Lithium-ion battery prices have decreased over the years and are now becoming a viable option for data center UPS. This paper provides a brief overview of li-ion batteries in comparison to VRLA batteries for static UPS applications, including optimal chemistries and technologies. A 10-year total cost of ownership (TCO) analysis is provided showing li-ion is 39% less than VRLA despite their capital cost premium. A sensitivity analysis reveals the TCO drivers. Finally we discuss li-ion batteries for retrofit and new UPS applications and the effect of temperature on battery life, runtime, and cooling.