As electronic devices become both ubiquitous and more energy efficient, powering them with energy harvested from, for example, piezoelectric materials has become a subject of much interest. The field does indeed show promise, as harvesting energy from smart materials has the potential to replace batteries completely in some low-power applications. This paper presents modeling of piezo-electret foam assembled in a multilayer stack configuration, with the required adhesives and conductors, as a multiple degree of freedom (MDOF) system. The benefits of using the foam over some piezo-ceramics include its high flexibility, its light weight, and its lead-free composition. This model predicts the mechanical and electromechanical response to base excitation for any number of layers of piezo-electret foam. Building upon previous work which modeled the piezo-electret stack as a single degree of freedom (SDOF) system, the MDOF model provides information concerning the response of internal stack layers. The MDOF model is validated against the experimentally determined mechanical and electrical responses of a 20-layer piezo-electret foam stack. Also, the internal stack dynamics at higher order vibration modes suggest that charge cancellation is a serious outcome of vibration at these modes that designers need to consider.