Lead-acid cell design

General Notes on Lead—Acid Cell Design... 

Flaving had over 150 years of technical development behind them, lead-acid batteries can be custom-tailored to specific applications, such as those requiring deep discharge cycles (e.g., where the batteries are used as the sole power source for electrical equipment) and for battery backup uses such as in large uninterruptible power supply systems in data centers. Moreover, lead-acid cells not only have low internal resistance but also experience no memory effect as do some more exotic cell designs, such as NiCads. This enables these cells to produce enormous currents and have a moderately long, predictable life.1... 

Lead-acid batteries were developed in 1859 by Plante. Scientists including Faure, Volk-mar, Brush, Gladstone, Tudor, Phillipart, and Woodward among others, contributed to improve Plante s cell and to create the lead-acid battery designs that are now available in the market. Lead-acid batteries use lead dioxide as cathode material, metallic lead as negative material, and a sulfuric acid solution as electrolyte. Different materials are used as separator, for example, microporous rubber, cellulose, polyvinyl chloride, polyethylene, and glass fiber. The cell reactions are... 

V design and comprises six lead-acid cells in a monobloc container. This battery is compatible with the vehicle electrical system that operates in the voltage range from about 12 to 14 V. Until around 1970, 6-V systems were also in use. In European trucks and buses on the other hand, it is common practice for two, 12-V batteries to be connected in series to achieve a nominal voltage of 24 V. 

The theoretical specific energy is never delivered in practical cells. To transform the lead—acid cell into a practical power source, several design requirements must he met. Figure 2.51 shows the construction of a conventional SLI battery [123]. 

Vents in use on valve-regulated lead-acid cells with immobilized electrolyte instead of normal venting plugs have to be designed in a way such that the user cannot open or remove them. 

Since the 1970s also maintenance-free valve-regulated lead-acid batteries have been in widespread use in the field of stationary applications. Sometimes they are called recombination cells or "sealed lead-acid cells". Their correct designation, however, is in accordance to DIN 40 729 valve-regulated lead-acid batteries ( VRLA batteries). 

Tiedemann, W. H., and Newman, J. (1979). Mathematical modeling of the lead-acid cell. In Battery Design and Optimization, S. Gross, Ed., pp. 23-38. The Electrochemical Society Softbound Proceedings Series, Princeton, NJ. 

Nguyen, T. V., White, R. E., and Gu, H. (1990). The effects of separator design on the discharge performance of a starved lead-acid cell. 

Of the conventional secondary systems, the nickel-iron and the vented pocket-type nickel-cadmium batteries are best with regard to cycle life and total lifetime. The nickel-hydrogen battery developed mainly for aerospace applications, has demonstrated very long cycle life under shallow depth of discharge. The lead-acid batteries do not match the performance of the best alkaline batteries. The pasted cells have the shortest life of the lead-acid cells the best cycle life is obtained with the tubular design, and the Plante design has the best lifetime. 

The equilibria of the electrode reactions are normally in the discharge direction since, thermodynamically, the discharged state is most stable. The rate of self-discharge [loss of capacity (charge) when no external load is applied] of the lead-acid cell is fairly rapid, hut it can be reduced significantly by incorporating certain design features. 

Lead-acid battery designs for many small portable, and some larger fixed applications, have often been referred to as sealed and/or maintenance free. This has been an accurate description to the extent that there was no need or opportunity to replace electrolyte. However, virtually no design included a true hermetic seal, and only a pressure release valve which limited inflow or outflow of gas to the cell. The valves released internal gasses at pressures ranging from a few tenths of an atmosphere to a few atmospheres. In addition, most lead-acid battery cases are molded of plastics, which are hydrogen permeable. 

Monobloc batteries, using the cylindrical cell, are produced with two to six cells interconnected in a single plastic container. These 4-, 6-, and 12-V batteries have performance characteristics similar to those of the single cell. The monobloc design is illustrated in Fig. 24.3. A newer type of small cylindrical lead-acid cell made within film electrodes has been introduced. This design has been characterized by Atwater et al. for use in portable electronic and communication applications. 

Thin flat prismatic sealed lead-acid cells have been designed for portable applications as they offer more flexibility in the design of the battery. They use space more efficiently than cylindrical cells, resulting in a higher volumetric energy density, and the slim design is adaptable to small-footprint equipment. " An exploded view of a typical flat cell is shown in Fig. 24.5. 

---