Dnnap wrote: ↑Fri Jan 22, 2021 5:16 am
My current test location (Detroit/Windsor region) the sun angle from the horizon (panel tilt from vertical) = 29° for January. My panels are approximately 15° from vertical.
The irradiance value for my current location for January with the current panel tilt is approximately 2.22 kWh/m2/day. This should yield much higher energy than my test results are showing. My maximum daily energy harvest with 1890w PV array was 900wh with sun for the full day.
I will recalculate these angles once I move the system to their final destination, which will by much worst since the move is almost 800 miles north.
Ok, just for grins, (and the weather in the PNW is GORGEOUS today,) I dug out a camping panel set I bought last year.
It is sold as a 100w, foldable unit with built in USB charger ports, and a set of the plugs for daisy chaining panels together.
The manual that comes with it says the MPP is around 18 volts or so. Open VOC today at 40 F was 24volts.
I didn't get to start testing until 1345 PST (the BOSS had other plans for a bit,) but still the results are interesting.
I drug out the lawn tractor to use its battery for a test load, and it also worked for a place to park the metering gear on.
Ok, set the panels up, put down some plywood and used a foldable table to make sure the panels are all at about the same angle.
Time 1345 PST
Latitude is 48.54 North.
Bright, clear, not a cloud in the sky.
Initial Panel Angle 60 deg (90 = vertical, 0= flat on the ground.)
Panels are aimed DIRECTLY at the sun, and slight adjustments are made as the sun moves west.
Inital current from the panel, and voltage across the tractor battery:
4.82a 12.15v with the tractor key on so the two 10 watt headlights pull some power from the battery.
Time 1400 4.8a 12.48v
Turned the key off to see what the voltage would do, and it shot up to 16.5v but the panels maintained 4.7 amps.
That works out to about 77 watts.
Whups! Turned key back on and went in search of something for a test load...
400 watt 12v pseudo sine inverter, 75 watt light bulb.
Ok, voltages back in the 'normal' zone.
Ran the inverter until the battery voltage seemed to level out somewhat.
Panels were outputting 4.9 amps, and 12.14 across the battery with the 75 watt light on.
Started messing with the angle of the panel.
At about 1410 hours, the current peaked at 68 degrees, 4.9 amps.
Dropped them flat. 1.1 amp.
Raised them back to 37 degrees, current came back up to 3.8 amps, battery now down to 12.1v.
Turned the 75 watt bulb off, and the voltage came up to 15v but the current only dropped by 0.1 amp.
Time, 1420. Tipped them vertical to 90, current back to 4.7 amps.
Rechecked for peak, got 4.8 amps at about 70 degrees.
To summarize, within about 25 degrees of optimum, the current only dropped from 4.7 to 3.7 amps.
Panel output at 16.5 volts (1.5v less than Maximum Power Point,) was 77 watts.
Soooo.... Near the end of January, at almost six degrees north of your position, at two hours PAST noon, I am seeing 77 percent of the rated output of the panels.
I'd say you have a wiring error, or bad panels.