In this paper, we explore and describe the electromechanical coupling which results from eKEH conditioning circuits implementing a rectangular QV cycle, including but not limited to the charge pump and Bennet's doubler circuits. We present numerical and semi-analytical analyses describing the nonlinear relationship between the oscillating mass and the conditioning circuit. We believe this is a poorly understood facet of the device and, as we will portray, affects the potential harvested energy. An approach to determine the frequency shift due to the electromechanical coupling is presented and compared with novel experimental results. We provide some examples of bifurcation behavior and show that the only source of nonlinearity is in the coupling between the electrical and mechanical domains. This work continues from the electrical analysis presented in Part 1, providing a full insight into the complex behavior of the electromechanical coupling.