I bought battery maintainers for all of my equipment that Winters in my outdoor shop. Mower, tractor, generator, truck, and so on. They are potted, all enclosed and electronic, I think I got them at O'riley or NAPA.
I've done this for the past many years, keeps the battery fresh and topped off. You might want to put Stabil in your gas tanks and run the engines to get it in the carb's also.