Quick Test of Eco-Worthy MPPT Controller
Ordered it on 3 Oct arrived at the door 23 Oct free shipping. Controller rated to 42V so watch that. EG I have it on one 230w panel, Voc 37v at 25C, so would be more Voc at cold temps. Not ab...
Forum Discussion
Using the coefficients is an interesting approach, thanks.
Does that calculation using V take into account how the temperature coefficient for P is greater than for V? If PWM doesn't care much about P and MPPT is all about P, then is it valid to compare them using V?
Where PWM is all about I, which goes up with temperature, and MPPT uses V which goes down with temperature, can they be compared for amps to the battery if you know the temperature and the panel specs?
Let's see----
I often see the Sharp 130w panel when disconnected and aimed showing
Voc- 20.3 (rated 21.9) and Isc 8.3 (rated 8.2)
It should be possible to derive the panel temperature from that using the coefficients. Voc is -0.36%/C and Isc is + 0.053%/C on 25C
21.9-20.3= 1.6 and 1.6/21.9 is down 7.3% and 7.3/0.36 = 20.3 so panel temp was 45.3 (spec NOCT is 47.5 as it happens)
Using the amps side to confirm, we get:
8.3- 8.2 = 0.1 and 0.1/8.2 = up 1.22% and 1.22/0.053 = 23 so panel temp was 48
So that sort of works out. Now knowing that, what would we get for P using the 230w panel at 46.5C ?
Spec says coefficient for P is -0.45%/C on 25C we are up say 21C so P would be down 21 times 0.45 = 9.45% of 230w =21.7w so P is 208.3
If battery is 13.5 then 208.3/13.5 = 15.43 amps
So that ought to mean when I am getting 230/130 x 8.3 = 14.68a from PWM I will get 15.43a with MPPT. Hey, that's a whole entire 0.75 amp!
But with the PWM 12's IV curve that 8.3 will be down to say 8.1 at 13.5, so that means 230w would be 14.33a. diff is 1.1 amp
So what would it be at batt 13 and 14? where Isc on the 130 would be 8.3 and 8.0?
13v- 208.3/13 = 16.02a vs 14.68a diff of 1.34a
14v- 208.3/14 = 14.88 vs (230/130 x 8) 14.15 diff of 0.73a
So I am not getting very excited here about how MPPT will be better than doing it with PWM.
It would depend very much on relative costs and that could be anything where some places you can get 24v panels way cheaper than 12v panels/watt but the controller costs more, or where the panels are similar in cost/watt. Prices are all over the map.
Does that calculation using V take into account how the temperature coefficient for P is greater than for V? If PWM doesn't care much about P and MPPT is all about P, then is it valid to compare them using V?
Where PWM is all about I, which goes up with temperature, and MPPT uses V which goes down with temperature, can they be compared for amps to the battery if you know the temperature and the panel specs?
Let's see----
I often see the Sharp 130w panel when disconnected and aimed showing
Voc- 20.3 (rated 21.9) and Isc 8.3 (rated 8.2)
It should be possible to derive the panel temperature from that using the coefficients. Voc is -0.36%/C and Isc is + 0.053%/C on 25C
21.9-20.3= 1.6 and 1.6/21.9 is down 7.3% and 7.3/0.36 = 20.3 so panel temp was 45.3 (spec NOCT is 47.5 as it happens)
Using the amps side to confirm, we get:
8.3- 8.2 = 0.1 and 0.1/8.2 = up 1.22% and 1.22/0.053 = 23 so panel temp was 48
So that sort of works out. Now knowing that, what would we get for P using the 230w panel at 46.5C ?
Spec says coefficient for P is -0.45%/C on 25C we are up say 21C so P would be down 21 times 0.45 = 9.45% of 230w =21.7w so P is 208.3
If battery is 13.5 then 208.3/13.5 = 15.43 amps
So that ought to mean when I am getting 230/130 x 8.3 = 14.68a from PWM I will get 15.43a with MPPT. Hey, that's a whole entire 0.75 amp!
But with the PWM 12's IV curve that 8.3 will be down to say 8.1 at 13.5, so that means 230w would be 14.33a. diff is 1.1 amp
So what would it be at batt 13 and 14? where Isc on the 130 would be 8.3 and 8.0?
13v- 208.3/13 = 16.02a vs 14.68a diff of 1.34a
14v- 208.3/14 = 14.88 vs (230/130 x 8) 14.15 diff of 0.73a
So I am not getting very excited here about how MPPT will be better than doing it with PWM.
It would depend very much on relative costs and that could be anything where some places you can get 24v panels way cheaper than 12v panels/watt but the controller costs more, or where the panels are similar in cost/watt. Prices are all over the map.
