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Say I have one 4W PV cell and one 2W PV cell (both producing about .5V). I know enough to say that maximum current of the first cell is 8A (4 / .5) and the maximum current of the second cell is 4A (2 / .5).

In series, what is the maximum current of these cells together in a solar panel?

Is it 12 (the total)? Or is it 4 (the limit of the smaller one)?

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  • \$\begingroup\$ It is the limit of the smaller one. But probably your 0.5V is open circuit voltage. When delivering full power, the voltage will be closer to 0.33. See my comment in Camil Staps' answer, too. \$\endgroup\$
    – Bobbi Bennett
    Apr 28, 2013 at 15:41

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When connected in series, the maximum current is as high as that of the weakest link, so yes, 4A. The voltage will be the sum of all cells, so 1V.

When connected in parallel, the maximum current is the sum of all cells, 12A in this case. If you do this, you should only connect cells of the same voltage in parallel, otherwise you get unwanted current flows.

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  • \$\begingroup\$ Not quite.. They are closer to constant current, not constant voltage like a battery. It is when they are mis-matched and in series that there can be trouble; the weaker cell can reverse bias, and start to dissipate the power of the other cells. \$\endgroup\$
    – Bobbi Bennett
    Apr 28, 2013 at 15:37
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    \$\begingroup\$ @BobbiBennett: I think you are confusing series vs. parallel connection. \$\endgroup\$
    – Dave Tweed
    Apr 28, 2013 at 15:54
  • \$\begingroup\$ @DaveTweed, nope, I'm not. Look up 'shaded solar cell bypass diode'. \$\endgroup\$
    – Bobbi Bennett
    Apr 28, 2013 at 16:05
  • \$\begingroup\$ @BobbiBennett: Shaded cell bypass has nothing to do with reverse-biasing a cell; it simply reflects that a shaded cell will pass very little current, and since the current of a series array is limited to the smallest current value of any cell, it severely limits the power available from the array. It is in a parallel connection that a stronger cell can force current through a weaker cell, wasting power, and a blocking diode can prevent that. \$\endgroup\$
    – Dave Tweed
    Apr 28, 2013 at 16:12
  • \$\begingroup\$ pvcdrom.pveducation.org/MODULE/HotSpot.htm \$\endgroup\$
    – Bobbi Bennett
    Apr 28, 2013 at 16:22

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