NOVELTY - The apparatus has a set of battery blocks made of a set of battery cells (1) e.g. rectangular battery cells, connected in multiple battery stacks (10) and an outer case holding the blocks. A block circuit board controls the battery cells of each battery stack. A set of electrical components (63) connected to the circuit board or the battery stack is arranged in a set of end-planes of each battery stack, where each component includes a fuse (63A) and a transistor (63B). A circuit board holder (61) retains the circuit board. An electrical component holder retains the components.    USE - On-board high-current power source apparatus for a motor i.e. electric motor, which drives an automobile e.g. hybrid car such as plug-in hybrid car, or electric vehicle. Can also be used for a hybrid electric vehicle.    ADVANTAGE - The apparatus has the board for controlling the cells of each stack and the electrical components arranged in the end-planes of each stack, where the electrical components are arranged in each block to eliminate the need for a special purpose electrical component case and avoid enlargement of the outer case. The apparatus separates heat-generating electronic components from block circuit board electronics, thus avoiding electrical component degradation due to heat generated by other electrical components, and hence improving reliability of the apparatus. The circuit board holder and the electrical component holder can be mounted in the end-planes of the stack in an orientation approximately parallel to the cells, where height and width of the block remain unchanged and only length of the stack is changed to retain the board and the electrical components, thus improving space utilization efficiency of the apparatus. The board can be arranged at an endplate at an end of the stack, and the electrical components are arranged at another endplate at another end of the stack, so that the electrical components are placed at both the endplates and sandwich the stack, thus maintaining mechanical strength of the apparatus while achieving a compact outline. The apparatus uses multiple flexible printed circuits used as voltage detection lines for electrical connection between a voltage detection circuit and a set of electrode terminals of each cell, thus eliminating labor-intensive wiring operation to connect the voltage detection lines such as lead-wires, to the stack and avoiding the need for realizing reliability and space reduction of a large number of lead-wires. The battery cells having rectangular shape can be efficiently arranged. The battery cells having cylindrical shape can retain an external case in a stable manner. The blocks have monitor and control functions to allow application-specific changes to the apparatus by simply changing number of blocks, thus simplifying design of the apparatus. The blocks can be replaced with a set of new battery blocks in the apparatus if malfunction occurs in the blocks, thus reducing maintenance and cost of the apparatus. The apparatus has a cooling plate that avoids equally cooling all the cells to regulate thermal energy absorbed from the cells and reduce temperature differences among the cells.    DESCRIPTION OF DRAWING(S) - The drawing shows a rear perspective view of a battery block.    Battery cells (1)    Battery stacks (10)    Circuit board holder (61)    Electrical components (63)    Fuse (63A)    Transistor (63B)