This guide discusses various battery systems so that the user can make informed decisions on selection@ installation design@ installation@ maintenance@ and testing of stationary standby batteries used in uninterruptible power supply (UPS) systems. This guide describes how the UPS battery charging and converter components can relate to the selection of the battery systems. Design requirements of the UPS components are beyond the scope of this document. Battery back-up systems for dc-output rectifiers are also beyond the scope of this document. While this document applies to all UPS systems@ it may be impractical to implement some of its guidance and recommendations with small@ self-contained systems@ such as products intended to back up individual personal computers.This guide divides the available technologies into the following three main categories: ?? Vented lead-acid batteries (VLA) ?? Valve-regulated lead acid (VRLA) ?? Ni-Cd batteries (Ni-Cd) For each category@ the technology and the design of the battery are described in order to facilitate user selection. The specific advantages for particular applications are also listed.