Increase Output Voltage of Solar Cells

[Joe F]

I am helping my son do a project. We would like to know how to increase the output voltage. For example we have three 6 volt 50ma cells and would like to make 18 volts

 

[Bobbywhy]

Connect them in series, just the same as you would connect "D" cell batteries in a multi-cell flashlight. Negative lead to positive lead, and so on. You end up with one + lead and one - lead left over. Your three six volt cells connected in series will give you approx. eighteen volts (open circuit, no load).

 

[Joe F]

I tried that but we still had 6 volts. Am I not seeing something? or it is the quality of the cells? Also I am a electrician, we have a simple formula for voltage conversion we use in the field. Example, we use 100 amps at 480 volts thru a transformer to get 200 amps @ 208 volts. is there a simple formula for dc to ac that is as simple without going into harmonics and wave distortion. Say if we have 1000 volts dc what can we expect to get in ac volts
Thank you
Joe

 

[Bobbywhy]

Joe F, first of all, your solar cells are Direct Current devices. No need to try to mix transformer formulas that manipulate Alternating Current because they are two different kinds of electricity. AC transformer laws do not transfer over to DC circuits.

Actually one single solar cell only generates about one half of one volt. My mistake was to not notice that detail in your first post. What you have is three “arrays” or “modules” of cells. Inside each module are probably twelve solar cells connected in series to give an output of six volts.

Now that our terminology is clear, I’ll try to troubleshoot your problem from here. You said you connected them in series and still got six volts. This sounds wrong; they should add up. I would separate those modules and measure each one individually to verify each was giving six volts at no load, or “open circuit”. Use “one full sun” to illuminate the module. If each module is indeed measuring six volts you should be able to add them in series, just as I described earlier, to get about eighteen volts.

Lots of good information on solar cells to read and study at the two sites below:
http://www.solarbotics.net/starting/200202_solar_cells/200202_solar_cell_use.html
http://en.wikipedia.org/wiki/Solar_cell

If you get no joy, come right back here and let us know!

 

[NascentOxygen]

I tried that but we still had 6 volts. Am I not seeing something?

It sounds like you may not have had all the polarities lined up! Just like batteries, you have to be sure of connecting the + wire from one panel to the – wire of the next.

If you get just one of your 3 panels around the wrong way, its 6V will cancel the 6V from one of the others, leaving you with just the 6V from the third one! Your multimeter will identify the + and – wires from each individual panel and allow you to get them all correctly connected.