A method for controlling charge or discharge of a battery in a battery system including a DC converter down-converting an input voltage thereof and outputting an output, a battery connected to an output terminal of the DC converter, and an electric load connected to the output terminal of the DC converter and supplied with electric power from at least one of the DC converter and the battery, may include measuring a temperature of the battery, first controlling, by a controller, an output of the DC converter so that a charging current supplied to the battery from the DC converter becomes a preset maximum value, when the temperature of the battery is lower than a first predetermined temperature, and second controlling, by the controller, the output of the DC converter such that a current of the battery is substantially equal to zero, when the temperature of the battery is higher than a second predetermined temperature which is higher than the first predetermined temperature.