Lead-acid SLI batteries

FIGURE 23.8 Maintenance-free lead-acid SLI battery. Courtesy of Delphi Energy Systems.)... 

FIGURE 23.17 Discharge curves of lead-acid SLI batteries, (a) At various hourly rates and 25°C. (b) At various high rates and -17.8°C. Battery rated at 70 Ah, 20-h rate at 25°C. 

FIGURE 23.19 Performance of lead-acid SLI batteries at various temperatures and discharge rates to 1.75-V per cell end voltage. 

FIGURE 23.20 Service life of lead-acid SLI battery to 1.75-V end voltage per cell. 

FIGURE 23.47 Charging characteristics of lead-acid SLI batteries at 25°C. 

Today, flooded lead acid batteries are used in SLI duty. Although installation of valve-regulated lead acid (VRLA) batteries in series-production vehicles began as early as the late 1980s [19 22], penetration of the SLI market by VRLA batteries has, so far, been quite limited. VRLA batteries are primarily used only in motorcycles, some military applications and, recently, in niche-markets such as luxury cars, taxis, and agricultural vehicles. 

Besides improvement of the utilisation of active materials (lead and lead dioxide), another crucial issue that has been in the focus of battery researchers and design engineers for many years now is the immobilisation of battery electrolyte via its absorption in the glass mat separator or by converting it into gel state. Thus, the valve-regulated lead—acid (VRLA) battery was invented which requires minimum or no maintenance and has found wide application. In the VRLAB construction, die active block in the SLI cell is higher and occupies the upper electrolyte reservoir space, thus increasing the capacity of the cell within the same volume. 

The introduction of the Tesla electric vehicle in 2007 with a 200 + mile range should set the stage for the transition to electric propulsion. The new cathode and anode systems also offer the potential to replace the present lead acid SLI (starting-lighting-ignition) battery on gasoline-powered vehicles. 

Another popular electrode design in the flat-plate construction, typically used in the lead-acid SLI and most larger storage batteries (Fig. 3.21c). This constraction also provides a large surface area for the electroehemical reaction. As with the other designs, the manufacturer can control the relationship between surface area and active material (for example, by controlling the plate thickness) to obtain the desired performance characteristics. 

In contrast to most other uses, lead-acid storage batteries have largely maintained, if not extended, their market position and range of applications in recent years. For the SLI market, especially, the lead-acid battery technology has several advantages over other alternative systems, in terms of both cost and performance (where lead s specific electrical and chemical properties are a crucial factor). The main influences here, as we have seen, have been technical changes which have improved battery performance, but economised on lead usage per battery. A further barrier to the introduction of any new, alternative SLI battery technolc is the widespread and weU-estab-lished infrastructure that already exists to produce and recycle lead-acid batteries. 

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

The case is the largest portion of the container. The case is divided into compartments which hold the cell elements. The cores normally have a mud-rest area used to collect shed soHds from the battery plates and supply support to the element. Typical materials of constmction for the battery container are polypropylene, polycarbonate, SAN, ABS, and to a much lesser extent, hard mbber. The material used in fabrication depends on the battery s appHcation. Typical material selections include a polypropylene—ethylene copolymer for SLI batteries polystyrene for stationary batteries polycarbonate for large, single ceU standby power batteries and ABS for certain sealed lead—acid batteries. 

Cost The cost of the battery is determined by the materials used in its fabrication and the manufacturing process. The manufacturer must be able to make a profit on the sale to the customer. The selling price must be in keeping with its perceived value (tradeoff of the ability of the user to pay the price and the performance of the battery). Alkaline primary Zn—MnOz is perceived to be the best value in the United States. However, in Europe and Japan the zinc chloride battery still has a significant market share. In developing countries, the lower cost Leclanche carbon—zinc is preferred. Likewise, lead acid batteries are preferred for automobile SLI over Ni—Cd with superior low-temperature performance but with a 10 times higher cost. 

Lead-acid batteries can be classified into three major types or categories, namely, automotive (SLI), stationary, and motive power (industrial). In addition, there are many special batteries that cannot be easily categorized as either of the above types. As these types of batteries are constructed with different materials and design to meet the requirements of their intended end uses, each requires a particular separator with specific material composition, mechanical design, and physical, chemical, and electrochemical properties that are tailored for the battery and its relevant specific uses. These batteries are generally available in flooded electrolyte or valve regulated (sealed) versions. In this section the types... 

The manufacture of secondary batteries based on aqueous electrolytes forms a major part of the world electrochemical industry. Of this sector, the lead-acid system (and in particular SLI power sources), as described in the last chapter, is by far the most important component, but secondary alkaline cells form a significant and distinct commercial market. They are more expensive, but are particularly suited for consumer products which have relatively low capacity requirements. They are also used where good low temperature characteristics, robustness and low maintenance are important, such as in aircraft applications. Until recently the secondary alkaline industry has been dominated by the cadmium-nickel oxide ( nickel-cadmium ) cell, but two new systems are making major inroads, and may eventually displace the cadmium-nickel oxide cell - at least in the sealed cell market. These are the so-called nickel-metal hydride cell and the rechargeable zinc-manganese dioxide cell. There are also a group of important but more specialized alkaline cell systems which are in use or are under further development for traction, submarine and other applications. 

Earlier collection schemes for all types of batteries have been established on a voluntary basis in several european countries like Switzerland, the Netherlands, Germany and Austria. They were usually the result of private or community (municipalities) initiatives. We will not address the issue of collecting spent lead-acid batteries of the SLI type as it is treated separately in this book. 

The lead/acid battery will remain the primary system for starting, lighting and ignition (SLI) applications. This does not pose a serious threat to the environment, since >85% of the batteries are presently being recycled. However, the sealed Pb/acid cells used in many consumer applications will probably go the way of... 

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