On Sat, Jun 4, 2011 at 7:20 AM, RussellMc wrote: > > My idea is to use one of these solar cells ( > > http://futurlec.com/Solar_Cell.shtml), probably the 6 or 9 volt, plug i= t > > into a small buck switching regulator and charge a 100-200mAh Li polyme= r > > 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.) > > That's rather disappointing :( Looks like I'm going to go with inductive charging then. I'll just make a small pad to put the device on so it can charge. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .