How it works...

The Normal Map was calculated from the grey values on the Heightmap, where the lighter tones were interpreted as recesses (applied to the top of the battery), and the darker tones as bulges (applied to the bottom). Since the desired output was actually the opposite, it was necessary to adjust the Normal Map to a negative value (-0.35). Another possible solution to the issue would have been to redraw the Heightmap and switch the colors for the white and black circles.