IEEE 1189-1997 pdf download IEEE Guide for Selection of Valve- Regulated Lead-Acid (VRLA) Batteries for Stationary Applications
1. Scope
This guide describes methods for selecting the appropriate type of valve-regulated, immobilized-electrolyterecombinant lead-acid battery for any of a variety of potential stationary float applications. Installation, maintenance.sizing, and consideration of battery types other than valve-regulated lead-acid batteries, are beyond the scope of thisguide. Design of the dc system and sizing of the dc battery charger(s) are also beyond the scope of this guide.
2.References
This guide shall be used in conjunction with the following publications:
IEEE Std 100-1992, The New IEEE Standard Dictionary of Electrical and Electronics Terms (ANSI).
IEEE Std 485-1983, IEEE Recommended Practice for Sizing Large Lead Storage Batteries for Generating Stationsand Substations (ANSI).
IEEE Std 1187-1996,1EEE Recommended Practice for Installation Design and Installation of Valve-Regulated LeadAcid Batteries for Stationary Applications.
IEEE Std 1188-1996.1EEE Recommended Practice for Maintenance, Testing, and Replacement of Valve-RegulatedLead-Acid (VRLA) Batteries for Stationary Applications.
3. Definitions
The following definitions apply specifically to this guide. For other definitions, see IEEE Std 100-1992
3.1 absorbed electrolyte: Electrolyte in a VRLA cell that has been immobilized in absorbent separators.
3.2 gelled electrolyte: Electrolyte in a VRLA cell that has been immobilized by the addition of a gelling agent.3.3 immobilized electrolyte: Electrolyte in a VRLA cell that is retained by using either gelled or absorbed electrolytetechnology.
3.4 oxygen recombination: The process by which oxygen is generated at the positive plates and ultimatelyrecombined with hydrogen ions at the negative plates and converted back to water. In this process, hydrogen gasformation and evolution are suppressed.(See annex A for more details.)
3.5 oxygen recombination efficiency: The amount of oxygen ultimately converted to water at the negative platesexpressed as a percentage of the total amount of oxygen produced at the positive plates:
O.converted to waler at the negative platesO2effX100total Oproduced at the positive plates3.6 valve-regulated lead-acid (VRLA) cell: A cell that is sealed with the exception of a valve that opens to thtatmosphere when the internal gas pressure in the cell exceeds atmospheric pressure by a preselected amount. VRLAcells provide a means for recombination of internally generated oxygen and the suppression of hydrogen gas evolutionto limit water consumption.
3.7 vented cell: A cell in which the products of electrolysis and evaporation are allowed to escape to the atmosphereas they are generated. These cells are commonly referred to as “flooded.”
3.8 VRLA cell: See: valve-regulated lead-acid (VRLA) cell.
4. Technology overview
4.1 Water loss
Water in a vented lead-acid cell is lost during overcharge by a process known as electrolysis. In this process, water isconverted to oxygen at the positive plates and to hydrogen at the negative plates. The oxygen and hydrogen gases areallowed to vent out of the cell into the atmosphere, resulting in the loss of water, In VRLA cells, the oxygerrecombination cycle limits the water loss.
4.2 Oxygen recombination
In a perfect water-to-oxygen-to-water cycle, all the oxygen produced at the positive plates on float or overchargewould be transported to the negative plates and converted back to water, with no water being lost from the cell. This isthe basis for VRLA cell technology (see annex A for more details).
4.3 Oxygen transport between positive and negative plates
The efficiency of the oxygen recombination cycle depends primarily on the ability to transport the oxygen generatedat the positive plates to the negative plates. In vented lead-acid cells, the transport process is impeded by the bulk liquicelectrolyte, and oxygen is liberated to the atmosphere. The migration of oxygen through liquid sulfuric acid electrolyteis approximately 10000 times slower than it is through air B1], (B2), (B3]. VRLA technology provides voids (gaspassages) between positive and negative plates through which oxygen transport is greatly enhanced.
IEEE 1189-1997 pdf download
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