Mate it's probably nothing! I leave both EPs on the drive while I'm away at uni, Got back after 2 months, NA battery had died. Jump started, took it for a 10 min drive to get some petrol, wouldn't start. Gave the starter motor a tap with my wheel brace, juimp started again, took it for a good 30 minute drive on the motorway. Started everyday for a week fine! It's just the cold weather would have affected the battery, and a short drive won't charge it enough!