This is an old revision of the document!
patterns in solar harvest
unscientific terms
Rated = the actual panel rating in watts under lab conditions
MPPT theoretical = 82% of rated, allowing for 5% DC-DC losses and 13% temperature derating at 70deg F ambient.
In my case, Rated is 570w and MPPT theoretical is 467w.
observations
Overpaneled configurations (relatively high panel watt to batter Ah ratio) tend have two main features:
improved charging in adverse conditions
apparent low output in normal conditions - this occurs because the batteries are typically in Absorption with battery charging demand dropping by solar noon; there is rarely an opportunity to
demonstrate full output.
Note that overpaneled systems are typically only making
full sun normal
bright sun through thin / cirrus clouds, shadows thrown
bright overcast, sun is completely occluded but too bright to look at comfortably, no open sky, no shadows - 25% of rated, 67% of theoretical
overcast, can look at sun's assumed position - 20% of rated
125w, 22% of rated
100w, 18% of rated
75w, 13% of rated
dark overcast, cannot locate sun - 10% of rated
exceptionally low yield - less than 5% of rated
ununsual scenarios
wildfire smoke -
8.98W at noon, sea level. 1.5% of rated, 1.9% of theoretical during September 2020 wildfires in Oregon.