red31 wrote:
If there was zero voltage loss wouldn't the panel be at 14.8 and not at 15.3 so there would be no loss? ie, in both cases you'd read the iv or power curve at the same spot?
For PWM essentially yes. It's not the same spot but there is a very small drop in I as you move from true Isc (current at 0 volts) until you get close to Impp, and that is almost the same spot on the vertical axis. So at 14.8v on most panels you'd get a tiny bit more current than at 15.3. But they are essentially both Isc.
But there is overall loss of power from the panel by running it at Isc instead of Impp, because power = current * volts, and the volts at mpp are generally much higher than the battery voltage, with only a minor current loss.
Picking Vmpp in real time to actually maximize power generated, and getting it converted efficiently to a voltage the battery will accept are generally the trick and where the real world losses start to take their toll.
Jim
