A battery pack apparatus including a battery pack having a plurality of rechargeable batteries arranged in parallel, with a cooling medium passage interposed therebetween, a cooling medium feeding device for feeding a cooling medium through the cooling medium passages, and a control section for controlling the charge and discharge of the battery pack. In this configuration, the battery pack apparatus is divided into a first unit including the battery pack and the cooling medium feeding device and a second unit having the control section accommodated in a case. The battery pack of the first unit is connected with the control section of the second unit by means of a harness or metallic connecting member.