I have a 'toy' array in my back yard. I call it a 'toy' because it's really just there for me to mess with... to get a feel for how shade, and other configurations effect it and to compare PWM and MPPT charge controllers. I've got a 10.7kW grid-tie on my roof that provides all the energy I need. The ability to run a few things off the 8 panels in my back yard is just a perk.
I previously had 2 sets of 2 in parallel but recently added 4 panels so I was running 8 60 cell panels in series. They were arranged with 4 in the front and 4 in the rear... mostly in the same orientation.
I happened to notice that the MPP of the 8 panel string was ~120vdc. Which was a bit low since the MPP of each panel should be ~25v. Come to find out that the rear 4 panels were only contributing ~20% of the power. A FLIR image revealed several hot cells and a very hot J-box which was actually slightly deformed. I removed the bypass diodes from one panel and they were all shorted... I'm assuming the other 3 panels are the same. Panel appears to still work so I might just replace the diodes and carry on.
Anyone have any theories? Lightning? Was the orientation off enough that somehow the front four were driving the rear four and over heating the bypass diodes? There is shade. Could the bypass diodes have overheated?
These are 255w Astronergy panels...
FLIR0051.jpg
I previously had 2 sets of 2 in parallel but recently added 4 panels so I was running 8 60 cell panels in series. They were arranged with 4 in the front and 4 in the rear... mostly in the same orientation.
I happened to notice that the MPP of the 8 panel string was ~120vdc. Which was a bit low since the MPP of each panel should be ~25v. Come to find out that the rear 4 panels were only contributing ~20% of the power. A FLIR image revealed several hot cells and a very hot J-box which was actually slightly deformed. I removed the bypass diodes from one panel and they were all shorted... I'm assuming the other 3 panels are the same. Panel appears to still work so I might just replace the diodes and carry on.
Anyone have any theories? Lightning? Was the orientation off enough that somehow the front four were driving the rear four and over heating the bypass diodes? There is shade. Could the bypass diodes have overheated?
These are 255w Astronergy panels...
FLIR0051.jpg
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