Solar Controllers--Don't be a Sucker! :(
Just got to say it again, how it is we are sitting here for five months off grid on solar with no problems at all (third season on solar like this), using the non-programmable, non-MPPT, solar control...
Forum Discussion
Mark, the mppt manufacturers got you well trained. Your calculation has several errors. The pwm scenario does not use Imp (5.70A), but rather a current that's very close to Isc (6.10A). That means the pwm power output isn't your calculated 77.52W, but 82.0W.
The second problem is that under normal conditions the panel will not output 100W in mppt mode, but it will output 82W in pwm mode. Let's say this panel is 1 m^2 in area. To output 100W, it needs to be irradiated with 1000W. The panel is only 17% efficient. That means close to 800W goes to heat your panel. Your panel will get hot! The panel will lose power at the rate of -0.38W/C. A typical temp rise is 30C, meaning the panel is now at 88.6W.
MPPT gain is now 9%. Subtract 2% mppt efficiency and you're down to 7%.
Sal
The second problem is that under normal conditions the panel will not output 100W in mppt mode, but it will output 82W in pwm mode. Let's say this panel is 1 m^2 in area. To output 100W, it needs to be irradiated with 1000W. The panel is only 17% efficient. That means close to 800W goes to heat your panel. Your panel will get hot! The panel will lose power at the rate of -0.38W/C. A typical temp rise is 30C, meaning the panel is now at 88.6W.
MPPT gain is now 9%. Subtract 2% mppt efficiency and you're down to 7%.
Sal
msiminoff wrote:
- Power (W) equals Volts (V) times Amps (A) **
- Solar panels make their most power (W) at a specific voltage (V) and current (A). Manufacturers call this the "Maximum Power Point". In the case of my Grape panels the value is 17.7V and 5.70A, that's the Vmpp and Ampp respectively... So 17.7 x 5.70 = 100.89W
- If a PWM controller is used, then the solar panel's voltage is forced to match the battery voltage (example 13.6V). Again, using my Grape panel as an example... 13.6V x 5.7A = 77.52W. That's a (theoretical) sacrifice of 23 Watts of available power.
