A battery system includes a battery cell having a cylindrical battery cell housing and a housing support external to the battery cell housing. The housing support is formed of an electrical insulator layer contacting the cylindrical external surface of the battery cell housing, and a heat conductor formed of heat-conducting fibers overlying and contacting the electrical insulator layer and aligned generally parallel to the cylindrical axis of the battery cell housing. The heat-conducting fibers are made of high-thermal-conductivity graphite and have a sink end. A fiber-reinforced composite structural support layer is applied overlying the heat-conducting fibers to force the electrical insulator layer into contact with the battery cell housing without the presence of an adhesive between the electrical insulator and the battery cell housing. A thermal sink is in thermal contact with the sink ends of the plurality of heat-conducting fibers at a first end of the cylindrical battery cell housing. A structural base joined to the structural support layer is positioned at a second end of the cylindrical battery cell housing.