This thing was 99p. I thought, wow, that's a big solar panel and three LEDs for 99p. How can they do that?

A simple dissection shows that the circuit is very simple. There's a lithium battery, CR2016, 3V. Famed for its rechargeable nature. eek A PCB switch mounted on a small piece of PCB. And three LEDs in parallel... no limiting resistor, although not usually required as the lithium cells have such a high ESR that they limit the current sufficiently.

But wait, how does the solar cell come into it?

Well, it doesn't... or at least, nothing is connected to the panel. And in fact, the torch does not work with the battery disconnected.

So, I thought, why would they bother with such a large solar panel? Those panels would be quite expensive - about £3 to £5 each - and there's no way they could sell these at 99p. Then I looked carefully, and I noticed something didn't look right with the cell. There were these red wires, running out of line with the electrode wires. Also, the cell has several holes in it. So it's basically for show.

I measured the cell as putting out less than 1mA short circuit, and about 2.2V open circuit, so it's pretty dead.

Now I'm not that bothered, after all it was only 99p but it really seems shady (puntended) to me to sell these as solar powered!

 

Haven't you seen cheap solar/battery calculators that have a photo of a solar cell instead of a real one?

 

Oh well, no great loss, I've bought a few "solar powered" calculators with fake cells.
These ones are real:
http://forum.allaboutcircuits.com/showthread.php?t=44754
and also if you have a "Poundland" near you they have one with a carabiner clip which is pretty similar inside, but has 2 LEDs and a resistor.

 

You have several latent prints on the solar cell forgery. I would present this to Scotland Yard so they round up the usual suspects and put an end to this tragic consumer abuse.

 

But wait, how does the solar cell come into it?

Well, it doesn't... or at least, nothing is connected to the panel.

Free market in action..... somebody came up with a way to make money off reject solar panels that don't work.

 

Free market in action..... somebody came up with a way to make money off reject solar panels that don't work.

The panel is a QFSOLAR panel. Shenzen China solar technology. Must be rejects; I wonder what they paid for them? Would make interesting silicon wafers, perhaps for experimentation with fabricating my own transistors.

The panel is 3722-9L; the same as in Mark's torches.

 

Hey guys, if we add a good solar cell, can't we turn it into an above unity flashlight?

 

Hey guys, if we add a good solar cell, can't we turn it into an above unity flashlight?

Unless the solar cell is huge and expensive, it is a dim, cheap solar garden light.

 

Unless the solar cell is huge and expensive, it is a dim, cheap solar garden light.

As the proud owner of many solar powered garden lights I can attest to the fact that while they are all dim they are rarely cheap.



(Fortunately I discovered a food store dumping their summer merchandise with a rather large supply of solar garden lights on 75% discount. I got 12 lights for under a buck a piece.)

 

As the proud owner of many solar powered garden lights I can attest to the fact that while they are all dim they are rarely cheap.

Ten of my Solar Garden Lights were very cheap, they were free!
My electrical utility company gave them away and I should have taken many more because there were thousands of them there.

 

You could swap out the battery and the panel with one that is made to be recharged, and a solar panel that works. A solar charging circuit is incredibly simple, and shouldn't be hard to fit in. The flashlight will still be garbage, but at least it'll do what it's supposed to

 

I wonder if these are the same folks that sold DVD rewinders.