Lithium-ion batteries are coming into widespread use as a reliable backup power source for singlephase UPS systems in distributed network deployments, including 5G micro sites, edge data centers, server rooms, and data closets. With a higher power and energy density, faster recharge, and a longer lifespan and cycle life, lithiumion batteries are a more robust alternative to traditional lead acid batteries. The smaller size and lower weight of lithium-ion batteries makes them ideal for space-constrained deployments and easier to ship to remote areas, while greater tolerance to extreme temperature changes makes them a better choice for outdoor use. A Battery Management System (BMS) ensures safe operation, and helps to make lithium-ion batteries a maintenance-free solution. Over the 15-year life of a UPS system, lithium-ion batteries provide a considerable savings in Total Cost of Ownership (TCO) by reducing maintenance and operations costs, and eliminating the replacement costs of lead acid batteries.