A movable machine comprising: a vehicle body including a vehicle controller and a vehicle body frame; and a battery pack adapted to be removably mounted on the vehicle body, wherein the battery pack includes a rechargeable battery unit, a detector (33, 34) secured to the battery unit to detect the motion of the battery unit, the detector (33, 34) including an acceleration sensor, an angular velocity sensor, or both, a battery monitoring unit including a memory device and a processing device configured to record a history of motion information detected by the detector (33, 34) in the memory device, and a battery-side communication connector, and the movable machine includes an electric motor for propulsion of the movable machine, the electric motor being configured to use the battery unit of the battery pack as a power source or an auxiliary power source, and a vehicle body-side communication connector, wherein the battery-side communication connector is mechanically and electrically connectable to the vehicle body-side communication connector to enable communication between the battery monitoring unit and the vehicle controller to which the vehicle body-side communication connector is connected, and said battery-side communication connector is configured to output the motion information recorded in the memory device to the vehicle controller; and wherein the processing device or the vehicle controller diagnoses the state of the battery unit based on a history of motion information detected by the detector (33, 34) before mounting of the battery pack on the vehicle body of the movable machine, characterized in that the battery monitoring unit and the vehicle controller each include a diagnosis section, wherein the diagnosis section of the battery pack evaluates whether the battery pack has been dropped before mounting on the vehicle body depending on whether impact forces calculated based on the motion information history include an impact force larger than a predetermined threshold, and wherein the diagnosis section of the vehicle controller determines whether the use of the battery pack is acceptable based on the evaluation result obtained from the diagnosis section of the battery pack as to whether the battery pack has been dropped. a vehicle body including a vehicle controller and a vehicle body frame; and a battery pack adapted to be removably mounted on the vehicle body, wherein the battery pack includes a rechargeable battery unit, a detector (33, 34) secured to the battery unit to detect the motion of the battery unit, the detector (33, 34) including an acceleration sensor, an angular velocity sensor, or both, a battery monitoring unit including a memory device and a processing device configured to record a history of motion information detected by the detector (33, 34) in the memory device, and a battery-side communication connector, and a rechargeable battery unit, a detector (33, 34) secured to the battery unit to detect the motion of the battery unit, the detector (33, 34) including an acceleration sensor, an angular velocity sensor, or both, a battery monitoring unit including a memory device and a processing device configured to record a history of motion information detected by the detector (33, 34) in the memory device, and a battery-side communication connector, and the movable machine includes an electric motor for propulsion of the movable machine, the electric motor being configured to use the battery unit of the battery pack as a power source or an auxiliary power source, and a vehicle body-side communication connector, an electric motor for propulsion of the movable machine, the electric motor being configured to use the battery unit of the battery pack as a power source or an auxiliary power source, and a vehicle body-side communication connector, wherein the battery-side communication connector is mechanically and electrically connectable to the vehicle body-side communication connector to enable communication between the battery monitoring unit and the vehicle controller to which the vehicle body-side communication connector is connected, and said battery-side communication connector is configured to output the motion information recorded in the memory device to the vehicle controller; and wherein the processing device or the vehicle controller diagnoses the state of the battery unit based on a history of motion information detected by the detector (33, 34) before mounting of the battery pack on the vehicle body of the movable machine, characterized in that the battery monitoring unit and the vehicle controller each include a diagnosis section, wherein the diagnosis section of the battery pack evaluates whether the battery pack has been dropped before mounting on the vehicle body depending on whether impact forces calculated based on the motion information history include an impact force larger than a predetermined threshold, and wherein the diagnosis section of the vehicle controller determines whether the use of the battery pack is acceptable based on the evaluation result obtained from the diagnosis section of the battery pack as to whether the battery pack has been dropped.