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The Revival of the Battery-electric Vehicle
Page 112
Page 113
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THE obvious attractive features of the battery-electric vehicle, combined with the minimizing of its inherent limitations, give it certain of the advantages that to-day are bringing it back to popularity, but there are others which have appreciated in value under modern conditions, until they have become of national importance.
Before embarking upon the exploration of this avenue, however, it would be advisable to consider the uses from which the battery-electric is not debarred by the limitations just referred to. Its speed is low, therefore, it must be used only for short runs ; the supply of accumulated energy that it carries is relatively small, therefore it must work within a short radius of its headquarters ; it is heavy, accordingly hilly country is unfavourable, but this may be largely discounted in view of the fact that speed is of no great importance.
The two purposes which make no demands beyond these limitations are, of course, house-to-house collection in thickly populated areas and delivery in similar circumstances.
Many municipalities have for long employed electric refuse collectors ; numerous general-haulage requirements have for years been admirably filled by
E46 the type ; whilst for early milk delivery, particularly in good-class neighbourhoods, the electric—noiseless, odourless and clean—is without peer. Additionally, the fact that the machine in no way contributes to the expenses incurred by the ratepayer for street cleansing must not be overlooked. For refuse collection also, much of which is done, in many districts, during the early hours of the day, silence is a big asset.
Discussion of limitations has led to the introduction of advantages. For continual starting and stopping, the electric vehicle is ideally suited. The torque of the motor is more or less constant throughout its range of speed, and the elimination of the friction clutch is an important item on this class of work. The moving parts are few, all rotate, none reciprocates. The power is so smoothly generated that wear of the transmission mechanism and even of the tyres is reduced to the minimum.
The brushes can have a large area of contact, and when they do require renewal they are cheap and easy to replace. Worn commutators can be reconditioned with little less facility. Modern controller gear is lasting and subject to few derangements. The latest motor design affords a degree of efficiency, under all working conditions, that taxes the battery to the minimum.
The last-named has been vastly improved during the past few years. The life of the lead-acid 'type may be said, without exaggeration. to have been doubled ; that of the nickel-iron type is, of course, much longer, and these batteries, otherwise known as alkaline, are capable of withstanding more misuse and rough handling. They are, however, rather more expensive, also the voltage drops steadily from the commencement of the period of discharge, whereas, with the acid type, after the initial drop, it remains practically constant, until the cells are nearing complete exhaustion.
The ability of the alkaline battery to withstand a higher charging rate is not always regarded as being of great importance, because half the life of the vehicle is probably spent oil the road. Were the quick-charging accumulator to become a practicable proposition, the gain would not seem to be so great as might at first sight appear, for, to utilize it efficiently it would require to be charged during the hours when the generating stations were running at loads far nearer peak than is the case late at night.
It is sometimes put forward that the gassing of the accumulators is harmful to the goods contained in the vans when these happen to be edibles. For municipal purposes this would boe of no consequence, and, in any case, the negligible quantity of gas that comes
oil during discharge, being mainly hydrogen, at once dissipates.
In the process of charging, on the other hand, considerable gassing does take place, and it is essential that precautions be taken to guard against the possible consequences of this evil, amongst which risk of explosion is, perhaps, the most probable.
The question of charging brings us to what may be regarded as the funda, mental explanation of the recent revival of interest in this type of commercial vehicle. The output-capacity of our electricity-generating stations is governed by the maximum demand for current. In order to meet it, the plant may run at overload for short periods of every 24 hours. For longer periods it is generating at an economic rate ; but, for a very considerable portion of its life, its output is much below capacity. Could the fluctuating demand be levelled, fuel would be consumed more profitably and the returns on capital invested would• be higher.
With the establishment of the -Grid system this problem has become a matter of national importance. Surely
the increasing employment of the battery-electric vehicle must already be contributing in some part to its solution.
Already standard electric chassis are marketed which are equipped with valve-charging units, so that all that
has to be done at the completion of the day's work is to plug-in to the main A.G. supply. Alternatively similar charging sets may be installed at headquarters, thus eliminating costly transformers, etc. With 50-cycle three-phase alternating current at 400 and 230 volts available throughout the country, as it will be when the Grid is fully established, the vehicle equipped with its own charging unit will be able to have its batteries charged up at any point where the mains can be tapped.
It is gratifying to realize that the revival of the electric vehicle may be partly due to the appreciation by its users of the good that is being done to their country by the employment of a vehicle which originally derives its motive power from a source that is home produced.
Although the electric vehicle will not. like the horse, move on from one house to the next at a sign or a sound, it will do so practically at a touch. On all other counts it is, at least, the horse's equal, and on most, its superior, For the major part of its working life it is running nearly at full capacity, which, as has been pointed out in connection with generating plant, is a state of affairs eminently desirable from the economic point of view.