HickoryValley

I’m looking for recommendations on how best to store the batteries for my Ryobi RY48ZTR100. I live in southern Michigan so it can get cold in the winter. My garage is not heated so what I have done in past winters is remove the batteries and store them in my basement. Removing the batteries and moving them to the basement is a lot of work as is doing the reverse in the spring. Does anyone have experience using battery warmers or other techniques for wintertime storage? Michael