Battery pack with improved heat dissipation efficiency

A battery pack, comprising:

• a holder case;
• and
• a plurality of batteries disposed inside the holder case, the holder case comprising:
• a plurality of ribs disposed inside the holder case, each of the ribs comprising a column extending in a direction substantially parallel to a side surface of the holder case and a first fin extending in a first direction from the column, the column having a portion on which the first fin is formed, the column having another portion that further extends from the portion of the column along the direction substantially parallel to the side surface of the holder case, a first gap being formed between said another portions of two columns of the rib, the first fin not being formed on said another portion of the column, the first fin of one of the ribs directly contacting the first fin of another one of the ribs, each of the batteries being accommodated between the columns of the ribs, the column having a heat dissipation hole therein extending along the extension direction of the column, the portion of the column, on which the first fin is formed, having an undivided hollow shape with a hollow that forms the heat dissipation hole, said another portion of the column, on which the first fin is not formed, being divided into at least two sub-columns extending along the extension direction of the column, a second gap being formed between adjacent two sub-columns, the heat dissipation hole being surrounded by the sub-columns.