dissconnected wire

just checked and found a dis connected wire black/with a yellow stripe under the battery towards the gear box looks like its broken from somewhere but i cant see where it fits its a automatic any one know where it fits its a thick cable i think it could be a earth wire but not to sure does any one know where the earthing points are
Its the earth wire. From the battery it goes to beneath the battery tray and from there it continues to the gearbox if i remember correctly