I'm rewiring some 2"x2" solar panels, I see the place the wires are supposed to be connected, and they're marked with a "+" and a "-" sign. I look through my bin of wires, and see a bunch that will work for me (two wires joined together so that one is positive and the other negative).
However, some have a black wire and a white one, some are black and yellow, some are yellow and black, red and white, both the same... In the case that they are both the same color, I've marked one wire myself.
Is there a standard for which color should be positive? For example, you have two wires that are the same color, but one is knotted at the ends. Is there a standard that says something like "the knotted one is always negative" or "red is positive".
I know that if there is a high risk involved, then I shouldn't make an assumption, but is there a "right" way?