Lead-acid traction battery

FIGURE 1.18 Weight component of SLI and traction lead-acid batteries. 

The historical development of the separator and of the lead-acid storage battery are inseparably tied together. When referring to lead-acid batteries today one primarily thinks of starter batteries or forklift traction batteries, but the original applications were quite different. 

The world market for batteries of all types now exceeds 100 billion. Over half of this sum is accounted for by lead-acid batteries - mainly for vehicle starting, lighting and ignition (SL1), and industrial use including traction and standby power, with about one-third being devoted to primary cells and the remainder to alkaline rechargeable and specialist batteries. 

By far the largest sector of the battery industry worldwide is based on the lead-acid aqueous cell whose dominance is due to a combination of low cost, versatility and the excellent reversibility of the electrochemical system, Lead-acid cells have extensive use both as portable power sources for vehicle service and traction, and in stationary applications ranging from small emergency supplies to load levelling systems. In terms of sales, the lead-acid battery occupies over 50% of the entire primary and secondary market, with an estimated value of 100 billion per annum before retail mark-up. 

Over the past few years a number of studies have been made of the use of lead-acid batteries for load levelling. The service required is very similar to that of traction batteries except that energy density is less important than cycle efficiency. 

Different types of lead-acid batteries have been developed as energy sources for many power applications, like traction and backup or standby power systems. The flooded lead-acid batteries have an excess or flooded electrolyte and they were the largest used at the beginning of the last century for many applications. Valve-regulated lead-acid (VRLA) batteries were developed as an alternative to the flooded lead-acid batteries, in order to maintain levels of distilled water and prevent drying of cells, which means safe operation for battery packs in electric... 

The classical scheme for the manufacture of flat pasted plates for automotive, traction and stationary lead-acid batteries is shown in Fig. 3.1. There is no difference between the technology of plate manufacture for conventional (flooded) and valve-regulated (VRLA) lead acid batteries. The two versions do differ, however, in the method of separation of the plates, the quantity and type (hquid or gel) of electrolyte, and in the design of the battery itself. 

Lead acid batteries have been used for more than 130 years in many different applications including automotive and various traction duties and also telecommunication systems and uninterruptible power supphes (UPS). The last two groups constitute the major part of the so-called stationary battery sector, and the lead-acid battery has proved to be a very reliable system for these appUcations. 

Sonnenschein was the first company to introduce gel battery technology to the market successfully. They started in 1958 with rather small batteries for flashlights. Since that time, this technology has steadily replaced the conventional, flooded lead-acid battery in various applications [38,71,72]. Phosphoric acid addition for cycling was first introduced in 1965. Larger gel batteries with tubular positive plates were developed for stationary applications in 1978. More recently, gel batteries have been produced for starter and traction applications, and thick, flat positive plates were added for telecommunications applications. 

Lead is used in batteries, inorganic chemicals, pipes, solders, electric wires, etc., but batteries accounted for 72% of the total usage of lead in 1997. Therefore it can be said that batteries play an important role in the recycling of lead. Lead-acid batteries are classified into motor vehicle batteries (for automobiles and motorcycles), industrial batteries (stationary batteries, traction batteries, etc.), small-size sealed batteries (for UPS and consumer products). Table 2.1 shows their shipments. 

As evident from these data, the electrochemically and chemically active components in a lead—acid battery account for about two-thirds of the total battery weight. Mass-produced SLI batteries have typical specific energy values of 34—40 Wh kg , whereas traction EV batteries have a specific energy of between 28 and 34 Wh kg ... 

The classical technological scheme for the manufacture of flat-plate lead—acid batteries is presented in Fig. 2.52. This technological process is basically used for the production of SLI, traction and stationary batteries. The process involves the following main production stages ... 

Table 15.1 presents the value ranges for the specific capacity per kg active mass (weight coefficients (jS) per Ah for the basic types of commercial lead—acid batteries SLI, traction and stationary. The table also gives the respective specific energies (by volume and weight). 

