Solar fuseing, confuseing
Were installing a Renogy 400 watt solar system on our fith wheel. We stay on our property about two months in the summer up near Canada in Washington.Anyway this is the kit I bought. Mind you I'm comp...
Forum Discussion
BFL13 wrote:Ed_Gee wrote:
Your figures are not in dispute. The problem is you continue to ignore that a PWM controller CAN NOT use the full power rating of a solar panel. My panels for instance have an operating voltage of 18 volts and a maximum power current under load of 8.88 amps....giving each panel a specified rating of 160 Watts at maximum power point , which occurs at 18 volts. A PWM charge controller wastes any voltage (as heat) that is above the battery under charge voltage. The MPPT controller does NOT waste that excess voltage, and is using the full specified wattage the panel is capable of putting out. These facts have nothing to do with the operating conditions or temperature of the panel but have everything to do with the way MPPT uses the panel's full potential over the PWM controller.
PS: even given your resulting conclusion to be accurate, I certainly would not consider an extra amp of charge current to be " teeny weeny " ..........for my particular installation that is over two extra amps per hour per day's charge and can be quite significant for some RVers' boon dock operations.
You seem to believe in the MPPT salesman's pitch that they use the panel's power but the PWM "wastes" power.
The claim is based on the output power for PWM compared with panel rating. Since you agree with my figures, then looking at the 13v situation--- output 16a x 13v = 208w for the 255w of panels.
Wow! It is "wasting" 47 watts. Meanwhile, the salesman says the MPPT is using it all. :)
OK, so the output there is 16.9 x 13 = 220w. So the MPPT is "wasting" 35 watts!!!! But, but, that can't be true! Call Security.
You continue to compare apples to oranges. Out of exasperation I will not try to point out your error again but instead will simply point out what you just said above. It appears that you do not deny that the MPPT controller in your own example above can use 12 more watts of panel energy per hour than your PWM example. 12 Watts in a six hour solar day is 72 Watts per panel per day more than the PWM controller can use. With three panels that would be about 215 more Watts per day. Thank you for confirming my original comments about the superiority of MPPT controllers over PWM.
