The buck converter may be responsible for some of what I see in PWM but not all of it. I know that because the Isc straight from the panel is higher than my 10a meters can take.
On a good note. I put one of the 250w out in pretty heavy overcast clouds. With no shadows at all I saw over 4a. With the sun just definable as a hazy circle I was seeing over 6a. It doesn't sound like much but with three panels that is 12-over 18a. That's enough to keep the trailer functions going including the furnace. I'll add a panel in series to see if the higher voltage does better.
