112Rechargeable Battery Vehicles

Rechargeable battery vehicles can also be divided into several different categories. For example, there are electric bicycles, secondly there are the low speed vehicles (LSVs) which form a class of vehicle in the USA and Canada, with maximum speeds of 40 kph (25 mph), and thirdly conventional road vehicles using rechargeable batteries. In addition there are special purpose delivery vehicles and vehicles such as fork lift trucks. There are also the small four-wheeled carriages used by the infirm which can be ridden on the pavement, and are narrow enough to fit through normal front doors. Other vehicles, such as powered wheel chairs, could also be mentioned.

11.2.1 Electric bicycles

Electric bicycles are probably the most popular type of battery electric vehicle. For example, thousands are used in China. There are many different manufacturers and types, with a very

Electric Vehicle Technology Explained James Larminie and John Lowry © 2003 John Wiley & Sons, Ltd ISBN: 0-470-85163-5

interesting range of power methods: hub motors in the front or back wheels, and drives on the pedal cranks are the most common variations. In most European and North American countries it is becoming a standard regulation that these bikes must be of the 'pedal-assist' type. This means that they cannot be powered by the electric motor alone. If they can be ridden under electric power only, then they count as motorbikes, and attract a host of extra regulations and taxes. However, the regulatory situation is somewhat fluid, varied and changeable, which is something of an impediment to the development of this market.

For example, in the UK 'electric power' only bicycles are still legal (in 2003), but the power must cut out once the cycle reaches a speed of 15mph. The maximum allowed motor power is 200 W, the maximum weight is 40 kg, and the riders must be aged 14 years or over. However, this law is liable to change in the near future in favour of pedal assist mode only.

These regulations mean that the controllers on electric bikes nearly always include a sensor of some kind. Often there will be a torque sensor, on the pedal crank. This works with the motor controller, and ensures the rider is putting in some effort before allowing the motor to provide any power. Speed sensors will also often be fitted, to cut the electric power once a set speed is reached, 15 mph in the UK.

Although the large cycle manufacturers, such as Giant of Taiwan, are including electric cycles, the market is currently dominated by smaller businesses supplying a fairly local region. For example, in the UK one notable manufacturer is Powabyke Ltd., and one of their cycles is shown in Figure 11.1. Some technical details of their range of

Figure 11.1 Electric bicycle

Table 11.1 The specification for the Powabyke range of electric cycles

Wheels

Frame

Motor

Speed control

Range, pedal assist mode

Battery

Gears (for pedalling) Battery charge time Mode Charger

Weight including battery Current cost

Pure power, pedal assist or pedal only, switchable 36 V mains charger 39 kg

About £699.99 depending on specification

24 or 26 inch 17 inch

200 W Hub Motor Handlebar-mounted twist throttle Claimed 50 km, approximately 36 V, 14 Ah VRLA battery 5, 21 or 24 speed 8 h standard cycles are given in Table 11.1, though they also produce other types, such as a foldable cycle.

The development of reliable electric bikes could in itself have a significant impact. It may encourage people to use bikes rather than their conventional internal combustion engine vehicles. A survey by the manufacturers showed that the average Powabyke covered 1200 miles per annum, replaced 3 car journeys per week, provided a journey time faster than a bus and cost less than 1.5 pence per mile to run.

Use of this type of vehicle could be increased with encouragement from governments and councils in the form of special cycle tracks. The use of electric bikes would undoubtedly lead to less vehicle traffic and decreased pollution.

11.2.2 Electric mobility aids

One area of application that the demographics of western countries indicate must steadily grow for the foreseeable future is mobility aids for the elderly and infirm. The sort of vehicle we are talking about here is shown in Figure 11.2, a carriage for those who can take a few steps, but need help from technology to retain their independence. There is a wide range in this class, from small three-wheelers to larger vehicles with a claimed range of 40 miles, and tougher wheels, for people who need to get about country lanes. Table 11.2 gives the outline technical details of a middle range machine such as that of Figure 11.2.

11.2.3 Low speed vehicles

Low speed vehicles (LSVs) are an environmentally friendly mode of transport for short trips, commuting and shopping. In the USA, for example, 75% of drivers are believed to drive round trips of less than 40 km per day. In rural areas the lower traffic density would enable these to be used fairly easily. In towns and cities it would be worthwhile for governments and local authorities to ensure that proper lanes for this type of vehicle were made available, and where possible tax incentives are used to encourage their use.

