Robert Bruninga via EV wrote:
There is no way you can wire 14 solar panels (10' by 20') array in parallel with the "same wire sizes and lengths" (and loss) compared to series. Physically impossible.
Bob, "impossible" is not a useful word here. I'm not trying to argue or "win". I just want to point out that the real world is not as black-and-white as you describe it.
It's obviously possible to wire them either in series or parallel. Which turns out better will depend on the circumstances. For example, suppose these 14 panels are each 10' long and 16" wide (like rolls of solar roofing), and have their + and - terminals at opposite ends. Then it's trivially easy to wire all 14 in parallel with wires along the top, and wires along the bottom. The array is 20' wide, so you wind up with something like 40' of wire.
But if you connect them in series, you need a 10' long wire from the top of one to the bottom of the next one. That's 14 x 10' = 140 feet of wire right there -- far more than the parallel case.
You might say, "But the + and - terminals are normally on the same end." That's true. But I happen to *have* a roll of Unisolar "solar roofing", 18' long and 16" wide. It has both + and - terminals at the same end. But guess what? It has an 18' long wire inside, that runs all the way from one end back to the other. You're getting your long inefficient wires whether you like it or not!
Same is true for a dozen 12v car batteries. Impossible to wire them in parallel with the same lengths and wire sizes (and loss) as series, so your argunment is academically true, but obfuscates the real world.
Didn't you used to have a ComutaCar? It has eight 6v batteries; half in front, and half in back. It has a contactor controller that wired these batteries in series or parallel, for 24v or 48v. The motor was in the center, near the controller, and between the seats.
Look at the wiring. It was all wired with #4 (I think), which you seem to think would have had too much resistance. But it worked. Each battery had its own wires. In the 24v step, the motor might have been running at 24v 100a, but each battery and its wiring only saw 50a. Compared to the 48v step, the 24v wiring loop's length was halved (to halve the resistance), and then there were two such loops in parallel (halving the resistance again). Each wire only carried half of the motor current. So the wire losses were the same in either the 24v or 48v steps.
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