IEEE 485-2010 pdf free download – IEEE Recommended Practice for Sizing Lead-Acid Batteries for Stationary Applications.
4.2.4 Other considerations
The preceding lists of typical loads are not a full catalog of the dc loads at any one installation. The loads applied to the battery are normally categorized as constant power, constant resistance, or constant current. However, for sizing purposes, the loads are treated as constant power or constant current. The designer should review each system carefully to be sure all possible loads and their variations are included (see Annex B). If the loads are solely constant power loads, sizing as described in Annex E is appropriate and may simplify the sizing process.
4.3 Duty cycle diagram
A duty cycle diagram showing the total load at any time during the cycle is an aid in the analysis of the duty cycle. To prepare such a diagram, all loads (expressed in either current or power) expected during the cycle are tabulated along with their anticipated inception and shutdown times. The total time span of the duty cycle is determined by the requirements of the installation. 4.3.1 Defined loads Loads whose inception and shutdown times are known are plotted on the diagram as they would occur. If the inception time is known, but the shutdown time is indefinite, it should be assumed that the load will continue through the remainder of the duty cycle.
4.3.2 Random loads Loads that occur at random should be shown at the most critical time of the duty cycle in order to simulate the worst-case load on the battery. These may be noncontinuous or momentary loads as described in 4.2.2 and 4.2.3. To determine the most critical time, it is necessary to size the battery without the random load(s) and to identify the section of the duty cycle that controls battery size. Then the random load(s) should be superimposed on the end of that controlling section as shown in Figure 1 (see 6.3.4).
NOTE—This example is worked out in detail in Annex A. There it will be found that the first 120 min is the controlling portion of the duty cycle. Therefore, the random load is located on the duty cycle so that the random load ends at the end of the 120th min. This is indicated by the dashed lines. See Annex G for an additional discussion on treatment of random loads.
4.3.3 Duty cycle example
Figure 1 is a diagram of a duty cycle made中of the fllwing bhypothetical loads expressed in amperes:
L2 40 A for 3 h, continwous load
Ls 280 A for the Ist min, momentary load, actully 5 s starting current to load Ls
L460 A from the Ist min through the 120th min, noncontinuous load
Lg 100 A from the 30th min through the 120th min, noncontimuous load
L。80 A from the 30th min through the 60th min, noncontinuous load
Lr 80A for the last minute, momenary load, sctually a known sequence of: 40 A for the firstss, 80 A for the mext 10s. 30 A for the next 20 s
Lg 100 A for I min, random load (Actually this consists of four 25 A momentary loads that can occur at
any time within the duty cycle, Therefore, the assumption is that they all occur simulaneously,)
When the duty cycle includes constant power and constant curment loads, it is usually more convenient to convert the constant power load values to constant ceurent values for sizing calculations (see Annex B).IEEE 485 pdf download.