Two methods are used to size stationary batteries, constant current and constant power. Constant current is used for applications such as generating stations, substations, and industrial control. Constant-power sizing is used almost exclusively for UPS system applications. Unlike constant-current loads, the current of a constant-power load (e.g., an inverter or dc motor) increases as the battery terminal voltage decreases during a discharge, so that P =E x I remains constant. Load profiles are not normally drawn for constant-power sizing since the load, once applied, remains the same throughout the battery discharge. A more detailed discussion of constant-power sizing is included in IEEE Standard 1184. Electric utility and industrial control-voltage windows generally use the standard cell end voltage but are sometimes limited by the minimum system-voltage limit. UPS applications can offer the largest voltage window, since the inverter input can be designed to accept a wide range of voltage without affecting the inverter