Because of shadows from semis, buildings, bridges...etc hitting the PVs, and because of less tree cover. Also because of rapidly changing direction of illumination and most likely little tilt. But especially the very rapidly changing illumination/shadow pattern, and what different controllers might make of it. Many factors. If you look at the solar race cars, they have much more advanced control strategies than most stationary charge controllers.
I imagine PWM would run effectively the same.
But I am curious in what people here actually observe with their set ups.
Jim
