An apparatus for balancing a plurality of cells in a battery includes common bus having a connector for connecting to a common bus of another battery. The apparatus also includes a non-imaging optical system coupled to the housing that can output light to a surface and produce a scattered light component and a specular reflected light component. As an example, a protrusion may extend outward from a surface of the void, and the insert may define an indentation in a corresponding location and with a corresponding shape. The study specimen may have study regions formed thereon which are particularly suitable for study by atom probes, e.