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Using a single Solar cell and changing it's power specifications with a booster? Answered

I have solar cells that are over 6Amps but only produce 0.5 volts. Would it be possible to use a series of resisters or boosters to change the output to a higher voltage and a significantly lower current?

I'm aiming for something along the lines of 4volts and under 1000 mAh?

Any thoughts would be highly appreciated. 

Thanks in advance! 


The usual trick with solar cells (and also with battery cells) is to stack them in series to get more voltage. This is a trick that works well, and I think it work well for your thing, if you can find around 10 cells, each with about 1/10 the area of the cells you presently have.

Oh right! But you want to work with the parts you've already got. And cutting apart the cells you have without turning them into useless shards,


may be very tricky, if not impossible.

I suppose it is possible to build a DC-to-DC converter, but this adds complexity, and inefficiency (in the power lost in powering the converter). Also I think it might be tricky finding a DC-to-DC converter that will take less than 0.5 V as its input voltage. I mean that voltage is less than one diode-drop, for silicon, which is about 0.6V.

I mean even the humble Joule Thief


...erm wait. That caption blurb says Joule Thief can run from 0.35 V?!

And that is a little mysterious to me, since the base-emitter junction of Joule Theif's NPN transistor needs like 0.6 V to get turned on.

I dunno? maybe you could try the Joule Thief? Or something like it. It is possible to find an inexpensive boost converter inside of a single cell white-LED flashlight. Actually I have hacked apart such a flashlight, and took pictures of it, here,


but I have not examined what is the absolute minimum input voltage needed to make this circuit work.

Finally, I thought I would mention that the people who sell solar cells like to quote the biggest, most impressive looking numbers. Actually this is true of people who sell anything, but in the case of solar cells (or even mulit-cell photovoltaic modules), the numbers they are quoting are usually open circuit voltage, Voc, (voltage at zero current) and short circuit current, Isc, (current at zero voltage), both measured in blistering full sunlight.


However, because those are two points on different ends of the current-voltage characteristic, you cannot just multiply those two numbers together and call that an estimate of the maximum power the cell or module can produce. The actual voltage and current at which a solar cell produces its maximum power, or even any greater-than-zero amount of power, is a point somewhere in the middle of its I-V characteristic, at voltage V< Vos, and current I < Isc.

Thanks for the detailed information! I've thought about using two or three of my current cels to get at least 1 to 1.5 volts with the same 6Amp current rating. I'm not opposed to do that if a single cell can not be converted with a DC to DC converter.

I've also thought about cutting my current 120mm by 120mm cell into three and wiring them in series, essentially turning the same surface area into the 1.5volts that i would need to go the DC to DC route. I've only recently been made aware of using solettes. My cells look like they could be cut with a sharp pair of scissors. there is no protective layer on them just yet. Would it be crazy if i used a box cutter or a glass cutter to slice them into bits?

Thanks again!

I think it would indeed be crazy to try and slice and dice your pretty new solar cells.

Of course I don't know exactly what kind of cell you've got. There are a few different kinds out there.

I remember one time I bough some kind of thin-film cell that was printed on a thin piece of metal, and I thought it would possible to just cut one into smaller area cells, but after I made the cut with my metal cutting shears, the cells (or rather pieces of cells) did not work anymore.

The old style cells made from crystalline silicon seem to break into pieces that still function individually as a smaller solar cells, but these are difficult to cut precisely because they kind of break in unpredictable directions, the same way glass does. I have some pictures of that kind of cell here,


and what I was trying to do there was just get a single, small, approximately 1 cm^2 in area, cell I could use as a small light sensor.

In summary, I do not recommend slicing and dicing.

Regarding DC-to-DC convertors that can run from very small input voltages, I noticed some links in the Wikipedia article on Joule Thief, that mentioned some other DC-to-DC convertor made to run from very low voltage, like 0.1V! So such things exist, and if USP4734658


and the related art, makes sense to you, then maybe you can build your own very low voltage input DC-to-DC converter.

Linear Technology have some VERY low starting voltage stuff, like 0.02V

Whu... what? Like 20 mV? I mean depending on what the thing is, there could be real power there, assuming sufficient current is available. Wow! I'm going to have to look into those ICs. One of those might be just the thing for the single thermocouple power plant I always wanted to build.

There are some gotchas, they're really energy harvesters that boost up the low grade incoming onto a supercap, and they need a wound component - the topology is breathtakingly clever, as you expect from LT.

Connect the cells in series.

Thanks so much for the quick reply! I know if i use the cells together i can boost the voltage naturally by connecting in series but i'm limited with space so my plan is to just use one cell and change it's 0.5 volt output to about 4 volts allowing the current to significantly drop due to a rise in voltage. Basically I's like to match the voltage of a 3.7 volt battery so i can charge it off a single sollar cel...

You'll need pretty special converter to do that, and one you may have to make yourself, using some fairly exotic silicon.The LTC3105 will push 400mA from a 0.5 V panel into a Lion cell.

If you wire the cells together correctly you won't need to use a DC to DC converter to get the voltage you require. If the current is too much for your batteries to handle then you can use a current limiting circuot but then your loosing a lot of your power to heat.