Solar-Panel to Controller Loss
Much has been made of the lower losses on the panel to controller path with MPPT because the amps are less. So once you have your loss measured, how valuable is it to improve on that if you don't lik...
Forum Discussion
The 60-cell panel Vmp = 31.26V. The question is: at what temperature does Vmp drop to 29.6V. I'm saying Vmp is at the edge of the IV curve cliff and therefore a valid interpretation where the controller can't output 29.6V.
Did you say you had 1.7% line loss between panel and controller?
Controller input voltage after line loss is:
Vin = Vmp * (1-1.7%) = 30.73V
Now we calculate the temperature rise that causes the voltage to drop from 30.73V to 29.6V. Vmp temp coefficient = 0.4%/C
Delta T = (1- (29.6V / 30.73V)) / 0.005V/C = 9.2C
At 34.2C (25C + 9.2C) the controller will have difficulty supplying 29.6V to the battery.
Did you say you had 1.7% line loss between panel and controller?
Controller input voltage after line loss is:
Vin = Vmp * (1-1.7%) = 30.73V
Now we calculate the temperature rise that causes the voltage to drop from 30.73V to 29.6V. Vmp temp coefficient = 0.4%/C
Delta T = (1- (29.6V / 30.73V)) / 0.005V/C = 9.2C
At 34.2C (25C + 9.2C) the controller will have difficulty supplying 29.6V to the battery.
BFL13 wrote:
The question is how high must panel temperature be so you can no longer get the 24v battery to say 29.6v ( twice 14.8)?
