I just bought a 2007 Honda metropolitan from original owner with 50 miles on it for 1000. Pink hibiscus. Garaged its whole life. It's immaculate. I'm replacing the battery and didn't see where one of the wires was originally. There was a double green

wire which goes to the negative, black wire with a red terminal end which is positive, and the mystery wire which is black with the black terminal. (See pictures...) where does black with black terminal go? Thanks