I have a 75/15 MPPT controller with two Renogy 100w panels. I noticed a performance drop and cannot figure out what is going on. Everything seems fine until I connect to the controller. Then I experience a voltage drop from ~21v to 16 to 17v. My panels are in parallel and I'm seeing half the amperage I usually see.
I isolated each panel and one of the panels is not liked by the controller for some reason. Testing this panel I see 21 Volts, and when I short POS to Neg I read 4.5 to 5 amps on the panel. But when I connect it to the controller it tanks for some reason. I wired my panels in series and I read 42 volts but when connecting to the controller it is only 23 volts.
What could be going on? It makes no sense to me. Should I replace the panel?
Does this have to do with the 36 minimum cell requirement I hear about and one cell is bad? These are flexible panels and one cell does have a small opaque area in the middle of the cell closest to the negative output.
I have seen others having similar issues. When I connected the panel solo to the controller it only shows 14.? Volts and my lithium charge profile is set to 14.40.
Please advise as to what the problem could be. I pretty much ruled out any bad connections and the other panel by itself seems to be performing as expected.
