I have 8 175 watt 21.6v 9.73a panels 2 series 4 strings, So is the combined voltage of my series panels used? Each panel is 21.6 open circuit voltage x 2 = 43.2v. So do I use 43.2v and 1400w for the voltage and watts for sizing CC.
So the 150/85 would be sufficient? Or would 150/100 be better?
I checked SCC sizing calculator and found confusing info. 150/85 it is 117% oversized and150/100 is 97% undersized. Could someone clarify this for me?
Thanks
You are correct, the panel Voc 43.2V and power is 1400W.
Based on your numbers you have a 12V system so absorption voltage will be say 14.2V, so theoretical max power output for the 150/85 is 14.4 x 85 = 1,224W so the panel is oversized. Often you do not get full solar radiance so most of the time the 85A version will be providing as much power as is available and for a few occasions it will limit the power in full sun on a clear day at noon. The 100A version can handle 1,420W so the solar panel is slightly undersized but it it so close that it does not matter and during charging the controller will not be a limit.
We need to know your system battery voltage to give you specific help here.
But you have 8 x 175W = 1400w, I assume you used STC values.
Charge amps are based on battery voltage. Since watts is volts x amps.
For 12v system that is 1400÷12v that is 116A at 25°C. So a 150/100 would be slightly oversized at lower battery voltages but correct at 14v. Since 14Vx 100A = 1400W
For 24 v it will be 58A charge current
For.48v it will be 29A.
The higher the battery voltage the less amps.
I would use 2 strings of 4 panels on a 150/100. Much better solar performance then.
Or better heat a 250/100 and one string. (Less wiring and switchgear.)
