Solar Panel Voc-MPPT?

BFL13 wrote:
Wondering if there is any relationship between measured Voc and MPPT performance with a 24v panel.

My 12v panel has a Voc rating of 21.9 and Isc of 8.2, but I often see 8.2ish when Voc is only 20.3ish. That's fine, I just want that Isc. ( I know they have different coefficients from 25C)

But now with MPPT and a 24v panel I am seeing the same sort of thing.
Panel is rated Voc 37v and Isc 8.3a In the sun trying it out I got 34.5 Voc (varies -did see 36 at one point) and Isc of 8.24a

Normally, I would be happy at seeing that Isc, but now I am wondering if that 34.5 Voc instead of 37 rated would show up as lower amps to the battery via the MPPT.

(Vmp is 30v and Imp is 7.7a)

Is it still the case with MPPT that if you are seeing the Isc at the panel, all is well, or with MPPT does Voc matter now, or what?

Thanks.

I wish I had measured the VOC while camping up there to put what else I saw in perspective.

Yes VOC has a impact on MPPT since the controller is converting excess volts to amps. I can't explain it all techy like but going from a mile high to 10,000 ft can show it.

I see a big jump in PWM (ISC) up there from 9a to 14a. In the early morning I see double the MPPT amps that I would see in Denver. The smallest increase is in max MPPT is amps at mid day when I expected the most. There I saw less than a 2a boost over the max in Denver.

What I believe is happening is at some point I hit the max VOC of the panel and in Denver I was close to it already. The boost in the morning is because the voltage came up faster than in Denver and that's when I need the power anyways. I have no idea why I'm seeing such a jump in PWM and I'm not complaining.

I doubt that even at 10.000 ft I'll ever see the rated VOC for either of my panels.