Battery energy storage systems (BESS) are the most versatile type of energy storage. With an increasing share of renewable energy, they could prove to be essential to provide the much needed flexibility. The MMCC-SSBC might be the most suitable converter for modern BESS. It is modular, and allows for an individualized treatment of the connected battery modules. The main objective of this thesis is to develop a tool which simulates the behavior of a MMCC-SSBC converter. This objective is fulfilled by the core deliverable of the thesis: a Matlab implementation of a dynamic model of the converter. As a secondary objective, this thesis aims to demonstrate the usefulness of this tool. It applies the tool to a specific use case, and analyzes three key characteristics based on the simulations: efficiency, power quality and reliability. This leads to some concise design guidelines, and continued operation under a battery short-circuit fault.