pianotuna wrote:
Hi jrnymn,
Look at the 66 volt trace @ 12 volts it appears efficiency is 94% @ 400 watts. The very best is 97% @ 16.5 volts and about 125 watts.
To me that represents a spread of 3%.
At best for 400 watts it appears that the number is 95%. That represents a 5% loss to me. I.E. far more than transmission losses due to cabling.
This from the page you linked to--top graph called 12 volt conversion efficiency.
My limited understanding is that pwm has no conversion losses--because they do not convert volts to amps.
jrnymn7 wrote:
Pianotuna said,
"As voltage rises efficiency of the controller drops. If there is a long run from the panels to the controller some money can be saved by going to series, but there will be losses in the controller. One figure is 98% with nominal 12 volt panels, and 96% with double the voltage. I do not know how low the percentage may drop."
If I'm understanding the Tracer 3215BN's efficiency graph correctly, there is about a 0.5% drop in efficiency at 35v vs. 17.5v, using 280 watts. And at half power (140w), or even at quarter power (70w), less than a 1% drop.
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I'm not sure what 400w or 66v has to do with my 280w set-up??? But it does show that the mppt would not do as well with a larger 12v array.
I was under the impression MPPT controllers convert Vmp, not Voc. And the graph does say Maximum Power Point Voltage... not Voc.
And even if the mppt did convert Voc, my two 12v/140w panels, in series, would have a Voc of about 44v, not 66. And to obtain 66v Vmp, I would have to wire 4 such panels in series, not two. So back to the mppt not doing as well with a larger 12v array.
It appears the 3215bn would perform in the 95.75% - 97.25% efficiency range with two 140w 12v panels. I cannot speak as to the efficiency of say the Solar30 PWM, but I doubt it's 100%.
