Fridge on the ferry?

TonyOS

Hi,  in a couple of weeks we are going on the Portsmouth to Bilbao ferry.  I think it's a 36 hour crosing.  I was just wondering when other people have done this crossing do you leave you fridge turned on?  If I leave it working on battry for that time,
will it completly drain the battery or should i turn if off close the door and hope for the best?