XVIII
EDISON'S NEW STORAGE BATTERY
Edison, His Life and Inventions, vol. 2 | ||
18.
XVIII
EDISON'S NEW STORAGE BATTERY
GENERICALLY considered, a "battery'' is a device which generates electric current. There are two distinct species of battery, one being known as "primary,'' and the other as "storage,'' although the latter is sometimes referred to as a "secondary battery'' or "accumulator.'' Every type of each of these two species is essentially alike in its general make-up; that is to say, every cell of battery of any kind contains at least two elements of different nature immersed in a more or less liquid electrolyte of chemical character. On closing the circuit of a primary battery an electric current is generated by reason of the chemical action which is set up between the electrolyte and the elements. This involves a gradual consumption of one of the elements and a corresponding exhaustion of the active properties of the electrolyte. By reason of this, both the element and the electrolyte that have been used up must be renewed from time to time, in order to obtain a continued supply of electric current.
The storage battery also generates electric current through chemical action, but without involving the constant repriming with active materials to replace those consumed and exhausted as above mentioned. The term "storage,'' as applied to this species of battery, is, however, a misnomer, and has been the cause of much misunderstanding to nontechnical persons. To the lay mind a "storage'' battery presents itself in the aspect of a device in which electric energy is stored, just as compressed air is stored or accumulated in a tank. This view, however, is not in accordance with facts. It is exactly like the primary battery in the fundamental circumstance that its ability for generating electric current depends upon chemical action. In strict
The storage battery, as a commercial article, was introduced into the market in the year 1881. At that time, and all through the succeeding years, until about 1905, there was only one type that was recognized as commercially practicable—namely, that known as the lead-sulphuric-acid cell, consisting of lead plates immersed in an electrolyte of dilute sulphuric acid. In the year last named Edison first brought out his new form of nickel-iron cell with alkaline electrolyte, as we have related in the preceding narrative. Early in the eighties, at Menlo Park, he had given much thought to the lead type of storage battery, and during the course of three years had made a prodigious number of experiments in the direction of improving it, probably performing more experiments in that time than the aggregate of those of all other investigators. Even in those early days he arrived at the conclusion that the lead-sulphuric-acid combination was intrinsically wrong, and did not embrace the elements of a permanent commercial device. He did not at that time, however, engage in a serious search for another form of storage battery, being tremendously occupied with his lighting system and other matters.
It may here be noted, for the information of the lay reader, that the lead-acid type of storage battery consists
In the year 1900, when Edison undertook to invent a storage battery, he declared it should be a new type into which neither sulphuric nor any other acid should enter. He said that the intimate and continued companionship of an acid and a metal was unnatural, and incompatible with the idea of durability and simplicity. He furthermore stated that lead was an unmechanical metal for a battery, being heavy and lacking stability and elasticity, and that as most metals were unaffected by alkaline solutions, he was going to experiment in that direction. The soundness of his reasoning is amply justified by the perfection of results obtained in the new type of storage battery bearing his name, and now to be described.
The essential technical details of this battery are fully described in an article written by one of Edison's laboratory staff, Walter E. Holland, who for many years has been closely identified with the inventor's work on this cell The article was published in the Electrical World, New York, April 28, 1910; and the following extracts therefrom
"The `A' type Edison cell is the outcome of nine years of costly experimentation and persistent toil on the part of its inventor and his associates....
"The Edison invention involves the use of an entirely new voltaic combination in an alkaline electrolyte, in place of the lead-lead-peroxide combination and acid electrolyte, characteristic of all other commercial storage batteries. Experience has proven that this not only secures durability and greater output per unit-weight of battery, but in addition there is eliminated a long list of troubles and diseases inherent in the lead-acid combination....
"The principle on which the action of this new battery is
based is the oxidation and reduction of metals in an electrolyte
which does not combine with, and will not dissolve,
either the metals or their oxides; and an electrolyte, furthermore,
which, although decomposed by the action of the
FIG. 1
[Description: An illustration of the containing cases used with the
lead-acid storage battery.]
"A battery embodying this basic principle will have features of great value where lightness and durability are desiderata. For instance, the electrolyte, being a constant factor, as explained, is not required in any fixed and large amount, as is the case with sulphuric acid in the lead battery; thus the cell may be designed with minimum distancing of plates and with the greatest economy of space that is consistent with safe insulation and good mechanical design. Again, the active materials of the electrodes being insoluble in, and absolutely unaffected by, the electrolyte, are not liable to any sort of chemical deterioration by action of the electrolyte—no matter how long continued....
"The electrolyte of the Edison battery is a 21 per cent.
"The containing cases of both kinds of active material
(Fig. 1), and their supporting grids (Fig. 2), as well as the
FIG. 2
[Description: Illustration of supporting grids used with the Edison battery.]
"An essential part of Edison's discovery of active materials
FIG. 3
[Description: Illustration of the nuts and bolts used in assembling the Edison battery.]The article then treats of Edison's investigations into means for supporting and making electrical connection with the active materials, showing some of the difficulties encountered and the various discoveries made in developing the perfected cell, after which the writer continues his description of the "A'' type cell, as follows:
"It will be seen at once that the construction of the two kinds of plate is radically different. The negative or iron plate (Fig. 5) has the familiar flat-pocket construction. Each negative contains twenty-four pockets—a pocket being
FIG. 4
[Description: Illustration of the retaining can and cover used in the Edison battery.]FIG. 5
[Description: Illustration of the iron or negative plate used in the "A" type cell.]"The perforated tubes into which the nickel active material is loaded are made of nickel-plated steel of high quality. They are put together with a double-lapped spiral seam to give expansion-resisting qualities, and as an additional precaution small metal rings are slipped on the outside. Each tube is ¼ inch in diameter by 4 ⅛ inches long, add has eight of the reinforcing rings.
"It will be seen that the `A' positive plate has been given the theoretically best design to prevent expansion and overcome trouble from that cause. Actual tests, long continued under very severe conditions, have shown that the construction is right, and fulfils the most sanguine expectations.''
Mr. Holland in his article then goes on to explain the development of the nickel flakes as the conducting factor in the positive element, but as this has already been described in Chapter XXII, we shall pass on to a later point, where he says:
"An idea of the conditions inside a loaded tube can best
be had by microscopic examination. Fig. 7 shows a magnified
section of a regularly loaded tube which has been
FIG. 6
[Description: Illustration of the positive or nickel plate used with the
"A" type cell.]
FIG. 7
[Description: Image of the magnified section of a regulary loaded tube, part of the "A" cell battery.]In conclusion, the article enumerates the chief characteristics of the Edison storage battery which fit it preeminently for transportation service, as follows: 1. No loss of active material, hence no sediment short-circuits. 2. No jar breakage. 3. Possibility of quick disconnection or replacement of any cell without employment of skilled
XVIII
EDISON'S NEW STORAGE BATTERY
Edison, His Life and Inventions, vol. 2 | ||