I have a 2017 sunset trail 331bh and I took the battery out for winter and I didn't pay attention when I unhooked it. It has 3 wires that connect to the battery (red, black, and black with white stripe) I know, of course, that red is positive, and black is negative, but am unsure as to whether the black with white stripe wire is positive or negative, and what it is even for?
Another way to go about it if you have a continuity tester.
Touch one probe to a bare spot of steel on the frame, then touch the other probe to the ends of the wires. One at a time. When you find the ground wire you should have a full meter of continuity.
Just make sure to do this when the batteries are not connected and the AC power is not connected.
2008 Cruiser CF26RK
2013 Ford Eco-Boost
Heavy duty payload - Max tow
Look around on the tongue for a sticker. Late models have been black for positive ( yes!) White for negative (return). Like house wiring. The red you have is probably a positive hot wire to an accessory, like a tongue jack.