Solar Illuminace vs Panel Output

CA Traveler wrote:
How does solar illuminace effect panel output? From yesterdays observation at noonish:

750W, poly, flat, 100F ambient, Vmp=91.7V, Imp=8.18

Logged Varray=75V, Iarray=8.5A, Controller out=605W

Loads were greater than panel output so the controller was in max MPPT state. So it appears that the illuminace is keeping the voltage down but not restricting the amps???

BTW It was very hot all day so at 100F ambient those black panels had to rather hot. So why is the amp output greater than Imp? This raises a red flag for me about the discussions of significant reduction in amps when the panels are hot and PWM is better than MPPT? Wonder what my amps would have been at Jim's 11,000' playground?

No I'm not in denial about reduced amps at higher temperatures. But now wondering about all of the generalized comments about how much better PWM is vs MPPT when the panels are hot. Now wondering if this might be less general and apply to certain panels and/or controllers? There is nothing like having logged controller data to raise red flags.

You have to separate the components of voltage and amps with panel heating. Voltage goes down with more heat but amps go up a bit. Power goes down because the voltage goes down more than the amps go up, and also because there are more volts than amps in the watts.

What you get with a hot panel is reduced input power to the MPPT controller (which has a buck converter in it) which is then reduced further by the controller(which might also be getting warm at 100F (wow!)), leaving whatever output power to go to the batteries. Divide that output power by battery voltage and that's your charging amps at the moment.

Meanwhile the PWM controller takes the panel amps and passes them to the battery and doesn't care about the power being less in the heat as long as there is enough voltage overhead to charge the battery.

So you could get to a point where the output amps from the MPPT is the same or even less than what you would get with straight PWM from the same rated wattage of panels. But then you also run into the overhead issue when doing PWM 24-24 with 60 cell instead of 72 cell panels.

I was only able to compare 24-12 MPPT vs 24-24 MPPT with a 60 cell panel and that vs 24-24 PWM. So I did not get to compare 24-12 MPPT vs PWM with 72 cell panel vs 36 cell panel.

I posted results of testing all that a few times lately, if you search. I got less with 24-12 MPPT and the same but more with 24-24 MPPT and PWM with a hot panel (but not as hot as the OP's must have been)