Originally Posted by Jon Hacking
If you're trying to control 60A, you've got multiple panels
. Running them in parallel means that if one gets even a little shaded, it won't be able to reach the MPPV of the other strings, so it will simply drop out of production. But if each series string of panels
is feeding its own MPPT
, then such a drop in voltage can still contribute meaningful current
to your batteries
. And multiple small MPPTs is often cheaper than a single
large one (certainly was in my case).
I don't have any issue with multiple controllers, other than that if you're retrofitting, you might have to do some rewiring - which might be challenging.
However in extensive conversations with the tech guy at Blue Sky (mentioned up-thread) he recommended the cure for parallel issues like that by insertion of a blocking diode into the MC4 stream positive legs.
From my correspondence of the time:
couple interesting articles:
Here is an article about combining multiple panels, although it does not mention blocking diodes in particular, notice what happens when you combine multiple panels in parallel with different voltages:
Connecting Solar Panels Together to Increase an Arrays Power
So, I did that; My positive legs have the diode inline before the parallel junction for the two panels (360W Sunpowers). I don't actually have shading issues, but it can't hurt in the event my KISS wind generator
MIGHT shadow some of the lines of cells enough to make a difference...