# .5v to 5v up-step

Discussion in 'The Projects Forum' started by dprice, Mar 11, 2012.

1. ### dprice Thread Starter New Member

Mar 11, 2012
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I was looking to build a solar usb charger for all of our junk while we're out n about... Shopping about I found auctions for 3*6 panels, I figured a decent buy for about \$1 each...

Average Power (Watts): 1.8 Wp
Average Current (Amps): 3.6 Imax
Average Voltage (Volts): 0.5 Vmax

The average power seems to be about .3 in the sunlight, if I can get something that'd take down to .2 it'd be ideal since I work in an office. They have decent efficiency, but for smaller projects, like the one I'm thinking, I need to step up the voltage, and can sacrifice the amps for it...

2. ### thatoneguy Expert

Feb 19, 2009
6,349
732
To go up 10x in voltage, you would go down more than 10x in current.

You'd be far better off buying more cells to put in a series/parallel array to get the voltage you need at the required current.

Solar electric efficiency is poor, around 20%, much less in an office environment, so a boost switching supply would take another 10% of the power away in the step up process, making solar arrays the preferred method. Most panels are already arrays to meet either current or voltage design parameters for what the panel was designed for. It's just a matter of rearranging how they are connected, and maybe adding 10x as many.

3. ### dprice Thread Starter New Member

Mar 11, 2012
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Well, I can lose the amps to step up, since usb is only 1a. Even parallel with two panels wouldn't be too bad, 1v and an average of maybe, .5 or .6...

4. ### DickCappels Moderator

Aug 21, 2008
5,741
1,797
Switching a couple of amps at half a volt is very difficult. You tend to loose a lot of power in saturation of the trasnsitor/FET and the IR losses in the inductor/transformer.

The circuit below illustrates a concept that might work if you can get a little more voltage out of your panel. You might be able to get it to start at 0.5V if you use a germanium transistor for the bipolar transistor. Note: The circuit is only a proof of concept, not a finished circuit.

5. ### dprice Thread Starter New Member

Mar 11, 2012
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Suppose I'm pretty thoroughly confused by all that...

6. ### dprice Thread Starter New Member

Mar 11, 2012
8
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when I grabbed them I thought it might be as simple as an op-amp or something.

7. ### wayneh Expert

Sep 9, 2010
16,102
6,219
Op-amps are good at operating on information moreso than power. They are powered devices and output no more than they are supplied. That is, nothing practical passes from the input side to the output.

8. ### magudaman Member

Feb 27, 2012
31
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This device is pretty awesome little switcher,might be what you need and is \$20 bucks.

.5V min input 5v output

http://www.dimensionengineering.com/lvboost.htm

9. ### wayneh Expert

Sep 9, 2010
16,102
6,219
I've seen several "energy harvesting" devices but at \$20, they're not so interesting for most hobbyist applications.

10. ### russpatterson Senior Member

Feb 1, 2010
353
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Another option is to get those .5V cells and cut them into smaller horizontal strips and then solder them together in series to get your voltage stepped up. The thickness of the cells you buy will dictate how easy they are to work with. Thicker is better (and slightly more expensive). Google glass cutting for ideas to make clean cuts. Also there's plenty of youtube videos out there on how to 'tab solar cells'.

11. ### dprice Thread Starter New Member

Mar 11, 2012
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I actually had that thought cross my mind throughout the week... Cutting them would be a pain since they are pretty brittle, I wonder if scoring them with a decent razor knife would be the ticket.

12. ### dprice Thread Starter New Member

Mar 11, 2012
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That looked pretty promising (besides the price tag) but, the max current on that little guy is 1.5 amps.... Do you think that'd mess it up? I wonder if I can find something similar in a lower price range.