Winter is coming, and I think my battery is dead/dieing

rww

3-7...as you can see u r my 1st reply, I read but never respond, so here it goes, as an old mechanic, I can tell you that people neglect their batteries. the z has lots of electronics and electrical parts...concur with the others 5-6 yrs....lucky you...here in the Midwest where temps drop to subzero my routine is simple ...every fall, on all cars, pull the clamps off the posts and clean with a post wire brush....terminals and clamp...oxidation needs to be removed...twice a month I put a charger on over night, subzero...maybe wkly..short drives will slowly drain it and the chemical reaction in a bat is temp dependent, if replacing, I concur with barncobob, go to Walmart, and get the best bat, highest cranking amps, in the specific size..watch for post location..which means take yours in....charge over night..if u don't have a charger, well get one ..lastly, feel lucky, our Z is garaged in the winter