NOVELTY - The apparatus has battery blocks (10) that are provided with battery cells (1) and endplates (7) that are provided at both ends. A base-panel (41) is provided to hold battery blocks that are provided in horizontal plane. The floor-panels (40) are mounted on top of battery block, and are provided with upper surfaces to hold other battery blocks. The battery block endplates are provided with upper attachment sections (52) and lower attachment sections to attach floor-panel or base panel which are provided on upper surfaces and lower surfaces of endplates respectively.    USE - Power source apparatus of power storage system used in vehicle (all claimed) such as electric vehicle e.g. electric auto-bike, plug-in hybrid vehicle and fuel-cell vehicle, for home and industrial power storage application. Can also be used in server computer and traffic signal, for wireless base station such as mobile phone base station, streetlight power source and solar cell.    ADVANTAGE - The endplates are attached to floor-panel or base-panel, so that the labor-saving for attachment operations can be attained and allocating space for nuts on the undersides of the floor-panels and base-panel can be avoided. The stack battery blocks are provided vertically with intervening floor-panels, and depending on the allotted space, the power source apparatus can be partitioned into two or three layers, so that the flexibility in the spatial disposition of battery blocks can be increased. The battery blocks can be attached in close proximity to each other via the floor-panels, so that the size of the battery block stacking structure can be reduced and the simplified battery block stacking structure can be attained. The interference between floor-panel attachment points can be avoided by laterally displacing the upper and lower level battery blocks, when battery block is stacked on the upper surface of another battery block with an intervening floor-panel. The attachment can be made without protrusion of bolt heads from the endplates, when a floor-panel is attached on top, so that the exterior size increase of the battery block stacking structure can be avoided. The stress applied to the high voltage bus-bars due to vibration and impact forces is reduced by the connecting hardware, so that the electrical connection between battery blocks with a margin of safety can be maintained and reliability of the battery block stacking structure can be increased.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a vehicle equipped with power source apparatus; and    (2) a power storage system equipped with power source apparatus.    DESCRIPTION OF DRAWING(S) - The drawing shows an exploded perspective view of the battery blocks.    Battery cells (1)    Endplates (7)    Battery blocks (10)    Floor-panels (40)    Base-panel (41)    Upper attachment sections (52)