of charge discharge for the serial and parallel connection of battery packs of the three different group combinations are presented in fig5 a and 5b according to fig5 a and 5b the battery pack a u2014 a is much superior to the battery packs e u2014 e and a u2013 e in performance characteristic according to continuous charge discharge test the battery pack a u2013 e including one unit cell of group a having a good internal characteristic is similar in performance to the battery pack e u2014 e this means that the performance of the battery pack is largely dependent upon the unit cell of the inferior internal characteristic namely the battery pack configuration that includes a unit cell of good internal characteristic in combination with a unit cell of poor internal characteristic may have a deterioration of the performance due to the performance characteristic of the defective unit cell it is thus desirable to make a battery pack with unit cells of a similar internal characteristic in a same group i e a u2014 a b u2014 b c u2014 c d u2014 d or e u2014 e so as to prevent a deterioration of the performance due to the relatively inferior unit cell as described above the present invention provides a method of grouping unit cells for a battery pack configuration by measuring at least two parameters by an indirect.