1. A vehicle communication system in which an in-vehicle battery is charged from an external power supply connected thereto via an electric power line and external communication using the electric power line as a communication conduit is enabled, the vehicle communication system characterized in that: through external communication performed during charging, the vehicle communication system transmits vehicle information and receives control parameter information that is set in accordance with one or more characteristics of a geographical area where the charging is performed and the transmitted vehicle information, and a control parameter of a vehicle is set in accordance with the received control parameter information.