looking at your pictures it seems that the wires coming from the pack before the shrink wrap got the most heat and melted all the insulation off the wire. In my opinion this is the area in which the short occured that also caused the batteries to overheat and melt the pack. The other wire damage looks like it recived heating by being in contact with the melting battery and was not involved directly with the short. was the battery pack modified or have the connector soldered on as aftermarket?