NOVELTY - A battery pack (10) comprises a gas exhaust duct (60) forming a gas exhaust passage, which extends in an arrangement direction of battery modules (40) while being contiguous to a battery module unit (50) for exhausting the gas released in a case from the battery modules. The gas exhaust duct has a gas inlet (62) for leading the gas released in the case into the gas exhaust duct, and communicating with a gas emission hole (42) that is provided in each case to emit the gas; and air intake(s) (63) for taking in a cooling air flow (21).    USE - The battery pack is used for a vehicle (claimed), such as a hybrid vehicle, electric-powered vehicle, and fuel-cell vehicle. It is used as a power supply for driving a driving motor. The battery pack is for mounting under a seat in the center of the vehicle, under a rear trunk, or in an engine room in a vehicle front.    ADVANTAGE - The gas can be exhausted through the gas exhaust passage by not only the pressure of the gas itself, which is released from the cell but also an air flow that occurs by the cooling wind taken in through the air intakes of the gas exhaust duct. Thus, even when the quantity of the gas released from the cell is small, this gas can be exhausted, providing a battery pack with high reliability; and a vehicle with high reliability, endurance, gas mileage, and driving performance and sufficient power output even after long-term use, is achieved. The size of the gas exhaust duct becomes small as long as the gas exhaust duct can take in some cooling air flow through the air intake, and the projected area of the gas exhaust duct on the cooling air flow passage becomes relatively small. Thus, the increase in pressure loss of the cooling air flow due to the setting of the gas exhaust duct can be prevented. Since the gas exhaust duct is contiguous to, or more specifically, touches the battery module unit through the sealing portion along the arrangement direction, the gas exhaust duct also functions to support or hold each of the battery modules. Thus, even if vibration or movement of the vehicle is propagated to the battery module unit, the gas exhaust duct absorbs or attenuates the vibration, so that it is then possible to protect the battery module unit against vibration. The air flow is produced in the gas exhaust passage by taking in the part of the cooling air flow through the air intake. Thus, no additional passage, which provides the air flow in the gas exhaust passage, is required. Then the structure of the battery pack does not become complicated. Since the gas inlet is formed into the long hole shape, the gas inlet can compensate for some shift of the interval between the gas emission holes, and the gas can be exhausted out of the vehicle without causing the gas leakage to the cooling air flow passage. Quality and reliability of the battery pack can be thus increased. Because the gas inlet is enlarged only in the direction required for the compensation, the increase in pressure loss of the cooling air flow due to the setting of the gas exhaust duct can be prevented. The gas leakage to the cooling air flow passage can be avoided by the sealing portion, and the reliability of the battery pack is further increased.    DETAILED DESCRIPTION - A battery pack (10) comprises a battery module unit (50) having arranged battery modules (40), each having a cell (30), which is housed in a case and provided with a valve for releasing gas generated in the cell into an inside of the case; a cooling air flow passage, which is formed along an outer surface of the case of the battery module, and in which a cooling air flow (21) flows; and a gas exhaust duct (60) forming a gas exhaust passage, which extends in an arrangement direction of the battery modules while being contiguous to the battery module unit for exhausting the gas released in the case from the battery modules. The gas exhaust duct has a gas inlet (62) for leading the gas released in the case into the gas exhaust duct, and communicating with a gas emission hole (42) that is provided in each case to emit the gas; and air intake(s) (63) for taking in the cooling air flow. It has a sealing portion, which encircles a circumference of the gas inlet and encircles a circumference of the gas emission hole by touching the outer surface of the case. The cell employs a lithium-ion secondary cell.    DESCRIPTION OF DRAWING(S) - The drawing is a schematic view illustrating a flow of cooling wind or cooling air flow inside the battery pack.    Battery pack (10)    Cooling air flow (21)    Cell (30)    Battery modules (40)    Gas emission hole (42)    Battery module unit (50)    Gas exhaust duct (60)    Gas inlet (62)    Air intake (63)