2006 Dodge Stratus Battery Problems

Hello,

I have a 2006 Dodge Stratus V6 Auto sedan with about 140k miles. A couple winters back the battery seemed to be getting weak, was taken to an auto parts store to be checked and was replaced. It seemed to be fine for a couple of months, but once we got into the colder part of winter it started acting up again, eventually dying very quickly ( would start with a slow crank after 2 days, no lights on the dash after 3 days ) I had no luck finding the draw myself, with the battery of the Stratus being in the wheel well and motivation to work outside in New Hampshire winters being nil, I took it to a mechanic who also found no parasitic draw, and thought it was the battery. Soon after temperatures warmed up, the car could sit for weeks at a time without a problem, and it was forgotten about. The next winter comes, the battery starts going dead again, and i take it to a new mechanic who also couldn’t find any draw, and the battery was replaced again, under warranty. All was fine for another couple months, but again the battery started going stone cold dead after 3 days, dropping well below 12 volts. It is very consistent in the cold months, barely starting after 2 cold nights ( starting it once it’s warmed up to about 30 degrees ) and in the summer it doesn’t seem to drain at all, after parking the car last Wednesday the voltage stayed at 12.3 from last Thursday until this Thursday. With winter coming soon I would appreciate some guidance. Could it be that the 2 new batteries in the last 18 months were bad, is there something that can draw on the battery only during cold weather, or is there something I’m missing entirely? Thank you very much for your time.