About two yeas ago I rode my bike to work and at the end of the day, the battery was fully drained. I replaced the battery thinking it was just failed. This happened again last summer, I took it to the shop and they say it was a loose battery connection. O.K. I can buy that. Well, it did it again a couple weeks ago and I left it to the winter. Well, got it charged and went to start it yesterday and dead again. WTF?????? Help.