R. Hauch 
2006 Toyota Prius Hatchback 4dr Hatchback (1.5L 4cyl gas/electric hybrid CVT)
Dead in Seven Days
 We drive this car around town mostly and  average about 45 MPG.  Several times a year we drive from Florida to Michigan and back.  The last trip our mileage average was 48.8. When the car sets for seven days or more, without being started, the battery goes dead.  Local dealer and Toyota advises this is normal. Their "fix" for this problem is having you disconnect the negative battery cable and then reconnecting it when you want to start the car. The battery is located beneath the floor in the cargo area.   