Even if the battery was new last fall , A funny thing about battery is you can only let them go dead couple times before before they are shot all to hell, i know this because it happen to me , so i would say it shot all to hell, that been said you put the car up for the winter, i do same thing but you really need start it once or twice a week win put up, Ok i would say it as simple as you need a new battery and then Drive it !!!!!!!