Figure 11.2 Mobility aid for shopping trips and similar journeys near home

Table 11.2 Details of a shopping carriage for the infirm, such as that shown in Figure 11.2

Length

Width

Height

Weight

Batteries

Motor power

Drive

Maximum speed Maximum incline Range

1.19m

0.6m

0.91m

65 kg, 85 kg with batteries 2 of 12 V, 28 Ah (20 hour rate) 370 W continuous Rear wheel drive, one motor 6 kph forward, 2 kph reverse 10°C

30 km (claimed, on level ground)

These vehicles are particularly targeted at fairly active retired people, who still want to get about to see their friends, but who do not travel so far, are not in such a hurry, and value a peaceful neighbourhood. The demographics of most western countries show there is little doubt that the market for this type of vehicle will grow steadily.

An example LSV is shown in Figure 11.3. The specification of a typical four seat vehicle of this type is given in Table 11.3.

Figure 11.3 An example of the low speed vehicle (LSV) type of electric car

Table 11.3 Specification of a typical low speed electric vehicle

Length

3075 mm

Width

1400 mm

Height

1750 mm

Wheelbase

2635 mm

Curb weight

560 kg

Payload

360 kg

Ground clearance

150 mm at curb weight

Minimum turning radius

4080 mm

Range

64 km

Acceleration

0 to 40 kph, 6 s

Hill climbing capability

21%

11.2.4 Battery powered cars and vans

There is a range of vehicles, vans, cars and buses that have been used in recent years. Most have ranges under 100 km, and the best possible range of a rechargeable battery vehicle such as the GM EV1 is 200 km. While this market will no doubt always continue at a small level, there is no evidence of much growth, and indeed recent developments in California, mentioned in the final section, mean that this market may well decline.

An example is the Ford Th!nk shown in Figure 1.6. This is a two-seat car using a steel chassis with thermoplastic body panels. It has a top speed of 90kph and accelerates to 48 kph in 7 seconds. It uses 240 kg of NiCad batteries and has an overall weight of 940 kg. Despite a very expensive development programme, this car is no longer in production, as Ford see the future more in hybrids and fuel cell cars.

Peugeot have always been very active in electric vehicles, and work with vans as well as cars. Two example vans are the 106 and the Partner. The Partner van is illustrated in Figure 11.4 and the specification of both is given in Table 11.4. There is also a 106 electric car, which has a similar specification to the van.

The Peugeot electric vehicles are examples of conventional vehicles converted to electric vehicles. Their range is doubtless adequate for uses such as city deliveries, but is less than might have been obtained with a purpose-built electric vehicle. This is undoubtedly a trade-off of cost against range.

When designing their EV1 vehicle, as shown in Figure 11.5, General Motors took another philosophy altogether. The GM EV1 is a rechargeable battery powered two-seater car, which represents probably the most advanced electric vehicles using rechargeable

Figure 11.4 Peugeot Partner battery electric van. (Photograph reproduced by kind permission of Peugeot S.A.)

Table 11.4 Details of Peugeot battery electric vans

106 Van Partner Van

Table 11.4 Details of Peugeot battery electric vans

106 Van Partner Van

Motor type

Leroy Somer DC separate excitation

Leroy Somer DC separate

20 kW

excitation 28 kW

Max. motor torque

127 Nm from 0-1600rpm

180Nm from 0-1550rpm

Max. motor speed

6500 rpm

6500 rpm

Motor cooling

Forced air ventilation

Transmission

Front wheel drive, epicyclic reduction to differential

Steering

Rack and pinion, power assisted

Suspension, front

Independent with MacPherson type struts

Suspension, rear

Independent with trailing arms and torsion bars

Front brakes

Servo-assisted discs

Rear brakes

Servo-assisted drums

Tyres

165/70 x 13

165/60 x 14

Maximum speed

90 kph

96kph

Range (urban)

72 km

64kph

Restart gradient

22%

Battery type

NiCad, 100 Ah

Voltage

120 V

160V

Charger

3 kW integral with vehicle 240 V,

3 kW integral with vehicle 240 V,

13 A, AC supply

13 A, AC supply

Charging time

7h

9 hours

Energy consumption

20 kWh/100km

28 kWh/100km

Length

3.68m

4.11 m

Width

1.59m

1.69 m

Height

1.38m

1.81 m

Kerb weight

1077kg

1450kg

Payload

300 kg

500kg

Payload volume

0.92 m3

3 m3

batteries. It was purposely designed through and through as an electric vehicle and is not a modified IC engine vehicle. It was introduced in 1997, initially using lead acid batteries; more recent versions have used NiMH batteries to give an extended range.

