consider the following,
1 they may have been hooked up to a GPS / Laptop or simmilar device, reqireing direct power from the battery (not fused). try & get hold of previos owner, this would help. Some times starter motor/s/relays are added for a winch, to winch your boat up onto a trailer etc. usually they are your regular type of heavy duty cables though. have u got a tow bar @ the back, this may give you another clue. if it's nor interfering with the way the car runs, tape them up & time will probily tell.

Good luck
Graham