Plus the salt doesn't get washed off the roads until a couple of good spring rains. I have garaged my ragtops for 35 years and have found that the best thing is to go out and start up the car every 2 weeks to keep the battery charged. I have a battery minder and mine never seemed to work. Someone else said they did that and it worked fine. In any case batteries don't like to go to zero charge. If you do let them go down, plan on replacing them in a year or two at max.