Patent ID: 8907597

Claim:
A battery pack comprising: a first battery cell group comprising at least one high capacity battery cell; and a second battery cell group comprising at least one high output battery cell and being coupled in parallel to the first battery cell group, wherein the high output battery cell is configured to have a relatively greater current output value in comparison to the high capacity battery cell to output a greater current than the high capacity battery cell, the high capacity battery cell has a capacity to store a greater amount of electric energy compared to the high output battery cell, and wherein the battery pack further comprises: a battery management system configured to operate in one of operational modes comprising: a high capacity mode for outputting electric energy stored in the first battery cell group; a high output mode for outputting electric energy stored in the second battery cell group; an idle mode in which a charging and discharging operation is not performed when both a charge of the first battery cell group and a charge of the second battery cell group is greater than a reference value; and a mutual charge mode for charging the first battery ceil group or the second battery cell group when the charge of the first battery cell group or the charge of the second battery cell group is less than the reference value.