Electro-Active Polymer (EAP) actuators inherently involve energy flow in multiple energy domains: mechanical, electrical, and at times, chemical and thermal. However, a complete predictive model explaining the behavior of EAPs has not yet been reported because of their complexity, particularly regarding the coupling phenomena between several energy domains. In this paper, we develop a model of EAPs suitable for dynamic simulations. The model uses bond graph methods as bond graphs are particularly appropriate for systems with multiple energy domains. Specifically, we develop a bond graph model for a conjugated polymer that behaves as an extensional electrolyte storage actuator using one cation- and one anion-exchanging polymer. The aims of this modeling are the following: to permit identification of known and as yet, unknown material properties of the elements in the system as a guide for future research by chemists and material scientists, to permit analytical evaluation of important questions such as what behavior determines the time constants and efficiency of the system, to allow design simulations which can provide guidance for best parameter choices for new devices, and to provide a modeling template for application to other sorts of EAP actuators such as IPMCs and gel-type.