it’s a “100W 12V” panel… but that is or is not 100W when running at 12V (and thus 8.33A)?
The specs seem to say max power 100W is at Vmp of 20.7V and Imp of 4.84A (20.7V x 4.84A = 100.2W).
So if it’s actually running in full sun, optimal alignment (at STC, etc) then it’ll be doing 20.7V?
And if it was not full sun and chugging along at 12V then what’s the current? Still 4.84A (thus making 58W) or is it some smaller amount of amps, and if so, how many?
My point here is what V and A do I do my array sizing math with?
It also includes variation from STC (standard test conditions @ 25c) solar radiation (insolation).
Insolation varies with cloud thickness, and/or panel to sun angle.
Panel current varies with insolation %.
Panel voltage varies with panel temp.
The power calculation would be.
( Imp x insolation % ) x ( Vmp @ panel temp )
Easy.
Dont forget the panel Vmp has to be a minimum of 5v above the battery voltage.
I’m planning to run a hybrid array — 2 arrays wired to the controller in parallel, each array being made up of 2 panels in series. I figure that gets be 40V at 10A at the controller.
But that depends on my initial question about doing the math…
As you can see from the graph above, as the light level falls, Vmp reduces very slightly, the main change is in Imp. For a first order approximation, assume Vmp is constant and Imp is proportional to the radiance. So for your panel it will always produce around 20V but if the light is half as powerful then the current will be around 2.4A so power = 48W.
