This report specifically focuses on battery energy storage in decentralized off-grid mini grids located in remote areas. It provides an overview of battery technologies used in mini grids globally, demand forecasts for various battery technologies, a comparison of characteristics of different batteries, an exploration of costs and trends in battery technologies, case studies, and recommendations. It also includes appendices that offer a broad overview of mechanical, electrochemical, and thermal storage, as well as performance optimization of lead acid batteries in mini grids.