Systems, devices, and techniques for active thermal control of energy storage units are described. In some embodiments, an unmanned aerial vehicle (UAV) includes a battery pack. The battery pack includes a plurality of battery cells and an enclosure coupled with the plurality of battery cells to physically retain the plurality of battery cells in an arrangement. The arrangement defines a void space between the plurality of battery cells. The UAV also includes a cooling system configured to cool the battery cells. The cooling system includes a source of forced convection fluidically coupled with the battery pack to drive a cooling fluid through the void space. The cooling system also includes a cooling controller electrically coupled with the source of forced convection to controllably activate the source of forced convection.