When you examine the terminal you will more than likely find signs of oxidation.
Burn marks on solar panels.
Just like a car battery solar panel system battery terminals can burn out.
When you use a charge controller that is what it is doing anytime the battery bank is full tapering off the.
This is a sign of a burnt terminal.
A burnt terminal can be cause by wiring too many panels to one terminal.
Mark having solar panels in the sun without a load on them should not damage them.
About half of the panels appear to have burn marks of an unknown origin.
Badly soldered connections cause low resistance in the part of the panel that receives the power generated by the cell.
If you work in the solar panel installation business long enough you ll inevitably come across solar panels with strange brown spots.
This is because a pv solar panel is made up of a string of individual solar cells connected in series with one another.
Hotspots on panels are mainly caused by badly soldered connections or are a result of a structural defect in the solar cells.
These have been seen on panels manufactured by smaller suppliers and large distributors alike.
If even a small section of a photovoltaic panel is shaded for example by the branch of a tree there is a very significant drop in power output from the panel.
Typically they are in the same exact place on multiple solar panels.