I've jumped mine from the leisure battery before if that still has good charge you could try that (although I am sure someone will explain why you shouldn't[:0]). You might find cold weather means your battery loses charge quicker. I always disconnect the battery when I park it up at home as I think we had something trickling power out when parked up as only held charge for 3weeks or so and a new battery didn't fix it. As ever best thing is to drive it often
good luck.