A battery system includes a plurality of non-cylindrical shaped battery cells arranged on, and physically affixed to, a flexible printed circuit board (PCB). The PCB may include a bend axis that facilitates folding of the flexible PCB to form an upper portion of the flexible PCB and a lower portion of the flexible PCB. A central stiffener may be positioned between the upper portion and the lower portion of the flexible PCB using an adhesive foam tape to form a battery assembly. The battery system may include a flexible housing with an internal cavity that receives the battery assembly. The central stiffener, and the adhesive foam tape, may provide a degree of rigidity and/or absorption to the PCB to reduce localized deformation of the PCB when the battery system experiences shock forces and to prevent damage to components of the battery assembly. The stiffener may be formed from non-metallic material. In addition, the stiffener may include a laminate layer with a plurality of fibers embedded within the laminate layer. The plurality of fibers may be oriented at approximately a 45 degree angle with a lower edge of the laminate layer.