Abstract: A battery condition monitoring system which may be employed in an electric vehicle is disclosed. This system determines a terminal voltage of a battery under discharge of a given current and a consumption of electric energy stored in the battery and calculates a rate of change in terminal voltage of the battery relative to change in consumption of electric energy. When a difference between the rate of change in terminal voltage of the battery and a reference rate representing a rate of change in terminal voltage of a normal battery relative to change in consumption of electric energy is greater than a given value, the system determines that memory effect is occurring in the battery.