Battery pack with improved heat dissipation efficiency

A battery pack comprising: a holder case; and a plurality of batteries arranged within the holder case with their respective first axes aligned substantially parallel to each other. The holder case comprises a plurality of columnar structures, each said columnar structure being located intermediate at least two said batteries and aligned substantially parallel to the said first axes of the said batteries. Each columnar structure serves to define at least one heat dissipation channel between batteries adjacent thereto.