PV Gap

Ernest Said:

Solar-powered calculator vs battery-powered?

We Answered:

My Casio, which is both battery and solar, works quite well with a dead battery (so long as the lights are on). I would think this would be better than relying on a battery only version, as you can never be sure the battery will last. Even a new battery may have been sitting on the shelf for years before you got it.

Eileen Said:

can a solar panal of a calculator power a flashlight buld?

We Answered:

No. A small flashlight bulb like a size 222 requires about 2.25 volts and 0.25 amperes. Calculators need a couple volts but only about 0.000010 amps. High current (crystaline silicon) cells make about 0.3 volts, each, so you would need 7 or 8 cells n series to make the required 2.25 volts. The area of the cells is what determines the peak current. A square inch cell can produce 0.2 to 0.5 amp, depending on the cell quality.

You might think about replacing the lamp with a white LED. These need about 3 volts, but only 0.02 amp for full output and give a white light (at lower intensity) at much lower currents. So small area cells will light these.

--
Regards,

John Popelish