I like to use 0.77 for panel and controller deratings--Remember there is ~5% MPPT controller drop and 1-3% typical wiring drop too (not clear if 4.8 kW includes those losses or not)...
Ethan Brush wrote: »
Ok lets here it. What is the most AC power you have seen relative to your array nameplate? OR for off-grid I'll take DC charging watts if known.
BB. wrote: »
Just rough numbers... Assuming warm sunny days (9 months of the year). We are probably taking about a 77% to 85% range of typical maximum output at noon.
If the panel orientation to sun are off by 10 degrees, Cos 10 = 0.985 (98.5%), add a percent or 3% for wiring losses, 5% for charge controller losses (MPPT), 81% or so for slightly dirty panels at sea level, etc... 5,000ft with clear/cold sky, etc... you may get closer to 85% panel ratings. Tilt the panels vertical, throw a field of snow in front of the panels, sub freezing day, you may get >100% of rated output of the array.
We can go through the math of the panels and system if you wish... But for planning systems, quickly and with a minimum of fuss and confusion, using conservative numbers (not too conservative) gets us close enough for most installation (usually within 10% of actual output).
BB. wrote: »
For PWM controllers and panels... They operate differently.
The Vmp-operating of the array is basically the voltage of the battery + voltage drop of controller + voltage drop of wiring... So as long as Vmp-array is > than Vbatt+stuff -- then that is all that matters.
Since the panels are (for the most part) current sources where the current is proportional to the amount of sun hitting the array (100% sun, then 1.00 * Imp, 50% sun then 0.5 * Imp, etc.--usually pretty linear to within 5% or so down to indirect sun on panels which gives virtual zero useful current do to internal leakage current), the output of the array is only limited by sun, haze, dirt on panels, etc. And Imp of the panel rises (slightly) with temperature (cold panels produce slightly less current)--In the big picture, the voltage temperature effects swamp the current temperature effects.
The only time Vmp-array "matters" is when you have Vmp~17.5 volts (Standard conditions), and a full/equalizing battery bank (perhaps a bit cool) that is running 15.0+ volts... A warm panel, with the 20-30 C cell temperature increase due to sun/poor cooling by air/wind, then Vmp-array-hot falls to or slightly below Vbatt+stuff--And current can fall. Usually not a problem--But with extreme conditions/heavy loads, a MPPT controller + Vmp-array >> 17.5 volts can be worth the extra costs for a MPPT charge controller.