We present the application of our thermal battery system-level simulator [J. Electrochem Soc., 156, A442 (2009)] in novel multiplecell thermal analyses. Several model batteries are chosen to demonstrate the simulator's versatility and robustness in developing advanced thermal battery designs. The heat transfer phase-change model and supporting mass balance are modified to improve model consistency. Simulation results are presented from several case-studies covering different battery structures and operating conditions, including low and high current densities, different number of electro-active cells, various internal and external battery geometrical details, the use of salt buffers, external flanges, and inhomogeneous initial conditions in the battery stack. These results show the simulator to be a highly user-friendly and powerful tool for development of complex thermal batteries. Investigation of heat of reactions and joule heating effects unfold insights regarding dominant processes in multiple-cell batteries. Furthermore, these detailed analyses emphasize the need to track solidification dynamics at the sub-cell level and, at the same time, show that thermal battery design should include a significant ingredient of multiple-cell analysis. Altogether, this study presents a first-in-its-kind portable simulator with great flexibility and a capability for supporting the analysis and development of most thermal battery structures and designs. (C) 2014 The Electrochemical Society. All rights reserved.