Using solar panels to trickle charge flight batteries? - RC Groups
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Aug 04, 2001, 05:20 AM
Time wounds all heels.

Using solar panels to trickle charge flight batteries?

I have seen several interesting solar panels recently. One, for example, makes 6v 100mah in full sun. Another makes 5000mah .48v. The sizes are roughly the same, and both weigh in at around .2oz per panel. Some even come with adhesive backing at .26oz.

Is it feasable, or plausible to recharge batteries in flight? I posted here, instead of in model science because I thought that extending the life of a reciever pack might be of most interest to duration minded flyers. (although I may duplicate thread there, since its kinda science related, too.)

(start with the hissing and catcalls from the peanut gallery)
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Aug 05, 2001, 03:51 AM
Model Designer
keven64's Avatar
Hello watersharer,

Just one question for you.
Are you charging the nicad at a rate that will only put into the battery what is being taken out ?
I suppose, ( My opinion ), that if you use a tiny rx battery, say 50mah, and a couple of the solar panels to provide slightly more voltage than the nicad, it might be feasible to fly using the solar panels to power the radio, the nicad being there to start the process, and to provide adquate power ( ? )to get the thing down if the clouds arrive . . .
Even with solar cells, you never get something for nothing - experimentation will show what the trade-off is !

I have two ( rather heavy )solar panels somewhere . . .
I Will test their output voltages under load.

Aug 05, 2001, 03:58 AM
Model Designer
keven64's Avatar
Hello again

I tested them right away;
they are both the same and produce 1.103v in hazy sunlight.
I'll need another four . . .

Aug 05, 2001, 11:16 AM
ὅπερ ἔδει δεῖξαι
Gerald's Avatar
If I recall correctly a single solar cell typically produces about 0.45V at rated load. One nice thing about solar cells is that you can short them without damage so there is never any fear of overloading. For charging batteries you need to select enough cells to connect in series to produce a little more than the full charge voltage of the battery. For NiCd this is about 1.6 - 1.66 volts per cell. So 4 solar cells would make about 1.8 volts.

The heavy weight of solar cells far outweighs (pun intended) their usefulness in-flight on R/C models. But a ground based solar panel would be great for in between flight charging. Now that you've reminded me, I've got a little 1' square solar panel that I used to use for trickle charging my car battery when it was to be sitting a long time. I oughtta see if that will work for charging my field battery while out flying.
Aug 05, 2001, 11:32 AM
Time wounds all heels.
The solar panels I am referring to are 6v@100mah in full sun.

See them at , under the modules section. They even have a section for model aircraft panels.

And you could fly five panels per ounce. They weigh .2oz per panel.

The biggest problem I see is a model with enough wing area to place them all, and a wing loading light enough to be powered by 6-8 of these panels.

[This message has been edited by watersharer (edited 08-05-2001).]
Aug 05, 2001, 12:04 PM
ὅπερ ἔδει δεῖξαι
Gerald's Avatar
Hey, those are the lightest modules I've ever seen! You'll probably have to design your own airframe to use them for propulsion power but I bet they'd work great for just powering the electronics of a typical sailplane. Only a very small flight battery would be required so you'll make up the weight gain of the panels in the weight savings of the smaller battery.
Aug 05, 2001, 02:28 PM
Registered User
Kevin Murray's Avatar
Water - Graupner used to sell a solar powered motorglider here and may still sell it in Europe.
It's called the Solar UHU. There was one for sale on EBay yesterday. I wanted it but was out-bid at the last second.

I don't think the UHU will but there are sailplanes that can sustain very long flights on very small packs. Search the web, you'll find sone interisting sites. You'll need Bable Fish or some other translator, or at least I did.
Aug 08, 2001, 03:36 AM
Model Designer
keven64's Avatar
Wow . . .

Well, Solar Power for the masses now ?!?

Aug 08, 2001, 04:02 AM
ChrisP's Avatar
Sun ?

What's that ?

If you have a design to charge my batteries with a miniature windmill, it would be far more useful to me.

Or something rain powered ?

[This message has been edited by ChrisP (edited 08-08-2001).]
Aug 08, 2001, 04:04 AM
Model Designer
keven64's Avatar
Hello again,

Watersharer, five of these panels,( those you mention ) would produce a power 'pack' equivalent to a five cell nicad and a half-amp rating. That is not to say that it will be = to a 5-cell 500AR battery.

There are certain possibilities with this idea, and ten in parallel would certainly be a viable avenue for a project. A large powered glider type, with the wing almost, if not completely covered with the panels, would certainly power a motorglider, though the voltage would be a little low.
Perhaps stick-type construction like the old free-flighters ?

Maybe use a 4.8v S400 for power with a Gunther prop ?

From their info on the website, A wing completely covered in panels, with tip dihedral, would have a projected span of 53 1/8". Chord would be 7 1/8". The flat centre would be three panels wide, with another three behind those - with the tips each having a span of 10 5/8" ( the length of the panel ) with two panels one behind the other.
No need to carry cells with this - power the motor directly through an ESC . . .
I think I would carry a small rx nicad though . . . !

Who will be the 1st to offer me sponsorship ? Hehehehe
$240, though not excessive for the items in question, is a little too much for me to play about with . . .

You fancy trying it yourself Watersharer ?
You like to experiment !

Oct 27, 2009, 12:35 PM
Registered User
videocruzer's Avatar
I ran the numbers on charging my 8s A123's via solar.
about 2200 bucks of solor gear would charge my packs under 30 minites.
this was based on the solor panals that you can roll up like a sleeping bag.
12-18 months and this price should be more then 50% cheaper.
Oct 27, 2009, 05:28 PM
Stress Be Gone
GBR2's Avatar
I went to the site: and all I saw was listing for all kinds of stuff. What exactly is the website that has the 6V@100ma solar cells?
Oct 27, 2009, 05:57 PM
The King Moonracer of balsa.
Windependence's Avatar
This months issue of Soaring Digest has an article on how to do just this. Solar panels mounted on the wings keep the Rx battery charged for all day flying. I read another article on how to do this about a year ago and if I can find it I will post a link later. For now here is the link for the Soaring Digest one

Oct 27, 2009, 06:35 PM
Registered User
I know that this question is just about charging the little batteries, but it is also possible to power motors for takeoff too.

Full size versions:
If you dig around on the website, you can see a photo of an RC version

And a UAV, that was famous but I don't think it worked:

possible vaporware:
Oct 27, 2009, 06:53 PM
Registered User
Dennis Everett's Avatar
"astro" Bob Bouche made a solar powered rc plane back in the 70's , operation sunrise , i think it was called , got as high as 17000 ft i believe , ............Dennis