Solar Panel Voc-MPPT?
Wondering if there is any relationship between measured Voc and MPPT performance with a 24v panel. My 12v panel has a Voc rating of 21.9 and Isc of 8.2, but I often see 8.2ish when Voc is only 20....
Forum Discussion
BFL13 wrote:
Since this is not the other thread, I can ask! :) When you swapped controllers in that ten minutes it took, what were the before and after amps???
I see you get better amps with MPPT and the panels in series, and that you had to put the panels in parallel for the PWM test, but somewhere in there, did you get a sequence of MPPT series, parallel, and then PWM amps? ( I suspect you did but did not want to spoil your report with such a distraction) Dying to know. :)
BFL, good catch.
for the MPPT vs. PWM comparison, I hooked the panels in parallel. (series makes no sense with PWM) and measured the output current with the MPPT controller and the shortest cable configuration. This test was on a different day(October 16th) and I wanted to do a baseline test to make sure I was seeing close to the same solar conditions are the previous day.
And yes, I did leave out what I was seeing with the MPPT controller, thanks for the catch. Wasn't intentional, just an ovesight going through all the data. I'll update that post. what I saw was 10.4A from the MPPT controller as measured by the trimetric. I didn't check MPPT output voltage, for this test current is what I was primarily concerned with. I wanted to make sure the panel was operating near Imp so when connected to the PMW controller I should end up between Imp and Isc where I suspected I would see the strongest influence from increased resistance.
I then quickly (if you call 10 minutes quickly) swapped controllers and measured PWM baseline converter with short cables at 9.5A as in the post. quickly hooked up the 90ft between the panel and controller (that takes about 30 seconds) and recorded the 9.0A.
Once done, I then reinstalled the MPPT controller, removed the 90ft of cable and looked at MPPT current on the trimetric. It was 10.3A. A verification that solar radiation didn't change signficantly between the beginning and end.
Solar power may have varied somewhat during the test, but previous monitoring beforehand showed currents to not vary by more than 0.1A over 5-10 minutes.
In test (2) and (3) I did a direct series vs. parallel ultra short cables MPPT comparison and basically saw the same results in output current for both cases of 10.3A.
