Lithium-ion batteries offer several advantages over traditional lead acid batteries. Despite the benefits, the use of lithium-ion batteries in uninterruptable power supplies (UPSs or battery backups) is relatively new with valve-regulated lead acid batteries still the dominant energy storage technology used today. This will likely change as Li-ion costs continue to decrease, the benefits become more widely known, and manufacturers make their UPSs compatible. This paper serves to answer common questions about Li-ion batteries and their use in UPSs.