Solar Panel Knowledge

This past week I learned some valuable knowledge about solar panels that I would like to pass on. I own a 2011 CI 560 Ultra which has solar and a Domestic refrigerator. I am on my 3rd AGM battery and I was concerned that my 8 year old 100 w solar panel may have degraded. I purchased an inline watt meter off of amazon ($15) to do some testing. Note I have a degree in electrical engineering but this was not a big deal. When I got the meter I put some MC4 connectors on and put it inline between and panel and the CI and stated testing. I had the Dometic plug into the 12v so I had a load because the battery was charged. My panel was in partial shade (about half) and I saw no wattage coming from the panel. I moved the panel in full sun and got a reading of 65 watts (the sun was low). This made me wonder what effect shade had on a solar panel so I took my hand and shaded just one cell (one square on the panel) and to my amazement the watts dropped to 30 watts. I then took a piece of cardboard and slowly moved it over the panel and saw the watts drop to zero when only one row of cells were shaded. I then got on line and googled “effects of shade on solar panels” and the articles I found confirmed what I observed. One cell shaded will cut the power of a solar panel in half or more. One row of cells or more will cut the power to zero. The cells are wired in series and the circuit is designed to do this to protect the panel. I will list the other things I learned below.

1. A solar panel wattage rating does not mean it will produced that wattage. My old and new 100 watt panels have only produced a maximum of 75 watts each. I live in Arizona and tested the panels in 100 degree heat. The wattage of a solar panel decreases when hot.
2. My 100 watt solar panel was dirty and dusty when I stated the test and was reading 30 watts. When I cleaned it the wattage increased to 70 watts. You must keep your panel clean.
3. As stated above shade will kill the wattage to zero. I have not tested my panels on a cloudy day but I would guess the wattage drops significantly or maybe even to zero.

I just watch some Youtube videos on this today and they confirm what I have observed.

KEEP YOUR SOLAR PANELS IN FULL SUN (NO SHADE) WHEN CHARGING

 

ALL true, thanks for sharing. I'm learning as I go as well. Lots of great info out there and on this forum.