Car battery traction

A certain performance is necessary for a battery to perform satisfactorily in any duty and we therefore need to define characteristics which may be measured and used to judge whether a battery is suitable for a particular application. Moreover in some cases, e.g. a car traction battery, no battery system presently available has all the essential properties. Hence it is important to understand how the characteristics depend on the choice of electrode reactions and on the design of the cell. It will also be clear that the various battery characteristics are not independent of each other and commonly a change of design to improve one will have an adverse effect on another. 

Energy densities for these larger batteries normally lie in the 20—30 Wh kg range although the contractors in the US Department of Energy car traction battery programme now claim values of 37—42 Wh kg for test Pb/acid units. 

Motive power (traction) batteries are industrial batteries used to power in-house transport vehicles fork-lift trucks, electric cars, mining equipment, etc. 

The sodium/sulphur system is being discussed for load levelling and car traction and is believed to be close to commercial production in the UK as a traction battery for commercial vehicles. The overall cell reaction is usually written... 

The degradation and aging mechanism depend on several factors [36,37]. At present the guaranteed calendar lifetime of a lithium battery ranges from 2 years (e.g. Sam) to 8 years (e.g. Ampera, Volt) depending on the car s manufacturer. An average lifetime for traction batteries of 10 years is still a development target, which have not been reached and demonstrated at a practical level. But of course, a battery can also be used below 80% of its nominal capacity. A second use phase of batteries, e.g. for stationary applications, has not been considered. 

Largely for reasons of cost, low maintenance requirements and proven technology, lead-acid batteries continue to dominate the traction battery market. The closest competitors, in specialist applications, are various nickel-based systems. For stationary batteries, used as a standby power source, the market is more closely divided between lead-acid and nickel-cadmium batteries. At the same time, new applieations have opened up in recent years for lead-acid batteries in electric-powered support vehicles (in recreational and industrial uses) and a potentially large new market in electric cars beckons (see Chapter 18, for a discussion of this and other new... 

SLI batteries (starting, lighting and ignition) 100-600 Wh Cars, trucks, buses, tractors, lawn mower traction... 

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. 

When substantial amounts of traction are delivered both by the battery and by the fuel cell, the system is called a hybrid system. The most advantageous set-up in this case should allow recharging of the battery when the vehicle is operated on the fuel cell at less than full power. For this configuration, there may be an additional option to recharge the battery from external sources when the car is parked (Bitsche and Gutmann, 2004 Suppes et al, 2004). Figure 4.1 shows some possible hybrid layouts. 

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 the light traction sector, the only marketable products in Germany are also manufactured by SFC Energy. They are based on the DMFC EFOY Pro Series. These devices are referred to as range extenders, internal chargers for the batteries of electric scooters or small electric cars with a maximum electric power of 90 W, which make the range of these vehicles greater. 

The technical overview of passenger cars with fuel cells is presented in Table 36.5. 7dl of the fuel ceU passenger cars presented here use a PEMFC, as high power density is needed for this application. The fuel ceU power is between 63 and 100 kW. The energy storage system is usually a lithium ion battery or an NiMH battery. A supercapacitor is only used once. Information about the hybridization concept is not provided in the literature. The hybridization degree, if it can be calculated, is between 0.17 and 0.30. For values lower than 0.50, the fuel cell delivers the majority of the traction power, for instance, during acceleration. 

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