A simple Battery Tender is what you need!!
Do what we all do here in the Northeast .... Connect up a simple little "Battery Tender" when the car is not in use. I guarantee you won't have any battery starting problems. I leave my battery in my car, with the Tender connected all Winter, also storing motorcycles that way for years. It's the correct solution to your problem. BTW ... Motorcraft Batteries are easily the BEST and the same price as Wal-Mart (or very close). I easily get 8 + years with all the Motorcraft batteries.