How to wire 18, 100w panels to 48v CC

nschizzano

I have about 18, 100w. How should I wire them together to run intoa a 48v Charge Controler With a 150v max? And what cable awg would i need? I have 75ft length of copper 8awg ran already not sure the exact numbers to punch in the cable calculator to see if I need to change the AWG 

BB.

Need to know the Vmp/Voc ratings of your panels and your high/low temperatures to calculate Voc-cold of your array vs the 150 VDC Max input voltage... Working battery bank voltage (12/24/48)?

Guessing you are somewhere in the Northern US (South Dekota to Nebraska area???), and perhaps hit 10F to 0F as max lows in winter...

Without the "real" numbers, would guess you are in the 5-6 series panels per string (not to exceed 150 VDC in your cold weather).

5 panels in series, * 3 parallel strings = 15 panels total (out of 18)
6 panels in series * 3 parallel stringss = 18 panels total (out of 18)

You can also go for lower Vmp/Voc array voltage... Depending on battery bank voltage, and max controller input current... But you will be left with the factors of 18 limiting to how many panels in series/parallel you can wire up:

18 factors to 2*3*3 with a maximum of 5-6 panels in series to a minimum of 24 (12 volt) or 48 (24 volt battery) to ~72-96 volt Vmp (48 volt battery) bank (this is Vmp-STD standard panel specs estimated ratings for hot climates in summer)....

I.e. for a "lower/minimum array voltage"":

~24 volts Vmp minimum for 12 volt battery bank = 2 panels in series (Vmp-array ~ 36 volts)
~48 volts Vmp minimum for 24 volt battery bank = 3 panels in series (Vmp-array ~ 54 volts)
~72 volts Vmp minimum for 48 volt battery bank = 4 panels in series (Vmp-array ~ 72 volts)

18 panels / 2 = 9 parallel strings of 2 panels
18 panels / 3 = 6 parallel strings of 3 panels
18 panels / 4 ~ 4 parallel strings of 4 panels (16 panels total)

In general, the higher Array Voltage means lower Array Current and smaller (cheaper) diameter copper wire--And/or the ability to have a longer distance from array to battery shed with the least amount of $$ spent on copper wiring.

-Bill