Soon-to-be engineer with RE passion.

[Turbo2Tonos]

Hello guys, my name is Davis and I'm from Panama. I'm currently finishing my B Sc. in Electromechanical Engineering at Panama tech, but I want to be an MSc. RE Engineer in the future.

Currently I'm working in a DIY project for a 15x5 solar cells grade "B" panel. This cells output are averaging by manufacturer 1.8W, 0.5V, and 3.6A. Most of them are just slightly scrapped off in the corners, or will have a small spot where there are missing white lines in the negative side.
Now, I already soldered all the tabbing wire for all the 75 cells, and already sold toghether 5 for testing which yielded 3.7 Amps when shorted in sunlight today (no clouds at that moment) but then i have a connection configuration question I hope you guys can help me with:

1. Either I connect all cells in series, getting ~37.5V @ 3.6A or less for the most inneficient,
2. I connect each row in parallel which should yield 7.5V @ 3.6*5A
3. I connect 2 and a half row in parallel with 2 and a half row, giving me 18.75V @ 3.6*2A and one cell in left over.

Right now im thinking about the third option, because it's the recommended voltage to charge a battery and i can get a bit more current output. But then, the first option would be more reliable, because i will be above 12V at almost any weather condition i guess?

What do you guys think?

Thanks!

[Sunking]

1. Either I connect all cells in series, getting ~37.5V @ 3.6A or less for the most inneficient,

I hope they did not teach you that in school. Higher the voltage the greater the efficiency. Why do you think utilities run voltage up to 1 million volts?

[Turbo2Tonos]

I hope they did not teach you that in school. Higher the voltage the greater the efficiency. Why do you think utilities run voltage up to 1 million volts?

Actually I was not speaking about P=I^2*R right there. I was talking about the fact that the current output will be as much as the weakest bond (the cell that had the lowest amperage output) which i called "the most inneficient". I apologize if did not explained myself.

Thanks for your reply. Any suggestions?

[Mike90250]

Wire in series for high voltage, and then pray that your containment does not burn.

I hope you are only doing this as a "science experiment" and not for a household power system. Most DIY panels in humid areas have a very short lifetime, between the faulty cells (visible flaws and ohmmeter measurable flaws are only about 10% of the reasons cells are faulty) and the buildup of corrosive humidity, they are destroyed soon.

[Turbo2Tonos]

Bypass Diode

Now that you mention burn, I was thinking I will set up 4 bypass schottky diodes. The kit i bought came with 2 15SQ045 Diodes (15A, 45V, 0.2mA reverse current @25celcius).

Im no expert but, I think these diodes are way above my requirements. Could you guys help me selecting correct diodes?

Since i will be bypassing every 15 cells, 15x0.5=7.5V, and 3.6Amps rated cells, what diode am I looking for?
10V, 5Amps or something like that?

Thanks for your time!

PS. please take a look at my arrengement.
IMG_20130930_1816332.jpg