“Be kind, for everyone you meet is fighting a hard battle” - Often attributed to Plato but likely from Ian McLaren (pseudonym of Reverend John Watson)

## Saturday, July 06, 2013

### Solar sells - anything

But what about the sun? The Amazon page for the charger lists its dimensions as 5" L X 1.5" W. Using the free and terrific Tracker Video Analysis software (which works just fine on jpegs) I determined that the "high efficiency solar cell" is about 1.46" X 0.85". This is $8.00*10^{-4}{m}^{2}$. I'll also assume the cell to be 20% efficient. I'll use $350\,{\frac {w}{{m}^{2}}}$ as a good average for available insolation in my area. That yields a charging rate of about $8*10^{-4}*350*0.2 = 0.056$ watts and a time to charge to capacity of $2.05/0.056=36.6$ hours. Others at various review sites cite (sites cite? I like it) two days, which doesn't seem unreasonable. On the web site video, they show the unit being charged under a table lamp. Umm... good luck with that.