The Scope of the Battery-electric Vehicle
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THE large number of batteryeIectrics to be seen on the streets of any city is a sure pointer to the increasing interest being taken in this form of transport. There is a number of reasons for this interest, of which probably the most important is the economic, the vehicles being very cheap to run. The other features of the type, such as silence, cleanliness and freedom from fumes, make a considerable appeal to the discriminating user and those with whom he deals.
The field of the battery-electric is specialized, as the vehicle is most suited for services with a limited daily mileage, generally accompanied by a large number of stops and starts. It will, therefore, usually be found working on retail. delivery rounds, especially in those trades where frequent and concentrated deliveries have to be made, such as the dairy, bakery and laundry. It is also used successfully for the house-to-house delivery of coal.
In many special businesses it is found to be invaluable, and numerous instances could be cited, such as travelling libraries, etc.
Certain factors in the design of the vehicle limit its duties generally to such as are given above, and to ignore these points is to court disappointment.
The Most Important Unit.
The most important unit is the battery, which resembles a starter battery but is larger and more robust. This, unless very larg& cannot hold a charge of electricity sufficient for more than 35 miles to 40 miles. The majority of batteries fitted is smaller than this, and one to give a range of 25 miles to 30 miles is the most usual size. It is desirable to have the smallest battery reasonably possible, as this item is heavy and any excess will reduce the pay-load which the vehicle can carry. Due regard must, of course, be given to a sufficient margin of capacity, as even one tow-in, by reason of a fully discharged battery, will lead to disappointment with the type of vehicle.
Those who think that the range offered is too small should consider if many of their rounds really do call for a larger range or if they could not be rearranged to make the majority of them come Well within the normal limits of the ,battery of reasonable size.
Adopting a new type of vehicle may mean adopting new methods as well; this, however, is not inherent to the type of vehicle but is common to all changes in methods of transport if the maximum use and economy of the type adopted are to be made available.
Some years ago a prominent and large dairy company in the Midlands tried out this form of transport and found that it involved rearranging the rounds. The economy of the battery-electric was so marked that the policy has been to replace, whenever possible, all other types of transport in favour of the batteryelectric.
Advantages of the Type.
Whilst economy of operation will naturally be the first consideration, the other factors are of considerable importance. Silence is obtained by the absence of any reciprocating parts, the drive usually consisting of an electric motor coupled, through universal joints, to a propeller shaft and normal back axle. The electric motor is inherently a silent unit, as are the propeller shaft and back axle. There is an absence of clutch and gearbox, these being rendered unnecessary, as the electric motor can exert full torque from standstill.
As the motor is solidly connected to the road wheels the unit rotates only when the vehicle is moving, and at a speed which is proportional to that of the vehicle. A further characteristic of the electric motor is that as the speed increases the torque decreases, so that there is a limit to the speed at which it can drive the vehicle.