This paper explores the use of Li-Ion battery systems in off-grid applications. The study includes the development of a table that classifies and categorizes various off-grid battery systems based on their applications. A case study on photovoltaic battery off-grid systems is executed, providing practical insights into their application. User profiles of different systems are analyzed to draw an overview of their applications. The paper is finalized with a comparison of the case study with the simulation tool of Fraunhofer ISE called NRGISE. Overall, this research aims to contribute to the understanding and optimization of Li-Ion battery systems in off-grid applications. The paper is developed in the context of IEA PVPS task 18.