Figure 15. Diagram of a duty cycle

^L2 ^L5 ^L4 ^L3 ^L1 ^L6 ^L7 ^L7 1 30 60 90 120 150 179 180 320 280 240 200 180 120 80 40 1 Minutes Min Lead-Acid Storage Batteries DOE-HDBK-1084-95 SIZING AND SELECTION Rev. 0 Page 27 Batteries SIZING AND SELECTION Sizing and selection of lead-acid batteries should be performed according to ANSI/IEEE Std 485, IEEE Recommended Practice for Sizing Large Lead Storage Batteries for Generating Stations and Substations. As described earlier, the duty cycle is the most important criterion in battery sizing and selection. ANSI/IEEE Std 485 contains directions as well as a sample exercise for determining the duty cycle. A simple duty cycle diagram is shown in Figure 15. Each of the loads (designated by L ) requires a certain amperage for a specified time and 1-6 duration. In the example duty cycle, a randomly occurring load (L ) is assumed to occur in 7 the 120th minute. The placement of randomly occurring loads in the duty cycle is also covered in ANSI/IEEE Std 485. Figure 15. Diagram of a duty cycle.