Solar Panel Voc-MPPT?

BFL13 wrote:
The practical value of Isc for me is mostly for aiming the panel when setting up. It is aimed right when Isc is highest. If you can't aim your panel, then you would not be thinking of that usage.

Next is that with 12v, PWM you can get the "amount of amps" at the battery that is the same "amount of amps" as what you got for Isc (which can be any amount depending on the light and temp) Isc is your "expected amps." Rated Isc is your "expected max amps." Sometimes you can get more amps than that such as with cloud effect.

The Voc is just a curiosity. If it is low, that has no apparent relationship with how many amps you are getting at the battery.

Now with MPPT most of that seems to be lost in a swamp of moving parts with nothing to grab onto.

Thanks for those graphs. I don't understand them, but I hope to eventually, when "the light comes on." I'm sure it will--then I will wonder why I couldn't see it before. :(

for setup orientation, a clamp on current probe on one panel output lead would let you find the optimum angle/orientation. Quicker than running in and out of the trailer to read the trimetric battery current. Just orient for max current.

Since your looking at fairly low currents (<10A), it may be hard to find a low current hall device meter with the desired resolution, so an alternative would be to use a DMM with inline current measurements.

We've got sunshine this week, and I am going to do some experiements with my panels. I'll add an experiment to see how using a clamp on current probe to find max panel output works out. I'll be able to monitor MPPT input voltage at the same time and see how close just looking at current is to looking at current and voltage.


I'm going to guess that with an MPPT controller, if you find the point with max panel current, you will be close enough to finding the max power point that finding looking for max current and max voltage isn't worth the effort.