It does, but the Volt's already taken care of it. It is already engineered to enforce about a 20%-85%, and hide that fact. The battery graph's "0-100%" represents only that middle range in use. Plugging the Volt in also allows the car to keep the battery warm in the winter and cool in the summer, and can supplement the cabin preconditioning with wall power, saving more of the battery power for actual driving instead of heating the battery and the cabin with electricity you might more want to use for actually going somewhere.