Hobby that are much better. Thunder Power has hundreds of Li-Po batteries.

My airplanes fly efficiently for a very long time. Your flapping thing uses a lot of power, almost as bad as a helicopter.

From this link:

http://www.thunderpowerrc.com/PDF/ThunderPowerRC-Pricing.pdf#page=2

TP250-2SJPL2 is the nearest one for what I need, correct ?

 

But its heavier than Hyperion batteries.

http://media.hyperion.hk/dn/g3lipo/G3-Specs-EN.pdf

Hyperion battery "LG325-0180-2S" is 13.55gm and Thunder Power "TP250-2SJPL2" is 17 gms

Do you know Thunder Power batteries 180 mAh lighter than those ?

 

But its heavier than Hyperion batteries.

The flapper is much heavier than the battery.
The Thunder Power is 250mAh, the Hyperion is only 180mAh (28% less).
The Thunder Power has a connector, the Hyperion doesn't.

 

and Do I need a charge controller ?

Not for any cell you can get off the ground. It would be a concern for the higher voltage panel. With a blocking diode, the 7.2v panels will deliver about 6.5 v to the battery and this will not take it to (or past) full charge.

Your problem is power-to-weight ratio. I doubt the ornithopter has much payload capacity and the cells you're looking at weigh almost as much as it does. Worse, they'll only supply a fraction of the power needed. They'll essentially be dead weight.

 

Thin film solar cells(amorphous silicon) require about 2x the surface area to produce the same amount of power as the more efficient crystal silicon cells.

Research your solar cell needs a little further and plan on using a higher voltage than the battery gives out to produce a faster charge rate. You might think about using just the cell material and not a 'complete' unit since that doubles or triples the weight of the cell.

 

http://cgi.ebay.com/ws/eBayISAPI.dl...fae1141&itemid=170449551910&ff4=263602_263622

Just one of thousands of sellers of basic solar wafers. These will be .5 volt wafers and can be further cut down to give .5 volt units with lower amperage that can then be wired up for a higher voltage. weight will be minimal and mounting methods will be controlled by you. You can also control the size of the solar cell you construct yourself, to better take advantage of the surface layout of your flying machine.

 

There are better solar cells these days at UniSolar, Ascent, MiaSole, Etc.

 

Can this 7.2V 200mA Flexible Solar Panel charge the battery ?

http://www.siliconsolar.com/flexible-solar-panels-6v-051293-p-501001.html

 

You'll have to prove it to me then. Uni-solar thin film flexable solar panel, the ones that claim better efficiency because of red, green, and blue layers that capture more of the sunlight blah blah blah.

Running the numbers with my 'amorphous thin film panels from five years ago. I get 60W from 1404 sq in. They get 68 watts from 1728 sq inches.

That ain't improvement of anything but the advertising message. If you've got numbers and a source of verifiable info I'd be interested in seeing it, but until then I call "Sullbhit" on the better than they used to be claim.

crystalline silicon cells are still 2x as effective at current delivery on a sq in. basis. I should know, I have the less efficient amorphous cells.

 

Your "7.4V" Li-Po battery is fully charged at 8.4V so the 7.2V solar panel will barely charge it. You also need a diode in series which drops even more voltage.

 

The ornithopter will fly with battery, and the solar cell will charge the battery.

What is complicated in this!!

The solar cell at Silicon Solar is ~ 1.9oz (53.864094 grams) and maybe there is lighter cells.

What I need to know is Which solar cells to choose:

Flexible Solar Battery Chargers 7.2V 100mA

or

Flexible Solar Battery Chargers 7.2v 200mA

or

Flexible Solar Battery Chargers 15.4v 200mA

and Do I need a charge controller ?

Looking at those panels you listed, and comparing them with my panels on a watt/sq. in. basis, I find they all give approx .04W per sq in. Compared with the crystalline solar cell wafers at the eBay link I gave they are half as efficient on a watt/sq. in. The crystalline ones check out at .08W per sq. in.

anyone can verify this. take the wattage of the panel(V*A) and divide it by the product of its width and length in inches. There will be small variance, but overall you (or anyone) will find the crystalline silicone is twice as powerful, wattage wise, per sq. in.

Any application where surface area is limited should use the more power dense crystalline silicone cells(wafers)

 

If you overcharge a lithium battery then it might catch on fire. You must limit the charging voltage per cell to no more than 4.20V and disconnect the charger when the battery is fully charged.

But your solar panel has a voltage that is much too low to charge the battery and the current is probably too low to power the flapping thing.
Have you measured how much current is used by flapping?

 

Any application where surface area is limited should use the more power dense crystalline silicone cells(wafers)

In this application, WEIGHT is far more limiting than surface area. So power-per-weight is the more important metric. Crystalline might still win?

OK, surface area is limiting also, but the cells won't supply more than a small fraction of what the bird needs using either cell technology.

It'd all make WAY more sense to leave the charger (a big solar panel) on the ground with a spare battery under charge, and fly the bird with as little payload as possible. You could even then calculate how big the panel would have to be to keep up with the bird, for almost continuous flight except for battery changes.

 

A real bird eats a lot of food to make energy to fly.
The toy flapping thing (they are sold in hobby stores) uses a lot of battery power to fly.

My electric radio controlled model airplanes use aerodynamics to fly with very low or no power or use a lot of power to climb straight up like a rocket.

 

AudioGuru: Have you measured how much current is used by flapping?

A maximum electric current to be able to take out from LipoBattery is C*mAh/1000.
Lipo of Max BurstDischarge 40C 250mAh ---
40*0.25=10A
10A is Max Discharge current

 

or 6.3 Amp for the battery mentioned before, 180mAh, 7.4 V, 25-45C