IEEE 1115:2014 pdf free download – IEEE Recommended Practice for Sizing Nickel-Cadmium Batteries for Stationary Applications
4.2.3 Noncontinuous loads
Noncontinuous loads are energized only during a portion of the duty cycle. These loads may switch on atany time within the duty cycle and may be on for a set length of time, be removed automatically or byoperator action, or continue to the end of the duty cycle. When several loads occur simultaneously withinthe same short period of time and a discrete sequence cannot be established, the load should be assumed tobe the sum of all loads occurring within that period. If a discrete sequence can be established, the load forthe period should be assumed to be the maximum load at any instant. If a load lasts for less than 1 s, it isnormally considered to last for a full second. Typical noncontinuous loads are as follows:
Noncontinuous loads for starting emergency generators，fire pumps，and other equipment powered byinternal-combustion engines represent a special sizing case for which the recommended procedures in thisdocument are not well suited.Annex D covers an industry-standard method for sizing nickel-cadmiumbatteries for engine-starting duties.
4.2.4 Other considerations
The lists of typical loads appearing in 4.2.2 and 4.2.3 are not a full catalog of the dc loads at any particularinstallation.Loads applied to the battery are normally typed as constant power，constant resistance,orconstant current. However, for sizing purposes, loads are treated as constant power or constant current. Thedesigner should review each system carefully to be sure all possible loads and their variations are included(see Annex B).
4.3 Duty cycle diagram
4.3.1 General
A duty cycle diagram showing total load at any time during the cycle is an aid in the analysis of the dutycycle.To prepare such a diagram, all loads, expressed as either power or current expected during the cycle,are tabulated along with their anticipated inception and shutdown times. The total time span of the dutycycle is determined by the requirements of the installation.
4.3.2 Known loads
Loads that have inception and shutdown times that are known are plotted on the duty cycle diagram as theywould occur. If the inception time is known but the shutdown time is indefinite, it should be assumed thatthe load will continue through the remainder of the duty cycle.
4.3.3 Random loads
Noncontinuous loads that occur at random should be shown at the most critical time of the duty cycle inorder to simulate the worst-case load on the battery.To determine the most critical time, it is necessary tosize the battery without the random load(s) and to identify the section of the duty cycle that controls batterysize.Then the random load(s) should be superimposed on the end of that controlling section, as shown inFigure 1 (see also 6.5.5).
5.2 Cell performance
All nickel-cadmium cells used in applications covered by this recommended practice are categorized bydifferent performance types, generally determined by plate thickness. Generally, high-rate cells (with thinplates) are used for loads requiring high-discharge currents of short duration. Low-rate cells (with thickplates) are used for loads of long duration.Medium-rate cells (with medium plate thickness) are used forlioads requiring combined performance. Any performance type can be utilized for any of these loadrequirements,but generally the economics will determine the correct type to be used. The differentperformance types are defined in IEC 60623 [B2].5
Cells designed for use in float operation are either vented or fitted with low-pressure valves. Hermeticallysealed cells of the type used in portable appliances are not suitable for operation with constant potentialchargers (see 6.4).