Edison NiFe Batteries:
Another widely used secondary cell is the alkaline cell, or nickel-iron battery (Ni-Fe), developed by the American inventor Thomas Edison in the 1900s. The principle of operation is the same as in the lead-acid cell except that the negative electrode consists of iron, the positive electrode is of nickel oxide, and the electrolyte is a solution of potassium hydroxide (KOH). The nickel-iron cell has the disadvantage of giving off hydrogen gas during charging. This battery is used principally in heavy industry applications. The Edison battery has a useful life of approximately ten years and produces about 1.15 V. The electrolyte of the Edison battery is about 21 per cent KOH, having, in addition, a small amount of lithium hydrate.
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 there- from will afford an intelligent comprehension of this invention:
"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 battery, is immediately re-formed in equal quantity; and therefore in effect is a CONSTANT element, not changing in density or in conductivity.
"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.
solution of potassium hydrate having, in addition, a small amount of lithium hydrate. The active metals of the electrodes --which will oxidize and reduce in this electrolyte without dissolution or chemical deterioration--are nickel and iron. These active elements are not put in the plates AS METALS; but one, nickel, in the form of a hydrate, and the other, iron, as an oxide.
"The containing cases of both kinds of active material (Fig. 1), and their supporting grids (Fig. 2), as well as the bolts, washers, and nuts used in assembling (Fig. 3), and even the retaining can and its cover (Fig. 4), are all made of nickel-plated steel--a material in which lightness, durability and mechanical strength are most happily combined, and a material beyond suspicion as to corrosion in an alkaline electrolyte....
"An essential part of Edison's discovery of active ma- setials for an alkaline storage battery was the PREPARATION of these materials. Metallic powder of iron and nickel, or even oxides of these metals, prepared in the ordinary way, are not chemically active in a sufficient degree to work in a battery. It is only when specially prepared iron oxide of exceeding fineness, and nickel hydrate conforming to certain physical, as well as chemical, standards can be made that the alkaline battery is practicable. Needless to say, the working out of the conditions and processes of manufacture of the materials has involved great ingenuity and endless experimentation."
"It will be seen at once that the construction of the two kinds of plates 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 1/2 inch wide by 3 inches long, and having a maximum thickness of a little more than 1/8 inch. The positive or nickel plate (Fig. 6) is seen to consist of two rows of round rods shaped like pencils, thirty in number, held in a vertical position by a steel support-frame. The pencils have flat flanges at the ends (formed by closing in the metal case), by which they are supported and electrical connection is made. The frame is slit at the inner horizontal edges, and then folded in such a way as to make individual clamping-jaws for each end- flange. The clamping-in is done at great pressure, and the resultant plate has great rigidity and strength.
"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 1/4 inch in diameter by 4 1/8 inches long, and 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 exceeds the most cautious 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 sawed lengthwise. The vertical bounding walls are edges of the perforated metal containing tube; the dark horizontal lines are layers of nickel flake, while the light-colored thicker layers represent the nickel hydrate. It should be noted that the layers of flake nickel extend practically unbroken across the tube and make contact with the metal wall at both sides. These metal layers conduct current to or from the active nickel hydrate in all parts of the tube very efficiently. There are about three hundred and fifty layers of each kind of material in a 4 1/8 -inch tube, each layer of nickel hydrate being about 0.01 inch thick; so it will be seen that the current does not have to penetrate very far into the nickel hydrate--one-half a layer's thickness being the maximum distance. The perforations of the containing tube, through which the electrolyte reaches the active material, are also shown in Fig. 7."
There are several more pages if any interest is expressed...
Although Nickel is expensive (nickel brazing rod, pre-'83 Canadian 5-cent pieces, etc) these batteries can be deep-cycled daily for 50 years by just occasionally adding water and Iron-oxide. -Ron
"I'd give my left arm to be able to play guitar like Eric Clapton"
