Quote:
Originally Posted by Bill
Wayne -
Couple things.
First, since they are nearly black and designed to be very absorptive, the panels get quite hot in direct sunlight. They depend on having some clear air space on the back side of the panel for cooling. If you mash them up against the trailer roof, you cut off the air circulation. This risks damaging the panel, and doesn't do a whole lot of good for the roof. In addition, their ability to generate charge drops with increasing temperature.
Second, the blocking diode does not require 1/2 amp of current to overcome the "gate" - I'm not sure what that term means, as there is no "gate". I think you are referring to the fact that a diode drops about 1/2 volt of voltage as it conducts current. Since the panels generate more than 17 volts, and you need less than 15 volts at the battery or the input of the charge controller, the 1/2 volt drop doesn't cost you anything.
I suppose you could argue that the 1/2 volt would mean something if you were using an MPPT charge controller - but I don't think anyone would spring for an expensive MPPT controller on a 160-watt array.
I recommend that you follow Dave / Shrimp Burrito's suggestion, and read the threads (I think there were several) in which Rocky Mtn Ray described his reasoning, his experiences, and his results. He laid out his thinking over the course of a year, I think, and I have never seen a better description or guide - even on the solar power newsgroups and forums.
Bill
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You're right....I meant 1/2V not amp duhhhh!!!. However, it is a net loss over the charging cycle. When I was on my yacht, I used a diode when I left the boat for long periods (those panel did not have a built-in diode). I had a pretty expensive digital battery analyzer on the boat. The difference was provable when having the diode hooked-up during the day while charging. I used to have notes in my log on all this stuff but I've long since lost my ship's log. It's a mute point because most panels now have built-in diodes.
I also considered the heat issue with the panels. I can drill 3/4" holes all around the perimeter of the frame to help with air circulation and heat removal. However, I am leaning toward storing the panels inside the camper and putting them on the roof (on risers) before we lift the rear (lower) roof. It's just another step during set-up. I have spent a lot of time ad energy eliminating "steps", I'm not exited about adding a step.