Vehicle traction

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. 

Table 3. Technical targets 50 kWe (net) integrated fuel cell power systems operating on Tier 2 gasoline containing 30 ppm sulfur, average Oncluding fuel processor, stack, auxiliaries) (Excluding gasoline tank and vehicle traction electronics) All targets must be achieved simultaneously and are consistent with those of FreedomCAR ...

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

During braking operation, regenerative or dissipative braking on resistors is provided, depending on the line receptivity. The vehicle traction system is constituted by two IGBT power converters each one supplying an asynchronous traction motor. 

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. 

Laboratory cells and small prototypes have demonstrated the performance levels required for such applications as electric vehicle traction, large scale stationary storage and space power. In these situations it is possible to envisage the use of the elevated temperature form of the technology since straightforward thermal management techniques can be used and. 

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 ... 

The importance of electro-nuclear energy should, however, be considered on the world rather than the national scale, especially when the following points are taken into account the very marked increase in the demand for energy, the increasing cost of classic fuels and the need to use the latter more and more for specialized purposes (chemical, iron and steel industries, motor-vehicle traction, etc.). 

Unfortunately, despite a substantial research elTort over some 30 years since the possible applications of fuel cells in power generation and vehicle traction were first recognized, the progress towards a fuel cell operating on a primary fuel has not been rapid. In particular, it has not proved possible to design catalysts for the anodic oxidation of hydrocarbons which even approach the required performance. Even at extreme pH and elevated temperatures, such oxidations occur at only low current densities and at substantial overpotentials with all investigated electrode materials. 

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

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

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. 

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. 

Developments in flat or tubular plate designs for lead-acid electric vehicle traction has in recent years concentrated on improving energy density and power... 

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