Page 160 - Automotive Engineering Powertrain Chassis System and Vehicle Body

Battery/fuel-cell EV design packages CHAPTER 6.1

The general form of control, with DC link inverter, for ‘memory effect’ suffered by Ni–Cads. The basic Li-ion
induction motors is shown diagrammatically at (f). The chemistry was initially redeveloped for automotive use
thyristors of the inverter are generally switched so as to by the French company SAFTSA, a leading battery
route current through the stator winding as though it manufacturer. Their advanced technology was then
were connected to a 3 phase AC. Frequency can be varied adapted to the e-Ka by Ford’s Research Centre in
by timing of pulses to the thyristors and is typically Aachen, Germany, with financial assistance for the pro-
5–100 Hz, to give a speed range of almost twice syn- ject from the German Ministry for Education and Re-
chronous speed. According to engineers from Chloride search. The battery pack consists of 180 cells with
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EV Systems Division, devices for building such an in- 28 kwh rating and weighs only 280 kg (615 lb). This is
verter are not yet available for current levels associated 30% the weight of the power equivalent in lead–acid
with EV traction. This situation may have already batteries, and substantially less than comparable
changed in the interim, however. Ni–Cads and Ni–MHs. In terms of volume the Ni-ion has
approximately half the bulk of all the other three.
6.1.5.4 Ford E-KA: Lithium-ion battery Batteries are divided into three individual sealed
power ‘troughs’, each with 30 modules containing six cells. One
trough is located in the engine compartment, with the
European Ford claim the first production-car use of other two on either side of the back axle. Nominal output
lithium-ion batteries in a road vehicle by a major player in of 315 V DC is transformed by a solid-state inverter to
the industry. The high energy density and power-to- 3 phase AC for the traction motor. Heat generated by the
weight ratio of these storage units puts a prototype internal resistance of these second-generation Li-ion
electric version of the small Ka hatchback, Fig. 6.1-17,on batteries is dissipated by one of two fluid cooling sys-
a par with the petrol-engined model in driving perfor- tems. A second independent system cools the drivetrain,
mance. Top speed is said to be 82 mph with acceleration to with a 65 kW (88 bhp) asynchronous motor followed by
62 mph in 12.7 seconds, although range between charges a fixed-ratio transmission driving the front wheels.
is still only 95 miles, but is extendible to 125 miles with Torque rating is 190 Nm (140 lb ft).
a constant speed of 48 mph. Performance of the e-Ka is enhanced by a 45 kg (100
Until now Li-ion batteries have been used mainly in lb) weight reduction to counter the battery load. The
small consumer electronic products like notebook com- roof and hood are of aluminium sandwich construction
puters, cellular phones, baby monitors and smoke with a thermoplastic filling, while the front brake calli-
detectors. Output per cell of 3.6 volts is some three pers with ceramics discs, rear drums, wheel rims and
times that of nickel–cadmium and nickel–metalhydride back axle are all in light alloy. Electric power steering
that they widely replace. They also retain full charge supplied by Delphi provides further weight saving, where
regardless of usage, can be recharged from zero to full an electronic control module regulates the assistance
capacity in 6 house with over 3000 repeated charge/ needed to minimize battery demand. Brake servo and
discharge cycles, and are immune from the so-called ABS system are also electric.

Fig. 6.1-17 Ford e-Ka.

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