I am running 400W(2x200W in series ) at 45V through a Morningstar 15A MPPT controller. That is 100% over paneled. Their documentation says the controller will protect itself and limit output current to 15A no matter how many Watts are input at under 60V. I know do give up Amps when I hit the 15A limit.
In contrast, this 150% limit in Epever seems like some king of design deficiency.
My 4kW array maxes out at 3kW of Microinverter capacity and I’ll usually just touch upon that limit in the middle of a bright, clear, high-production day.
So I’ve been assuming 75% of panel rating is a realistic maximum to plan for if ifon’t want to waste power by saturating the SCC.
75% of panel rating would mean I’d want 0.75kW of SCC capacity for 1kW of panel rating or alternatively, if I want a peak of 1kW of SCC output, I’d need to overpanel with 1.33kW of solar (33% overpanelling).
A few members here told me 75% of rating seems low, so I’ve dug more deeply.
First, the actual max I’ve seen out of my 4.02kW array is 3.36kW, not 3.0kW, so that is 83.6%, not 75%.
Second, my Microinverters have a conversion efficiency of 95.5%, so 3.36kW out means 3.53kW in, or 87.5% of rating.
And finally, these panels are now 5 years old, and guaranteed to have <= 3% degradation on their first year of service and <= 1% degradation per year of service after that.
So if I assume my original 4.02kW array rating has degraded by 7%, that translates to an adjusted rating of 3.7386kW and my peak output represents 94.4% of that adjusted rating.
So I’m not as hungry-ho about overpanelling my SCC as I once was.
The minimum overpanelling I want to plan for is 1/94.4% = 6% and if I think I can afford to spill the first few years of peak production, the maximum overpanelling I’d be comfortable with is 1/87.5% = 14%.
I’ve not yet had any clear explanation from a vendor what the paneling limit in their specifications actually translates to. As long as they can drive the voltage all the way to Voc, they should be able to choke off any size PV array.
They are certainly concerned about their customers not ‘wasting energy’ or ‘wasting money’ so it may be nothing more than that.
Or it could be that there is a minimum granularity on voltage control that gets too abrupt when array input power gets too large.
Or it could be that these cheapo controllers cannot run for a full 8-10 hours at their maximum current rating so they use limitations on array size to assure they will only be at peak output levels for a shorter portion of the day...
In any case, I appreciate the datapoint, though so I am less interested in overpanelling than I was when I started the thread..,