This article delves into the crucial role of battery energy storage systems (BESS) in boosting renewable energy generation and its subsequent distribution. Large scale deployment of this technology is hampered by perceived financial risks and lack of secured financial models. This Note also discusses the fixed and variable revenue sources available to battery storage projects based on the benefits they offer to electricity. This article provides a detailed, engineer-oriented understanding of BESS, covering concepts, components, design considerations, applications, challenges, and future trends.