NOVELTY - The battery pack (100) comprises a housing (110) having a coupling recess (111), a peripheral portion around the coupling recess and cooling passages (112) extending in one direction normal to a top surface and a bottom surface of the housing within the peripheral portion, a battery cell (120) housed in the coupling recess, a heat screen on the housing, battery assemblies, each of which includes an electrode assembly (122), a current collector plate electrically coupled to the electrode assembly and a cap plate on the electrode assembly, and an insulating layer on inner walls of the housing.    USE - The battery pack is useful as a power supply system on a hybrid vehicle or an electric vehicle that is driven by the interaction of an engine with an electric motor.    ADVANTAGE - The battery pack is light-weight and economically manufactured with improved strength and electrical performance and without degradation, can be prevented from swelling arising from an increase in internal pressure during charging/discharging, and achieves optimum battery performance.    DETAILED DESCRIPTION - The battery pack (100) comprises a housing (110) having a coupling recess (111), a peripheral portion around the coupling recess and cooling passages (112) extending in one direction normal to a top surface and a bottom surface of the housing within the peripheral portion, a battery cell (120) housed in the coupling recess, a heat screen on the housing, battery assemblies, each of which includes an electrode assembly (122), a current collector plate electrically coupled to the electrode assembly and a cap plate on the electrode assembly, and an insulating layer on inner walls of the battery housing defining a corresponding one of the coupling recesses. The coupling recess comprises several coupling recesses, each of which houses the battery assemblies and an electrolyte. The heat screen has a planar surface covering a first array of the cooling passages, a first opening exposing the coupling recess, and second openings exposing a second array of the cooling passages and surrounding the first opening. An area of the cap plate is not less than an area of an opening of the coupling recess. The cap plate is flush with the heat screen and welded to the housing. The cooling passages are grouped at a first pitch, where the groups of the cooling passages are evenly spaced from each other by a second pitch greater than the first pitch. Each of the cooling passages has a circular, rectangular, pentagonal or hexagonal cross-section. The peripheral portion comprises a first peripheral portion and a second peripheral portion. The heat screen exposes a larger number of the cooling passages in the first peripheral portion than in the second peripheral portion.    DESCRIPTION OF DRAWING(S) - The figure shows a partially exploded perspective view of a battery pack.    Battery pack (100)    Battery housing (110)    Coupling recess (111)    Cooling passage (112)    Battery cells (120)    Electrode assembly. (122)