A generator is controlled by a controller to generate power sufficient to a battery quickly in addition to power which is required by a wheel-drive motor for a while after a car is started and until a battery charging ratio becomes higher than a first predetermined ratio, between 80% and 100% for example. When the battery charging ratio becomes higher than the first predetermined ratio, the generator is controlled to generate a regulated power which is obtained by adding a constant power to the mean value of the power required by the wheel-drive motor to prevent the battery from generating gases due to overcharging. When the battery-charging ratio further increases and becomes higher than a second predetermined ratio, 120% for example, the generator is controlled to generate less power than the requirement of the wheel-drive-motor.