Testing Solar Panels

[OperaHouse]

I got inspired when I saw Will Prouse testing solar panels with a charge controller and some big nearly discharged batteries. He compared it with these $50 hand held panel testers. I thought this was all a bit of hokum. Clearly we can do better than this. I have a number of panels that went thru a lightning strike and several bypass diodes were damaged. Just playing around at this point and really want to get into testing arrays. My array is 60V with 6 parallel strings due to intense shading. The charge controller gets lost on lower localized power peaks going down to 17V at times. Disconnecting the array resets it back to normal.  I've never seen any articles showing these multiple power peaks.  That is what I will be working towards.  Just as a proof of concept, here is the data from an old 12V 100W panel.  Overcast skies and connected with a 50 foot light duty extension cord adding a little resistance, only producing 32W.  Graph is just like in the movies.


Blue is current, flat top is Isc.  Yellow is voltage. And red is the product of the two. power. Current is measured with a 0.5 ohm resistor.

[SparWeb]

Maybe I'm dumb but can you help me with the traces you're plotting?  If I were to guess:
Blue is current?  The key for trace 2 on the bottom says 1.0V so is that scaled to a shunt?
Does the current jump when you short the leads?
Yellow is a slow ramp-up of voltage as the shadow covers the panel? 

The red trace seems to be the multiple of the yellow and blue traces.

[OperaHouse]

That was stated just below the graph. It is amazingly simple to do and can't see why it hasn't been seen before. Just a resistor and capacitor in series. I used a 6,000uf capacitor bank just because it was ready made. A 100uf would probably work as well. Even a $60 Hantek 6022 USB scope has a math multiply function.