We have already met this car when considering vehicle modelling in Chapter 7. It has the lowest drag coefficient of any production car (Cd = 0.19) and uses very low rolling resistance tyres. The vehicle was produced in limited numbers and could only be leased rather than bought. To the dismay of electric vehicle enthusiasts, the EV1 was recently taken off the market. The recent decision of the California legislature to draw back from its requirement on manufacturers to produce fully 'zero emission' vehicles has probably made this decision permanent. The existing examples will no doubt become valuable collectors' items in the years to come, because it is a very interesting car with many exciting technical features. The EV1 is illustrated in Figure 11.5.

Figure 11.5 The groundbreaking General Motors EV1 battery electric car (reproduced by kind permission of General Motors Inc.)

The EV1 is powered by a 102 kW, three-phase AC induction motor and uses a singlespeed dual reduction gear set with a ratio of 10.946:1. The battery pack consists of 26 valve-regulated high-capacity lead-acid batteries, each 12 V and 60 Ah. The EV1 can be charged safely in all weather conditions with inductive charging. Using a 220 V charger, charging from 0 to 100% takes from five-and-a-half to six hours. The EV1 with the high-capacity lead-acid pack has an estimated real-world driving range of 50 to 90 miles, depending on terrain, driving habits and temperature (see Section 7.4.2.3). The range with the optional NiMH pack is even greater. Again, depending on terrain, driving habits, temperature and humidity, estimated real-world driving range will vary from 75 to 130 miles.

Braking is accomplished by using a blended combination of front hydraulic disk and rear electrically applied drum brakes and the electric propulsion motor. Regenerative braking is used, extending the vehicle range by partially recharging the batteries.

The vehicle's body weighs 132kg and is less than 10% of the total vehicle weight, which is 1400 kg, of which the battery weight is nearly 600 kg. The 162 pieces are bonded together into a unit using aerospace adhesive, spot welds and rivets.

The exterior body panels are dent and corrosion-resistant. They are made out of composites and are created using two forming processes known as sheet moulding compound (SMC) and reinforced reaction injection moulding (RRIM).

The EV1 is designed to be highly aerodynamic, saving energy and allowing a lower level of propulsion power that sends the vehicle further. The rear wheels are 9 inches closer together than the front wheels, which allows for a tear-drop body shape that lessens drag, as explained in Section 8.2.2.

The EV1 has an electronically regulated top speed of 80mph (130kph). It comes with traction control, cruise control, anti-lock brakes, airbags, power windows, power door locks and power outside mirrors, AM/FM CD/cassette, and tyre inflation monitor system. The vehicle also offers programmable climate control, an electric windshield defogger/de-icer, a rear window defogger and centre-mounted instrumentation.

The EV1 does not require a conventional key to unlock the door. A five-digit personal identification code is entered on the exterior keypad to allow access. No key is needed to start the car. The same five-digit code is entered on the centre console's keypad to activate the car.

The EV1 undoubtedly has as good performance and range as can be achieved economically using commercially available rechargeable batteries. The advanced performance clearly illustrates the benefits of designing the vehicle as an electric car rather than simply converting an existing vehicle. However, even this highly advanced design could not stand up to the market competition. The development in hybrid electric/ICE powered vehicles has probably also been a major contribution to its failure as a profitable product with significant sales.

The range of rechargeable battery vehicles is normally limited to below 150 km and at best 200 km. The use of batteries such as the Zebra battery or lithium chloride batteries could increase range further by 30%. Clearly, for a very much greater range a new generation of batteries is required.

Although the major manufacturers are losing interest in battery vehicles, the new low speed vehicles and electric bikes are making headway, as is the market for vehicles for the elderly and infirm, and it is in this area where future development is likely to take place.

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