JustPractical
New Member
- Joined
- Aug 31, 2021
- Messages
- 106
Looking to use Znshine 365Watt Mono half cut cell panels (Vmp=34.0; Imp=10.74; Voc=40.8; and Isc=11.33). I’m feeding a Growatt 12kw (has two PV inputs rated at 250V each) attached to 4 x 48V x 100aH batteries.
I want to run 4 strings of 5 panels each (5S4P), (to get me 7200 watts - yes, the thought was to overpanel since it tends to be overcast on MANY days), BUT…5 panels in series comes to 204V, but if I “derate” for coldest day in 100 years (-39 degrees), that brings that voltage up to 255. If I derate for coldest day I have seen (-19) it comes out to 247V. Is this “close enough, good enough” or is it more like, “You are already way to close…want to be at 200 at most” or something in between?
Important fact – my roof slopes East/West, so my plan was to run west strings to one PV input, and East side to the other. I had it in my head to try and put the same amount on each (no reason, just assumed it was the thing to do.) If I did 4S5P My voltage would be 163V or 204V on the coldest day, BUT I have no idea where to put the fifth string – east roof or west roof? I would rather do the 5
I’m new to all of this, so yell if math is wrong, I used wrong numbers, or if there is a better idea. We plan to only be in this house for another 3.5 years, and mostly sized everything just to keep the heat on and the water running.
I want to run 4 strings of 5 panels each (5S4P), (to get me 7200 watts - yes, the thought was to overpanel since it tends to be overcast on MANY days), BUT…5 panels in series comes to 204V, but if I “derate” for coldest day in 100 years (-39 degrees), that brings that voltage up to 255. If I derate for coldest day I have seen (-19) it comes out to 247V. Is this “close enough, good enough” or is it more like, “You are already way to close…want to be at 200 at most” or something in between?
Important fact – my roof slopes East/West, so my plan was to run west strings to one PV input, and East side to the other. I had it in my head to try and put the same amount on each (no reason, just assumed it was the thing to do.) If I did 4S5P My voltage would be 163V or 204V on the coldest day, BUT I have no idea where to put the fifth string – east roof or west roof? I would rather do the 5
I’m new to all of this, so yell if math is wrong, I used wrong numbers, or if there is a better idea. We plan to only be in this house for another 3.5 years, and mostly sized everything just to keep the heat on and the water running.