In his written statement, the pilot of a motor glider reported that he climbed to 4,500 feet man sea level, shut down the engine, and soared for 15 minutes. When he attempted to restart the engine, the 'battery did not have enough power to operate the starter.' He landed in a field three miles east of the destination airport. A Federal Aviation Administration (FAA) Inspector who examined the wreckage reported that the motor glider was substantially damaged when it hit ditches.