> My idea is to use one of these solar cells (
> http://futurlec.com/Solar_Cell.shtml), probably the 6 or 9 volt, plug it
> into a small buck switching regulator and charge a 100-200mAh Li polymer
> cell.
>
> Reasonable?

Theory is goodish.
Practice is not good if ONLY artificial light is available.

In good bright room light (100 -1,000 lux range) a PV panel will make
0.1% to 1% of rated output.
Usually closer to 0.1%.

I just tried a fairly leading edge small panel (as used in SNS Mini
light) rated at 2V 150 mA at 1 sun.
It gave under  0.1 mA loaded on a table top in a reasonably well lit room.
0.1 / 150 =3D 0.07% :-(.

Add a whiff of daylight occasionally, even quite diffuse, and you will
get much more output.

Full sun =3D 100,000 lux.
Touching the surface of typical modern LCD screen at full brightness =3D
300 lux =3D 0.3% sunlight !!!

FWIW the PV panels on that page are priced at less than 3 x the Chines
wholesale price ex factory in moderate volume.
However, they all seem to be epoxy sealed, which would lead to a short
lifetime if exposed to lots of sun. OK for indoor use or occasional
portable use etc. Put them in a path light or shed light or powering a
piece of equipment with 24/7 outdoor use and they will die in a year
or two. Maybe less in some cases.

Those are very fine for playing with and if the above limitations are
OK. For serious outdoor use look for P.E.T. encapsulated panels (same
plastic as used for most softdrink bottles.)


         Russell
--=20
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