Originally Posted by peterh
A bit late to point his out now, but had wired your solar
panels in series (charge controller wired to panel one, panel one wired to panel two, then panel two wired back to the charge controller) instead of in parallel (charge controller wired to both panels one and two, then the panels wired back to the controller) you could have gone with 14g wire and had an almost identical drop in current. Unlike older Pulse Wave Modulation (PWM) controllers, most most modern Maximum Power Point Tracking (MPPT) controllers can handle two, sometimes even three or four panels wired in series, and wiring them in series increases the voltage and watts carried by the system without increasing the loss-inducing current.
Yes, I read about that option. There are a few drawbacks to doing it that way. I don't recall all of them, but partial shading is one, and smaller arrays are not ideal for series wiring. I weighed it out and selected parallel. I can also only use one panel if conditions are right. Parallel wiring the output current doubles too, but you need the big wire to keep the waste down. I think my 8 gauge wire loses about .2V with the 30 foot reach. The panels produce about 18v, so still plenty to work with.