Wire Gauge Required Question
For some reason I just can't understand the various wire gauge tables, and I have tried to, so I am hoping somebody will take pity and do all the work! :) One table that I can follow says that for...
Forum Discussion
BFL13 wrote:
Got it, thanks. Ok so now you run into that business about the MPPT controller having a harder time to make 12v to the battery when the input voltage is so high?
Story being it gets inefficient over 50v input. So my question was why not use two controllers to split the work?
Mostly, it's high amps in battery cable that make it hard. Because when you have, say, 3*230W array, you have 45A @14V output, and 45A create a huge drop in volts, watts and AH on every darn foot. To avoid this drop, you have to buy a monstrous #4 or #2 cable and keep it short.
Yes, MPPT conversion efficiency drops with higher input voltage. Higher voltage would cost you 4% of power in the middle of controller range. In controllers like Rogue and Tristar efficiency drops from 97% @30V input to 93% @90V in the middle of max amps, more at lower amps, less at higher amps. In your Guangdong black dog - don't know :)
In light of these other losses, the difference in losses of #10 array cable VS #8 cable looks very, very small.
