Automotive batteries

Despite the popular association of arsenic to poisons, the element has found several uses. Alloys are made with Pb and to a lesser extent with Cu. The addition of small quantities of As improves the properties of Pb/Sb for storage batteries. Automotive body solder is Pb (92%), Sb (5.0%), Sn (2.5%), and As (0.5%). The ni-V semiconductors especially GaAs and InAs are very important in the fabrication of LEDs, tunnel diodes, infrared emitters, laser windows, and Hall-effect devices. It also found use in agricultme as herbicide and pest controls but now is very restricted because of environmental... 

Small nickel/cadmium and lead-acid batteries generally experience the same fate. With some exceptions, the larger rechargeable batteries, automotive batteries in particular, are returned to the vendors to a large extent for subsequent recycling by the manufacturers, or for processing by scrap metal operators for recovery of their intrinsic metal values. 

Thin-film capacitors for computer chips Solid polymer electrolytes for batteries Automotive engine parts and fuel tanks Impellers and blades Oxygen and gas barriers Food packaging... 

Rea.ctivity ofLea.d—Ca.lcium Alloys. Precise control of the calcium content is required to control the grain stmcture, corrosion resistance, and mechanical properties of lead—calcium alloys. Calcium reacts readily with air and other elements such as antimony, arsenic, and sulfur to produce oxides or intermetaUic compounds (see Calciumand calciumalloys). In these reactions, calcium is lost and suspended soHds reduce fluidity and castibiUty. The very thin grids that are required for automotive batteries are difficult to cast from lead—calcium alloys. 

Wrought lead—calcium—tin alloys contain more tin, have higher mechanical strength, exhibit greater stabiUty, and are more creep resistant than the cast alloys. RoUed lead—calcium—tin alloy strip is used to produce automotive battery grids in a continuous process (13). Table 5 Hsts the mechanical properties of roUed lead—calcium—tin alloys, compared with lead—copper and roUed lead—antimony (6 wt %) alloys. 

As with SMC, appHcations are limited to high volume because of the capital investment in equipment and tooling. Thermoset compression molders require additional heating and material Handling equipment to adapt their process to thermoplastic sheet fabrication. AppHcations include automotive bumper beams, load floors, radiator supports, battery trays, and package shelves. Chair sheUs, military containers, material Handling pallets, trays, and concrete foaming pans are also produced. 

Two more recent appHcations for amorphous siHcas are expected to grow to large volumes. Precipitated siHcas are used ia the manufacture of separator sheets placed between cells ia automotive batteries. Their function is to provide a controlled path for the migration of conductive ions as a result of the porosity of the siHca particles. Additionally, both precipitated siHcas and aerogels are being developed for use ia low temperature iasulation, where the low thermal conductivity of the dry siHca powders makes them useful ia consumer products such as refrigerators (83). 

Because the nickel—iron cell system has a low cell voltage and high cost compared to those of the lead—acid battery, lead—acid became the dorninant automotive and industrial battery system except for heavy-duty appHcations. Renewed interest in the nickel—iron and nickel—cadmium systems, for electric vehicles started in the mid-1980s using other cell geometries. 

In Figure 1, the cutaway view of the automotive battery shows the components used in its constmction. An industrial motive power battery, shown in Figure 2 (2), is the type used for lift tmcks, trains, and mine haulage. Both types of batteries have the standard free electrolyte systems and operate only in the vertical position. Although a tubular positive lead—acid battery is shown for industrial appHcations, the dat plate battery constmction (Fig. 1) is also used in a comparable size. 

Fig. 1. Cutaway view of an automotive SLI lead—acid battery container and cell element.

World production of lead—acid batteries in 1988, excluding the Eastern European central economy countries, has been estimated at 9.45 biUion. The automotive market was 6743 million or 211.6 million units. Industrial battery sales were 2082 million and consumer battery sales were 454 million. Motorcycle batteries accounted for an additional 170 million or 25 million units. Most batteries are produced in the United States, Western Europe, and Japan, but smaller numbers are produced worldwide. The breakdown in sales for the three production areas foUows. Automotive battery sales were 2304 million in the United States, 1805 in Western Europe, and 945 million in Japan. Industrial battery sales were 525 million in the United States, 993 million in Western Europe, and 266 million in Japan. Consumer battery sales were 104 million in the United States, 226 million in Japan, and 82 million in Western Europe. More than half of all motorcycle batteries are produced in Japan and Taiwan (1). 

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. 

Typical dimensions for the /5-alumina electrolyte tube are 380 mm long, with an outer diameter of 28 mm, and a wall thickness of 1.5 mm. A typical battery for automotive power might contain 980 of such cells (20 modules each of 49 cells) and have an open-circuit voltage of lOOV. Capacity exceeds. 50 kWh. The cells operate at an optimum temperature of 300-350°C (to ensure that the sodium polysulfides remain molten and that the /5-alumina solid electrolyte has an adequate Na" " ion conductivity). This means that the cells must be thermally insulated to reduce wasteful loss of heat atjd to maintain the electrodes molten even when not in operation. Such a system is about one-fifth of the weight of an equivalent lead-acid traction battery and has a similar life ( 1000 cycles). 

Research, development and entrepreneurial activities are peiwasive, fueled by ever-growing demands for lighter, smaller and more powerful batteries with even more reliability and extended shelf life for industrial, automotive, military, business, medical, and home uses. Mobile communications, coiuput-... 

M. Eskra, P. Eidler, R. Miles, Zinc-bromine battery development for electric vehicle applications, Proc. 24 h hit. Symp. Automotive technology and Automation, Florence, 1991. 

Reprinted from W. Bohnstedt, Automotive lead/acid battery separators a global overview, J. Power Sources, 1996, 59, 45-50, with kind permission from Elsevier Science S.A., Lausanne. 

---