The most important market remains the car battery for starting, lighting and ignition (SLI), with approximately 50 x 10 units per year being sold in the USA. Lead/acid batteries are, however, also used on a very large scale for traction (e.g. delivery vans, milk floats, fork-lift trucks, industrial trucks — there are more than 100 000 such vehicles in the UK) and for stationary back-up or emergency power supplies. More recently, small lead/acid cells to compete with high-quality primary cells and nickel/cadmium cells for instruments, radios, etc., have also become available. 

In principle, all of the energy storage technologies presented here are feasible for traction application in road vehicles. Lead acid batteries play only a role in... 

Lead acid battery was invented in 1859 by Gaston Plante, and has been widely used throughout the world for more than 150 years [1], At present, all automobiles are equipped with one or more lead-acid battery. As for industrial application, lead-acid batteries have served as a backup for telecommunication system, office, and medical emergency power supply equipment [2]. Those are also used as traction battery for the electric forklifts [3]. In addition, those are used for electric moped in China and Asian area in recent years. In such ways, lead-acid batteries have become an inseparable device for our life. 

As an example Fig. 1.11 shows current distribution and heat generation in the course of a charging/discharging cycle as it is customary for vented lead-acid batteries in traction applications. 

Each standard needs an update following the technical development. So when the new international standard for dimensions of traction lead-acid cells lEC 60 254-2 was published and harmonized in the European Union to a European standard EN 60 254-1, DIN 43 595 was drawn back. In an additional technical information sheet, published by the German Battery Manufacturers Association, the (nominal) capacities in use were listed in relation to the cell dimensions. Table 2.3 shows the range of cell heights conforming to lEC (respective EN 60 254-2) together with the new series of higher capacities. 

After World War II most of the electric vehicles disappeared, and electric industrial trucks, streetcars, and boats and submarines remained the only field of application for traction batteries, mostly lead-acid batteries. England has kept about 40,000 electrically powered trucks in service to this day, mostly for service in rural areas, for milk delivery and the like. 

The main application of the lead-acid battery is vehicles for materials handling, such as forklift trucks, transporters, and so on, inside manufacturing plants and warehouses. Passenger transportation in areas where no pollution from exhaust gases can be tolerated is a further field of application for electric vehicles powered by batteries. Special machinery for lifting, cleaning, and other uses as well as electric boats, golf carts, and wheelchairs use and need the proven lead-acid traction battery. 

The relatively heavy weight of lead-acid batteries in relation to the useable performance has advantages for forklift trucks and other tractors (as counterweight or ballast), but is a great disadvantage for other traction systems such as electric road vehicles and mobile electric power supplies. Results in development with the aim to increase the specific energy and performance of battery systems and the minimization of their maintenance also have an impact on the employment of vehicles for materials handling. 

Capacity indicators for traction batteries are on the market in many variants, of different reliability, and adapted to different battery types. This is understandable since the useful capacity of a lead-acid battery is dependent on several parameters, such as physical and chemical impacts, design and type of the battery, aging, temperature, and load. The user s demand in any case is to have a capacity indicator, comparable with a fuel indicator in a motorcar. 

In the beginning of this chapter it was mentioned that the lead-acid battery, especially as a traction battery, will continue to maintain its premier position in the foreseeable future. Improvements are still possible. Besides improvements in performance and service hfe, we can expect the following coming improvements of traction batteries ... 

Figure 12.3 Charging time for lead acid and NiCd batteries. (A) Rectifier nominal current for charging traction lead acid cells GiS and PzS at 20°C (68°F) after discharge of (a) 80% and (b) 100% of C5. (B) Rectifier nominal current for charging of stationary lead acid cells OPzS, Gro, GroE at 20°C per 100 Ah K5 after discharge of (a) 80% and (b) 100% of C5 (operation conforming to DIN 40729). (C) Rectifier nominal current for charging R, TN/TS, and F type cells at 20°C per 100 Ah C5 after discharge of (a) 80% and (b) 100% of C5 (operation conforming to DIN 40729).

The major components in a lead-acid battery include a positive grid, negative grid, positive active material, negative active material, electrolyte, top lead, separator, and plastic container. The weight distributions of conunon SLI batteries and traction batteries are shown in Figure 1.18. 

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