mike-s wrote:
ktmrfs wrote:
I've got in theory 60A total charging current. Now that's in theory, and today with the roof panels flat and being near 45 degrees latitude the sun angle limits the roof panels to around 20A total.
Today, at solar noon in Portland (when you would get peak charging current), the solar altitude was about 62 degrees. That's 28 degrees off normal (perpendicular, AKA zenith angle) for a horizontal panel. cos(28)~=.88, so the panel would receive about 88% as much light as it would if positioned normal to the sun. It's a bit less than that due to thicker atmosphere at lower angles, but not much unless the sun is much closer to the horizon. To get only 1/3 the output is due to factors other than the sun angle. The sun would have to be closer to 20 degrees altitude (that's like 8-9AM) to produce that output based on sun angle (or clouds, haze, shadows, etc.).
my 60A was the total of portable AND roof panels, 30A each. the 3 roof panels were giving me around 20A while the 3 portables with even approx aiming would have maxed out the 30A portable controller. And I measured it around 11-AM PDT, which was about 10AM real time which puts the sun at a pretty low angle. I'd have estimated the sun angle to be around 45 degrees which would give me about 25A in theory. so I was pretty close to what I would have expected out of the roof panels. and at that time the solar angle was off in two directions relative to the panel, my panels would have needed to be tilted up and rotated counterclockwise to be perpendicular to the sun which further reduces the efficiency.
so around 1pm I suspect the output would have been noticeably higher, but by then the batteries were no longer in bulk mode charging but absorption and the charging current dropped below the panel output as expected.
