Solar panel wiring
I'm rebuilding a Class C and I might be redoing the roof soon. I would like to run the wiring for solar panels now instead of doing it through the fridge vent later. The thing is that I won't be able ...
Forum Discussion
westend wrote:
I don't think you've calculated the voltage drop correctly. I'd bet you are dropping voltage 3-4% over 40' of 10 ga at 54V w/17 A.
A better practice may be to install the largest wire possible from the roof to the controller location. That will insure that all the current produced gets to the controller.
yeh.. I messed up, I'm tired and have had a few beers..
here is the revised calculations.
The resistance per foot from the standard AWG tables is 0.9989 milliOhms per foot for 10AWG copper.
my panels Vmpp is 18.8 V and I have approx 40 foot run inclusive from panels to charge controller.
so assuming I could actually get 160W from each panel on a perfect day then: as a 3S2P string I get 18.8V*3 = 56.4 Volts from each string. (160W*3)/56.4V = 8.51 Amps. with 2P = 8.51*2 = 17.02 Amps
therefore: 40ft * 0.0009989 Ohms * 17.02 Amps = 0.68005 Volts drop
0.68005/(56.4/100) = 1.2%
you lost the bet.:p
