To provide a system for determining the degradation of a battery such as one having the discharging current varies constantly and being employed as the power supply of an electric vehicle, e.g. a golf car, by utilizing existing components without requiring a sensor, or the like, dedicated for degradation determination.

In an electric vehicle employing a battery as a power source, and a shunt motor controlled by a CPU as a drive source, where the armature coil and the field coil of the shunt motor are provided with a current sensor, respectively, degradation of the battery corresponding to the internal resistance of the battery is determined, based on the detected value of the current sensor.