Islanded operations of electrical systems and low-voltage networks are presented in this work, with a special emphasis on battery energy storage systems, as well as the advantages and disadvantages of islanded low-voltage networks with integrated battery storage. The first chapter contains an introduction to the topic of the paper. The second chapter illustrates and describes low-voltage networks, their components, and the topological structure of low-voltage networks. The third chapter defines the technical requirements for the operation of low-voltage networks, such as rated voltage and frequency. The fourth chapter presents types of electrical energy battery storage systems, such as lead-acid batteries, lithium-ion batteries, nickel-cadmium batteries, nickel-metal hydride batteries, sodium-sulfur batteries, and vanadium redox flow batteries. Applications and the impact of battery storage systems in the network are also discussed. In the fifth chapter, technical requirements for islanded operations of low-voltage networks are outlined, along with the advantages and disadvantages of islanded operations. The sixth chapter provides an example of an islanded operation of a low-voltage network with a battery energy storage system, demonstrating the impact of photovoltaic power plants on the operation of low-voltage networks and the influence of energy storage systems on islanded operations. At the very end, there is a conclusion that includes a summary of the paper's chapters, battery storage systems, islanded operations of low-voltage networks, and a concluding analysis of an example of an islanded operation of a low-voltage network with a battery energy storage system.