Solar question
I am working through the solar deal hopping to have something in place for the spring. Right now I am looking at 200 to 250 watts worth of panels that I can expand in the future. Just so I understa...
Forum Discussion
pianotuna wrote:
.......BFL13 wrote:
And BTW the "urban myth" about MPPT doing something in low light vs PWM has not been seen by me with both running at the same time when I had both set-ups. In fact for most of the summer the MPPT has under-performed PWM due to higher panel temperature lowering panel voltage so get fewer amps with MPPT than would with PWM.
I don't agree. What is happening is that the input voltage is too low for summer time use. If the system is 33 volts the opposite may be true. In fact the higher the input voltage for MPPT the better, for hot weather use. There will be as a result slightly greater losses at the MPPT controller (98% down to 95%)..........
Not understood, please explain. My 230w panel rated for 37voc is doing about 34voc with panel temps at 51C, ambient temp 25C and loses about 10% output seen as amps compared with ambient 16C and panel at 44C.
I have observed about 13.5amps MPPT instead of 14.4a PWM this summer. I got 15.5a vs 14.4 last Spring. It is now coming back some. Today with ambient 18C and panel temp about 45C I saw 14.X amps, so this confirms it is not panel degradation or bad wiring or whatever, it is all about temperature. Also that fits with the standard info on MPPT that you lose 10% output (however measured) when panel temp is 50C vs 25C.
( no idea what ambient would be to get only 25C panel---freezing out?)
I don't understand how more rated output voltage would do better proportionately. Temperature is temperature.
