ats the way I wired mine.
Shell (outside) negative (Bleck)
Center positive (Red)
My Aliner DC was wired with Bleck and White -- White neg. Bleck Pos.
I used a yellow fuse wire for inline fuse which I connected to the white positive. Then I added a on/off switch that had red and black wires to break the battery out of the converter circuit . Just recently sold it. Hope the new owner loves puzzles

It was wired wierd of that I am positive.
g
If it's not broken, you're not trying hard enough.