Batteries vehicle traction

Starting, lighting, and ignition batteries Vehicle traction battery... 

These materials are introduced in Chapter 5 and only brief mention of them is necessary here. It is important to appreciate that polymer electrolytes, which consist of salts, e.g. Nal, dissolved in solid cation coordinating polymers, e.g. (CH2CH20) , conduct by quite a different mechanism from crystalline or glass electrolytes. Ion transport in polymers relies on the dynamics of the framework (i.e. the polymer chains) in contrast to hopping within a rigid framework. Intense efforts are being made to make use of these materials as electrolytes in all solid state lithium batteries for both microelectronic medical and vehicle traction applications. 

Safety and Hazards. The linear carbonate solvents are highly flammable with flash points usually below 30 °C. When the lithium ion cell is subject to various abuses, thermal runaway occurs and causes safety hazards. Although electrode materials and their state-of-charge play a more important role in deciding the consequences of the hazard, the flammable electrolyte solvents are most certainly responsible for the fire when a lithium ion cell vents. The seriousness of the hazard is proportional to the size of the cell, so flame-retarded or nonflammable lithium ion electrolytes are of special interest for vehicle traction batteries. 

Since a considerable proportion of all petroleum is consumed in vehicle traction - a particularly inefficient way of extracting energy from a scarce resource which simultaneously causes severe environmental pollution in urban areas - the possibility of replacing vehicles driven by internal combustion engines with battery-powered electric transport is under active consideration, and the development of advanced batteries for this purpose is being pursued in a number of countries. Since batteries for electric vehicles (EVs) must be transported as part of the vehicle load, they require high power/mass ratios in addition to high cycle efficiency. 

Vehicle traction batteries 20-630 kWh (3 MWh) Fork-lift trucks, milk floats, locomotives (submarines)... 

However, the introduction in 1913 by Ford of the mass-produced car completely ousted the battery for vehicle traction. The reason is clearly demonstrated in Fig. 

Vehicle traction batteries 20-630 kWh forklift trucks, locomotives... 

Deep cycle and traction batteries. These models are used in electric vehicles. Traction batteries are designed to power vehicles. 

VRLA as an EV battery. The traction battery in EVs has long been identified as the key to commercial success of this product line motors, transmissions, and silicon components can all attain reasonable economies of scale and technology, but the component which is the most resistant to cost-reduction is the battery. This is a critical point since batteries comprise approximately 20% of the total cost of lead-acid-powered vehicles and about 55% of the cost of Ni-MH vehicles (see Fig. 11.28) [2]. Therefore, batteries provide the best opportunity to reduce the overall cost of EVs. With the battery cost of advanced technologies such as Ni-MH greater than the vehicle cost, there is a clear need for a low-priced battery such as lead-acid can offer. 

Specification of Test Procedures for Electric Vehicle Traction Batteries, EUCAR, December 1996. 

Work at Harwell has concentrated on scaling up the lithium polymer battery technology for use in electric vehicle traction batteries. The project, supported by the Commission of the European Communities, has systematically scaled up the cell active area. The various cell sizes are shown in Figure 6.33. The larger cells were used to construct two 80 A h units which are shown in Figure 6.34. The results of the project have highlighted the need for capacity balance and excellent cell-to-cell reproducibility. 

The performance of the experimental vehicles was impressive and confirmed the technical feasibility of the sodium/sulphur battery for traction applications. At the same time it was recognised that for commercial viability it would be necessary to improve the volumetric energy density of the battery and to custom-design it for a particular vehicle, as well as extending the lifespan and reliability of the cells. These developments involve problems of cell and battery design and further work in Britain has been directed towards these goals. 

The central problem which confronts all design engineers is to design a product which meets a stated performance and cost specification, within constraints imposed by the laws of science, the properties of materials and known engineering practice. The particular difficulty in the present instance is that the performance specification for vehicle traction batteries tends to be... 

Before it is possible to design a vehicle traction battery it is necessary to settle on a cell design. The optimisation of cell design is a central issue which must tcike into account not only the technical constraints within the cell, listed above, but also constraints imposed by the vehicle design and intended duty cycle as well as considerations of safety and production engineering. Particularly important parameters are ... 

Figure 4.10 Present state designs of vehicle traction batteries and battery modules.

Those applications in which the secondary battery is discharged (similar in use to a primary battery) and recharged after use, either in the equipment in which it was discharged or separately. Secondary batteries are used in this manner for convenience, for cost savings (as they can be recharged rather than replaced), or for power drains beyond the capability of primary batteries. Most consumer electronics, electric-vehicle, traction, industrial truck, and some stationary battery applications fall in this category. 

Specific gravity may range from 100 to 150 points between full charge and discharge depending on cell design A—electric vehicle battery B— traction battery C—SLI battery D—stationary battery. 

The Gould/Westinghouse battei7 is the nearest to commercial production of those being developed by various companies. However, further improvement in cycle life, charging systems and thermal management are needed before the batteries can find use in vehicle traction applications. 

These batteries are under evaluation for application to electric vehicle traction. The target energy density for this application is 80Wh/kg" and 70Wh/kg has already been achieved in trials. The target power density is 200 W h/kg and the target cycle life is 1000 plus cycles. Other applications include camcorders, cellular telephones and computers. This battery may overtake nickel-cadmium types in output and applications by the end of the century. 

Although electric vehicles are only a special application for traction batteries, the general interest in them may justify their own separate section. 

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. 

This cell system is also under active development for EV traction. Realistic targets are reported as 80 Wh/kg for energy density, 200 W/kg for power density, and a cycle life of over 1000. The Ovonic Battery Co have already demonstrated 67 Wh/kg for a 250 Ah battery, and Panasonic have reported a similar value for a 130 Ah unit. Thermal management and cost are likely to be the key factors limiting development of nickel-metal hydride technology for electric vehicles. 

Accumulators in increased safety - e - cover traction batteries for locomotives in coal mines (see Fig. 6.4) as well as batteries for forklifts in chemical plants or other transportation vehicles running in hazardous areas powered by their own energy storage system. Much smaller accumulators are used as a mains-independent power source for handlamps and caplamps (Fig. 6.65) used in potentially explosive atmospheres. 

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