I see your recent recommendation in Tech Talk articles to use 10/2 wire to connect a solar panel at approximately 10’ length. Why would I use heavier wire than that which comes from the factory? It would seem to me that the lesser wire provided (along with factory connectors) would be a limiting factor, as well as, the maximum amperage generated by the solar panel. So why is a larger wire suggested for transmission?
A 10/2 cable is made of two #10 gauge wires. It does not refer to the length. Commonly, the solar panel on a boat is located a fair distance from the batteries. To offset the line resistance, it is advisable to install a larger gauge wire, i.e. #10, to help minimize the line lost. When choosing a wire, you should always take into consideration both voltage drop and ampacity. Also, you can interconnect a larger wire with a smaller wire using a step-down butt connector.