ELECTRIC POWER STEERING DEVICE

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of using a cell of an auxiliary power source up to temperature near to heat resistant temperature.SOLUTION: An electric power steering device includes a motor 4 for generating steering assisting force, a main power source 7 for supplying electric power to the motor 4, an auxiliary power source 8 for connecting a plurality of cells in series and/or parallel, a charge-discharge circuit 9 for charging the auxiliary power source 8 based on the main power source 7 and selectively constituting a first output state of supplying the electric power to the motor 4 only by the main power source 7 and a second output state of supplying the electric power to the motor 4 from the main power source 7 and the auxiliary power source 8, a circuit 5 for driving the motor 4, temperature sensors 12 installed in the plurality of respective cells of the auxiliary power source and detecting the temperature of the respective cells, and a control circuit 6 for selecting the output state of the charge-discharge circuit 9 in response to the required steering assisting force and restricting charge-discharge on the auxiliary power source 8 when at least one of the temperatures detected by the respective temperature sensors 12 reaches a predetermined upper limit threshold value.