Solar Cable Tangles

Hello; I have two solar suitcase panels that I set outside the RV. I run an 8 gauge solar cable out to them. I have a couple of sets of cables so I can add length if I need to, for a total of about 20 feet. Of course, each cable has 2 cables, a + and a -. My problem is that is a lot of cable and gets tangled easily.

How can I combine the + and the -? I thought about plastic wire conduit but even 1/2" isn't big enough for two 8 gauge cables. I also considered just using pieces of electrical tape every couple of feet but the tape gets crappy after a while. What can I do to avoid a tangle?

Thanks for your ideas.