Walt,Regarding the current limit power supply to simulate a solar panel (which I think is clever), MS can correct me if wrong but the power supply was first setup with a voltage at 17.4 and then the current limit was adjusted to be .4 amps. This means that the supply will put out 17.4 volts as long as the load current is below .4 amps. If the load increases past the .4 amp point, the power supply voltage will begin to drop in order to limit the current.
If you look at the video in the first post, at about 2.36 minutes in, you can see the mppt controller search algorithm in action and it actually looks like it works nicely. When the switch is flipped connecting the current limited power supply to the controller solar input, the current first starts at zero but then quickly ramps up. If you look to the left side of the supply, you can see the current limit display light come on but the controller is still able to cause an overshoot in the current just for a fraction of a second before the power supply stabilized at .4 amps - and the current limit light stays on. The controller did a nice job as it put the power supply in current limit but just barely as it allowed the maximum voltage the supply was set at. The controller did find the maximum power output from the supply, found it quickly and seemed to hold it stable. I can’t see anything wrong with this setup..
I pulled this from the Genasun web site
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The MPPT benefit is:
10% additional power in the summer. (Hot panels have a Vmp closer to battery Voltage.)
30% additional power in the winter (Cold panels have a higher Vmp.)
50% in partial shading (Partial shade causes a dramatic increase in Vmp. We have consistently seen 50-60% increase in energy harvest from partially shaded panels.)
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What I wanted to point out is the 10% additional power in the summer from the manufactures web site and this is what we are likely to see for a sailboat application (not the great numbers from this experiment). If you’re using a panel when it’s warm and sunny out, the panel is maybe 15% efficient for electricity but they are much more efficient for collecting heat (nice dark color). Sometime just feel how hot a panel gets. The maximum power point is temperature dependent and drops with temp - mostly due to voltage drop.
The 50% increase in partial shading condition is interesting however.. but I wonder if this occurs when the power output is very low to begin with and 50% increase of a low number is still a low number??
It was actually set to 4.0A not 0.4A. That said this is a "best case" scenario. As you stated solar panels have worse performance when hot and better when cold. In the "real world" I see average performance increases of 7-15% with MPPT not the 20-30% often bantered around.....
I only used the power supply because it is consistent and I can set it to maintain its consistent output where a solar panel in an A/B is dependent upon the sun and sky which change, especially here in Maine.. I used the power supply for a cleaner "apples to apples"....