I have a quick question about cell wiring

[ddlefty357]

I'm making a solar panel with 95 3x6" cells. Each cell is rated at .5 volts. If each cell was in wired in series that would be a 47.5 volt panel. I want the panel to be about 28.5v (for connecting to 2 12v batteries).

So my question is: can I connect 57 of the cells in series to make the 28.5 volts and then connect the other cells in parallel? Will this damage the cells? Or am I just being an idiot and should make a 57 cell panel?

[Mike90250]

That's exactly how large panels are made, a combo of series and parallel cell wireing.

Make the array several volts higher than your end use, charging a 12V battery needs about 16V, so design for 17-19v puts you in the ballpark all the big dogs use.

[indalecio.feng]

Normally you should connect 72 cells in series for 24V system.

[garybeck]

also, realize there is a difference between operating voltage, oper circuit voltage, and nominal voltage. While the cells might be ".5V" that is more than likely the nominal voltage and its actual voltage could be different, especially if you are getting surplus cells. it is best to use a meter and actually measure the open circuit voltage of each cell first, and then of the string as you add cells. it does not have to be full sun when you do this (crystalline cells will show full open circuit voltage under 50% sun or even less; the amperage is much more directly related to the intensity of the sunlight). Once you know the open circuit voltage, you know your operating voltage will be somewhat less. And your operating voltage still needs to be significantly higher than your nominal battery voltage, which is 12V. So when in doubt make sure you got enough volts, or your won't have any energy flowing, even when the sun is shining. it's better to have a little extra volts than not enough.

[Jason]

welcome ddlefty, thanks for joining.

i'm moving your post to the "Assembly and Connection" forum