ELECTRIC STORAGE BATTERY, The. Electrical energy is developed in com mercial quantity at the present day almost exclusively by means of a dynamo-electric machine, driven in turn by a steam engine, gas engine, water wheel or other prime mover. A plant of either of these kinds is somewhat complicated, so as to require skilled care in its operation; the electrical energy is available only while the machinery is in actual motion, and at such points as are connected with the gen erating plant by suitable electrical distributing circuits.
A device to supply electrical energy, under isolated conditions, and in such form as to be instantly available over long periods of time is therefore an almost imperative necessity and the device which science has developed for this purpose is known as the electric storage battery.
The storage battery does not, as its name might imply, store energy in the electrical form, but rather in the chemical, and hence it belongs to the general family of electrochemical apparatus.
of Storage Battery.— The essential "working parts") of a battery, broadly speaking, are three in number, namely, active material of the positive and negative plates, respectively, and the electrolytic solu tion, surrounding and electrically connecting the first two.
For the purpose of causing these working parts to function as a battery, there are required a number of subsidiaries, equally necessary, whose duties are mainly mechanical and elec trical in their nature. The active material con sists of a more or less cemented mass of powder, possessed in itself of very little mechanical strength. To retain this material in working condition there are required the "grids," which, as the name implies, are in most cases flat metallic plates of very open grid-like structure, with projections or °lugs° at one corner, to serve for making the electrical connections.
Since the plates of opposite polarity would quickly discharge themselves if allowed to touch, they must be kept apart, and this is invariably accomplished by the insertion of "separators"' between them.
As the electrolyte is almost invariably a liquid, rarely a jelly-like substance, there is required a retaining vessel, glass or hard rub ber jar, lead lined tank or steel jar, according as the case may be.
Reference to Figs. 24 and 25 will make clear the general construction; the plates, alternately positive and negative side by side, with sep arators between, and resting or hanging in a jar which hOlds the electrolyte. A very neces sary detail of design is that there shall be left sufficient clear space beneath the plates so that the sediment which gradually collects may settle there without contacting with the plates and causing a short circuit.
While attempts have been made to utilize all sorts of materials as "working parts," the successful combinations have narrowed down, until to-day there are practically only two in commercial operation.
The older and far the most generally used is known as the lead-sulphuric acid type; the newer as the alkaline, or, more generally, the Edison type. A description of each tyne sep arately will be followed by a brief analysis of its characteristics.
Equations of the Alkaline The Edison battery is chosen as the representative of the alkaline type because, although other varieties have been developed, and have met with limited success in Europe, yet Mr. Edison has carried the development of the type so much beyond any of the others' that to-day his is the only alkaline battery of commercial importance.
The positive active material consists of nickel peroxide; the negative of spongy, metal lic iron; the electrolyte of caustic potash or caustic soda solution. The chemical affinity of the sponge iron for oxygen constitutes the chief working force of the cell, diagrammat ically represented in Fig. 1, in which A and B are the positive and negative plates and C the active material, immersed in the electrolyte within the retaining vessel.