Winter storage, battery too week to start. How to charge?

Can you take the battery out and bring it in the house? Maybe bring them all in and put them on a charger. The cold is hard on batteries especially if they are not charged. As far as the rest of the rig, I would leave it alone until spring. I know you are supposed to run the generator once a month but I think I would wait for spring. We are a couple hundred miles south of you so we know what your going through. Come on summer!