mppt vs pwm

jrnymn7 wrote:
"I'm seeing two 150w panels in series only producing a few amps more than my 245w panel. On a better controller I know of a 960w system using 160w panels in pairs for mid 40's producing 48a while I would expect 60a from four 250w 24v panels."

That sure seems counter-intuative. One would think the 12v's in series, having a higher combined Voc, would result in even more wattage being used by the controller. I can see if the mppt was rated for 50v, and you threw 46 volts at it, but most buck converters boast ~98% efficiency, when operated within their duty cycle.

Does it perhaps have to do with the 12v 160w panels being in series, and thus their output would become 160w / 44v = 3.6a, as opposed to ~9a Isc?

A few times now I have seen mentioned on the solar forums that converting down from higher Voc to lower voltage is inefficient and I see the results in what people are getting out of their systems. Basically the more balanced the Voc and Isc is, the better. It takes both and having one go up without the other doesn't produce the results you would expect. My 220w panel shot to over 40v on a cold day but there was no current. When it did settle down but was still at a higher Voc it only added 3/4a to the system. Taking it up in altitude would increase both Isc and Voc for a better result.

In photography the sweet spot of a lens is the aperture that it is it's sharpest. In Rc airplanes it is a combination of airframe, motor and prop. Find those sweet spots and the difference can be night and day. I believe that as more of us use and report on our solar that we will find that there are different outcomes depending on our choices. Not that anyone is right or wrong as long as their needs are met but rather that a person looking to build can see the differences in the choices and build to their needs.