Method and apparatus for controlling cooling and detecting abnormality in battery pack system

When an SOC difference between battery pack blocks (1a, 1b, 1c, 1d) exceeds a threshold, or a temperature difference between the battery pack blocks exceeds a threshold, a control section (4) changes cooling modes and cooling control maps for cooling fans (2a, 2b, 2c, 2d) of respective battery pack blocks to reduce variation in SOC and in temperature difference, thereby improving charging efficiency, and making degradation rates even, so that the life of the total battery pack system (10) is extended.