NOVELTY - The device (100) has battery block (3), cooling gaps (4), coupling element, and temperature equalizing plate (15). The equalizing plate includes attachment protrusion that protrudes from cooling gas downstream side of equalizing plate. A protrusion insertion portion is arranged at position of coupling element corresponding to attachment protrusion to insert attachment protrusion into protrusion insertion portion. The equalizing plate is attached to coupling element, when attachment protrusion of equalizing plate is inserted in protrusion insertion portion.    USE - Power supply device for vehicle such as electric vehicle and hybrid car. Can also be used in plug-in hybrid car and hybrid electric vehicle.    ADVANTAGE - Since the protrusion insertion portion is arranged at position of coupling element corresponding to attachment protrusion to insert attachment protrusion into protrusion insertion portion, and the equalizing plate is attached to coupling element when attachment protrusion of equalizing plate is inserted in protrusion insertion portion, the blowing cooling gas causing the free end of the temperature equalizing plate to fluster can be suppressed, and noise production can be suppressed. Since the battery blocks are held from the side surfaces by protrusion insertion portions, the battery blocks can be stably secured at increased mechanical strength. Since the elastic element arranged on the temperature equalizing plate comes in contact with the battery block, the vibration sound of the temperature equalizing plate when coming in contact with the battery block can be suppressed due to which low noise can be ensured. Since the area of the elastic element is changed in addition to the area of the temperature equalizing plate, the temperature difference among battery cells can be reduced. Since the temperature equalizing plate can be in contact with the battery block side tightly, an effect for closing the cooling gaps can be increased. Since the temperature equalizing plate is fastened only on the cooling gas inlet-side side surface of the both side surface of the battery block, the amount of cooling gas flows into cooling gaps can be effectively suppressed on the inlet side, due to which battery cells are cooled uniformly even the number of temperature equalizing plates is reduced. Since the temperature equalizing plate can be fastened to the bind bars with the attachment protrusions overlapping the bind bars, the opening areas of the cooling gaps are hardly affected by the attachment protrusions, due to which the temperature equalizing plate can be fastened to the battery block without affecting the function of the temperature equalizing plate. Since the protruding portions overlap one of the battery cells of the battery block when the temperature equalizing plate is fastened onto the side surface of the battery block, the protruding portion can be arranged at position that does not overlap battery cells due to which the protruding portion interferes with the flow of the cooling gas into the cooling gaps can be avoided, hence full use of the capabilities of the temperature equalizing plate can be made possible. Since the coupling element has two protrusion insertion portions at the symmetrical positions, the temperature equalizing plate can be fastened to the coupling members irrespective of orientation of the coupling members, due to which the power supply device can be assembled without concern for the orientation of the coupling elements, hence the orientation mistake can be eliminated, and the assembling efficiency can be improved. Since multiple battery blocks are arranged side by side in parallel to each other, two protrusion insertion portions of one battery block can contact two protrusion insertion portions of another adjacent battery block, due to which the contact stress can be distributed to two protrusion insertion portions, hence battery blocks can be more firmly connected between holding elements which makes the construction reliable.    DETAILED DESCRIPTION - The cooling gas is blown from side surface of battery block into cooling gaps to cool battery cells (1). The width of equalizing plate varies so that amounts of cooling gas flowing into cooling gaps are reduced as battery cells are located closer to cooling gas upstream side. The cooling gas upstream side of equalizing plate is fastened to battery block.    DESCRIPTION OF DRAWING(S) - The drawing shows a horizontal cross-sectional view of the battery system.    Battery cell (1)    Battery block (3)    Cooling gaps (4)    Temperature equalizing plate (15)    Power supply device (100)