NOVELTY - The apparatus (1) has a temperature evaluation part (21) for evaluating temperature of a secondary battery (12) and determining whether heat retention is required. A charge/discharge control part (22) carries out a self-heating to the battery or charging of the battery when the battery needs to be heat-retained. The temperature evaluation part determines a retention battery. The charge/discharge control part uses the retention battery as a discharge battery such that electric power discharged from the discharge battery is charged at a charging battery using the retention battery.    USE - Apparatus for use in a parking lot of a large-scale facility e.g. airport facility and large-sized commercial establishment, for controlling temperature of a mobile-type/fixed-type secondary battery i.e. lithium ion battery, of an electric vehicle i.e. car. Can also be used for a residence for controlling temperature of a secondary battery of a hybrid vehicle.    ADVANTAGE - The secondary battery can be heat-retained using charge or discharge of the battery, so that performance decrement of the secondary battery can be suppressed, and the secondary battery can be heat-retained using the charge and discharge between the secondary batteries, thus achieving heat retention of the secondary batteries without being dependent on power receiving from a high order power network, and suppressing performance decrement of the secondary battery. The apparatus allows a charging battery determination part to determine the secondary battery by which amount of electrical storage is less than a predetermined value as the charging battery such that the discharge battery and the charging battery are determined based on the amount of electrical storage of the secondary battery, so that excess fall of the amount of electrical storage can be suppressed.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic block diagram of a battery control apparatus.'(Drawing includes non-English language text)'    Battery control apparatus (1)    Secondary battery (12)    Temperature evaluation part (21)    Charge/discharge control part (22)