Off-grid alternative energy homes typically rely on battery banks to store surplus power for use when the various generation devices aren't working at their strongest (i.e. solar panels in cloudy weather or at night, windmills when it isn't windy, micro-hydro when the water flow has dried up, etc). The battery most often used in these installations is called a deep-cycle battery, and is substantially different than the battery you would expect to find in an automobile.
