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:
Hi BFL,
At what voltage does your mppt start to charge? Does the panel go from zero volts to 37 instantly?
What is the voltage loss per degree C as temperature increases?
Do both the mppt and pwm systems start to charge at identical times? Or does the mppt start sooner? (and correspondingly stop later?)
I don't have all that info, but I did note when first exposing a cool 37Voc panel to the sun it got 37Voc and then right away you could feel the panel warming up and watch voltage drop to about 34Voc whatever.
The voltage and Isc coefficients are listed in the specs for the panels but they are similar between 24v and 12v poly that I have had.
The key to it all is that voltage goes down when temp rises but the amps actually go up a bit. Since PWM gets Isc, this means you still get all your amps even when the Voc has dropped Also for MPPT, note that the power drops along with voltage because the voltage has a greater effect on the power than the amps.
I have not seen any difference in start or stop of charging times. The start depends on how much cloud there is over the sea and mountains to the East at sunrise as to when you first see the sun get above those. By then it is light out but panel amps are still low. The sun here goes down behind trees to the West so it is still light out but the sun has gone down. I turn my panel East then, ready for sunrise next day.
