Maintenance lead-acid batteries

Recent work has shown that two parameters, namely low electrical resistance and low senarator thickness, have a profound effect on cold cranking performance of low-maintenance calcium-lead alloy automotive batteries. Figure 18.20 and 18.21 show the beneficial effect of decreasing the electrical resistance of the separator on the cell voltage in tests run at — 18°C and —30°C on low-maintenance lead-acid batteries. 

Low-maintenance lead-acid batteries usually feature a special calcium-lead grid instead of the lead-antimony alloy used in conventional lead-acid batteries such as the traction battery. The elimination of antimony and other metallic impurities from the alloy increases the ability of the battery to retain its charge when not in use and gives the battery a shelf life of about five times as long as when the conventional lead-antimony alloy is used. Even at elevated temperatures the shelf life with calcium-lead alloys exceeds that obtained with conventional alloy. 

The charging of low maintenance lead-acid batteries has been discussed in a book published by Gate Energy Products (see Bibliography). 

Historically, subsequent to exploratory studies on lead-acid systems by Daniel, Grove and Sindesten, practical lead-acid batteries began with the research and inventions of Raymond Gaston Plante in France as early as 1859 and, even today, lead-acid battery remains the most successful battery system ever developed. There are three types of lead-acid batteries in common use (1) batteries with flooded or excess electrolyte, (2) low-maintenance lead-acid batteries with a large excess of electrolyte and (3) batteries with immobilised electrolyte and a pressure-sensitive valve, usually referred to as valve-regulated lead-acid (VRLA) or sealed lead-acid (SLA) batteries [3]. 

Selenium acts as a grain refiner in lead antimony alloys (114,115). The addition of 0.02% Se to a 2.5% antimonial lead alloy yields a sound casting having a fine-grain stmcture. Battery grids produced from this alloy permit the manufacture of low maintenance and maintenance-free lead—acid batteries with an insignificant loss of electrolyte and good performance stability. 

In the 1990s, the use of batteries in electric vehicles and for load leveling is being revived partly for environmental reasons and partly because of scarce energy resources. Improvements in battery performance and life, fewer maintenance requirements, and automatic control systems are making these appHcations feasible. Research and development is ongoing all over the world to develop improved lead—acid batteries as weU as other systems to meet these needs. 

Whereas automotive batteries have the majority of the market, other types of lead—acid batteries, such as sealed and small maintenance-free varieties, are making inroads into various appHcations. The automotive battery s operating environment has changed substantially in the last 10 years. Underhood temperature has risen and electrical loads have increased. This trend is expected to continue as car manufacturers reevaluate thek design strategies and objectives. Battery design is changing to meet these needs. 

J. R. Pierson, C. E. Weinlein, and C. E. Wright, "Determination of Acceptable Contaminant Ion Concentration Levels in a Truly Maintenance-Free Lead—Acid Battery," in D. H. Collins, ed.. Power Sources 5-1974 Pergamon, London and New York, 1975. 

Vehicle maintenance shops Heavy-metal paints Ignitable materials Used lead-acid batteries Spent solvents... 

Finally, a sine qua non is acceptable cost. The factors to be considered are the initial price of the battery, the operational life of the battery, and the associated maintenance costs. Lead-acid batteries are eminently suitable for medium- and large-scale energy-storage operations because they offer an acceptable combination of performance parameters at a cost which is substantially below that of alternative systems. 

European Advanced Lead-Acid Battery Consortium, Brite/Euram Project BE97-4085, The development of improved lead-acid batteries for electric vehicle service which are maintenance-free and fully recyclable. Final Report 1 January 1998 to 31 August 2001, Appendix IV, p. 50, Advanced Lead-Acid Battery Consortium, Research Triangle Park, NC, USA, 2001. 

Traditionally, flooded lead-acid batteries have been the technology of choice for use in RAPS systems. During the last 10 years, however, there has been a considerable shift towards VRLA batteries. The main driver for this change is the low maintenance requirement of the latter technology. This and other important issues are discussed in the following sections. 

In recent years there has been a tendency to prefer Pb cells instead of NiCd cells. This has been due to the development of what has become known as maintenance free or sealed type lead-acid batteries. The basic concept is one of retaining the gases evolved during the charging process and to allow the oxygen to recombine as float charging takes place, see Reference 4. If the operating and ambient conditions are not subject to excessive variation then the concept is satisfactory in practice and the life expectancy of the battery can be as much as 10 years. 

In the first half of the twentieth century, lead alloys with high antimony content were used for the manufacture of the plate grids for lead—acid batteries. These batteries lost water during operation and hence they needed maintenance. Significant efforts of battery seientists and technologists in the twentieth century were focused on resolving the water loss problem. 

A semiconductor mechanism was proposed for the electrocatalytic action of tin on the oxidation of PbO to PbO and Pb02. Tin has substituted antimony as an additive to the alloys for lead—acid battery grids. It is added in considerably lower concentrations than Sb and in combination with calcium which improves the mechanical properties of the alloys. Thus the interface problem of lead—calcium grids was resolved and the way was open for the manufacture of maintenance-free wet-charged batteries. 

As evident from Fig. 4.41 in Chapter 4 of this book, when Pb—Ca—Sn positive grids contain up to 1.8 wt% Sn, no tet-PbO layer forms in the corrosion layer. That is why the positive grids for all types of maintenance-free valve-regulated lead—acid batteries are cast from lead alloys with 0.05—0.07 wt% Ca and 1.5—1.7 wt% Sn content. 

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