A battery system for providing electric power to a vehicle includes an assembly having battery cells. The battery system also includes a shear wall that is arranged along a lateral side of the assembly to provide structural support. The shear wall is two-part, including a first element and a second element, both of which may be formed from sheet metal and welded together. The first element has a first flange extending away from the lateral side of the assembly, and the second element has a second flange. The first flange and the second flange are layered together to form an interface. The flanges are welded together at the interface, proximal to the assembly, to form a resulting flange that is thicker than either individual flange and that may be mounted to a frame member. The battery system may also include another shear wall on the opposite lateral side.