[werk_ag]

Hi,

The PV panel shown in post #6 looks as if it is a "real" crystalline silicon panel, but beware that many cheap "solar garden lights" use amorphous silicon panels which have several potential "issues":

Firsly, amorphous panels detect mainly visible radiation (light), whilst crystalline panels detect about as much also in the (near) Infra-Red band (as is required, I believe, for a correct watts/m2 value). Amaorphous panels may give a value nearer to a "Lux" measurement.

Secondly, amorphous panels are said to "age" (lose sensitivity) particularly in their first few hundred hours (which may be more of an issue for a product manufacturer than a Home Made system).

Thirdlly, I have measured a few amorphous panels which have had a relatively high reverese leakage current which might affect the accuracy/sensitivity of the measurement.

Hi Alan

You are absolutely right. During my tests I discovered it by the hard way... testing a lot of different kinds of cells. Some of them, as you said, are not suitable for this job, specially the "amorphous" ones.
Its output current is very dependent on the angle of incidence of light, producing bad results at low angles.