Hi Scooterjam ,
I think it depends how cold it gets , in your garage. I always charge in my garage but it does not get more than a few times a year below freezing . I live mostly in Holland .
When I am in Spain in the wintertime , my scooter stands outside on a sheltered spot , it hardly ever freezes there , but a few degrees below is no problem . As long it is a dry place it is allright for the batteries . But how much cold they can handle I don’t know .