electrics

Went out to start the bike this morning, chugger, chugger, chugger, turned over well (optimate on the battery), but wouldn't start.
After some more trying smoke started to appear from under the tank, took the seat off, hinged the tank up to find the neg terminal lead connected to the battery had melted the rubber shroud that insulates it and was melting the casing of the cable.


Any clues?