A rechargeable battery pack having a housing, a plurality of cells located within the housing, a heat sink for dissipating heat from the plurality of cells, wherein the plurality of cells are encapsulated by the heat sink, and at least one elongated cooling channel to provide for active cooling, wherein the elongated cooling channel is within the housing and at least partially defined by the heat sink. A rechargeable battery pack having a housing, a plurality of cells located within the housing, wherein no single cell is completely surrounded by adjacent cells, a heat sink for dissipating heat from the plurality of cells, wherein the plurality of cells are encapsulated by the heat sink, and at least one elongated cooling channel to provide for active cooling, wherein the elongated cooling channel is located within the housing and is at least partially defined by the heat sink.