Unexpected voltage drops in panel array

[timblack1]

As I mentioned at

https://www.facebook.com/timblack11/posts/pfbid02D6p7bH7TykdZEWu6wKcU87V7dUyV1VvmmaLrkD4wZTsNpQzX8KCE5p6ZJybETywEl

,

Our panels are in a 7 series 3 parallel array, labeled 1-7 and A-C, respectively. We tried shading various panels in the array to see how it affected the whole array’s open circuit voltage, so we can discover if a total-cross-tied configuration produces more power under the same shading conditions. We hypothesize it will. In the process, we noticed two unexpected voltage drops in the results. The first voltage drop is between panels 4A-4B and 6A-6B. The second is between panels 1A-1C and 4A-4C. The voltage drops must not be in column A because we saw no differences in the voltage drops when we shaded individual panels in column A alone.

What do you think could cause these voltage drops? While assembling the array we noticed one corroded MC-4 connector and replaced it. Perhaps there is another corroded connector, a panel with extra internal resistance, or a dirty panel. The voltage drop is small but still might be worth investigating.

Here is how we are narrowing down the location of the voltage drops. https://www.facebook.com/photo/?fbid=10160460204840847&set=pcb.10160460235695847

 

[MaikaiLife]

I think you already have the best ideas, corroded connectors, higher internal resistance, or maybe just a panel that wasn't made to the same quality level as the rest of your panels.