NOVELTY - The device has a main portion which is provided with rectangular parallelepiped battery case (10). A pair of opposing walls (12) and a pair of end surface walls (13) of case are provided around the tetragonal bottom surface plate. The electric condenser (2) is connected in parallel with the lead battery (1). The regenerative braking power storage capacity of condenser is greater than the regenerative braking power storage capacity of lead battery. The thermal radiation plate (22) is provided in the exterior case (20) and is thermally bonded to the opposite walls of lead battery.    USE - Power supply device for vehicle with regenerative braking function.    ADVANTAGE - Since the thermal radiation plate is thermally bonded to opposite walls of lead battery, the deterioration of the lead battery due to excessive current of battery can be prevented. Hence the service lifetime of the lead battery can be extended. The device can prevent the abnormal temperature rise of an electric condenser, without using complicated cooling mechanisms such as cooling fan. The regenerative braking power storage capacity of condenser is greater than the lead battery, so that the electrical storage amount of the condenser can be increased while decreasing the electrical storage amount of lead battery. The charging current of the lead battery during regenerative braking is increased, so that large amount of heat can be emitted to the outside. The abnormal rise in the temperature of device can be suppressed. The thermal radiation plate is thermally bonded to the opposite walls of lead battery, such that the heat of the electric condenser can be radiated efficiently. The heat of an electric condenser can be thermally radiated with good balance in the electrolyte solution. The power supply device has a rated voltage of a nickel-hydrogen battery, and the equal rated voltage of one cell of a lead battery, so that the number of objects connecting the nickel-hydrogen battery in series can be adjusted. The rated voltage of an electric condenser can be made equal to the rated voltage of a lead battery, so that the nickel-hydrogen battery and an electric condenser can be connected in parallel directly, without providing voltage adjustment circuits. The can lead battery and an electric condenser can be charged and discharged efficiently with good balance. The capacitance of the power supply device can be increased.    DESCRIPTION OF DRAWING(S) - The drawing shows a top view of the power supply device.    Lead battery (1)    Electric condenser (2)    Battery case (10)    Opposing walls (12)    End surface walls (13)    Battery case (20)    Thermal radiation plate (22)