Large Panel 300 W Slight Shading or Smaller Panel 190-ish-W no shading

I have approximately 1600W of PV panels on the top of my RV, I have eliminated most of the shading issues that come with RV's and panels but I still have a large centrally mounted air conditioning unit, that will be staying on the roof. If you look back through my post history I have posted photos of the RV. I had some roof vent covers causing shading but have since swapped them out for low profile covers and eliminated those issues. 

So the AC unit shaded about 4 or 5 cells in my 275W panels that are 39" wide. If I could find some 30ish inch wide panels quite a bit of that would go away. 

Would going with smaller panels, be a better bet ? I can get pretty close on matching output VOC etc, these are running down into a Midnite Solar Classic 150 MPPT controller. ... thoughts ? 



  • westbranchwestbranch Solar Expert Posts: 5,136 ✭✭✭✭
    You meed ti investigate the amount of loss on  SPECIFIC Panel... and the orientation  of the  PV CELLS on the panels (lengthwise or across) is important as how the shadow crosses the panel.  BB (Bill) will be better able to describe than I  can

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  • OldManOldMan Registered Users Posts: 128 ✭✭✭
    edited January 8 #3
    Always take the higher-power panel if you can afford them. There are always ways to use the power generated when the batteries are full. It's called "run the AC, run the microwave, run the fridge." If you're sporting 1KW of panels and lithium batteries, you are SET unless you run incandescent lights all the time.
  • BB.BB. Super Moderators, Administrators Posts: 29,010 admin
    If you match Vmp-per-string, you connect them in parallel to the same MPPT controller.  Just match high to low Vmp of each string within 10%...  35 to 38.5 volts Vmp for example.

    Sounds like you have addressed the shading problem with low profile vents.

    That is the way to do it.


    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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