NOVELTY - The system has multiple battery packs (200) consecutively installed in a battery case (100). Multiple inner ducts (300) are provided in the battery packs and formed to enclose the respective battery packs in the battery case. A first group of apertures (320) is formed at a first set of ends of the inner ducts to be in communication with outside of the battery case. A second group of apertures (340) is formed at a second set of opposite ends of the inner ducts to be in communication with inside of the battery case, where each second aperture comprises different outlet resistance.    USE - Battery cooling system for a vehicle e.g. hybrid vehicle, electric vehicle or fuel cell vehicle (all claimed). Can also be used for a motor vehicle e.g. passenger automobile such as sports utility vehicle (SUV), bus and lorry, a watercraft such as boat and ship, an aircraft, a combustion vehicle, a plug-in hybrid electric vehicle, a hydrogen-powered vehicle and an alternative fuel vehicle.    ADVANTAGE - The system minimizes temperature deviation between the battery packs by individually providing ducts connected to the outside of the respective battery packs and allows outlet resistances of the respective ducts to be different from each other to allow cooling flow rates introduced into the respective battery packs to be the same for each battery pack, where the outlet resistances of the inner ducts are stepwise increased as the inner ducts get closer to the blower, so that the air flow rates flowing in the respective inner ducts are equalized and cooling rates of the battery packs are consistent, thus increasing entire cooling efficiency. The inner ducts are bent to allow flow rates of the respective inner ducts to operate smoothly and apply only some resistance to certain apertures so as to increase entire air flow rate while allowing air flow rates of the respective inner ducts to be same as each other.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a vehicle.    DESCRIPTION OF DRAWING(S) - The drawing shows a front view of a battery cooling system.    Battery case (100)    Battery packs (200)    Inner ducts (300)    Apertures (320, 340)    Blower (400)