| || || |
| || |
| || || |
From the 1926 book Edison, the Man and His Work.
… during these earlier years …, Edison was working upon cylindrical phonographic records; upon an improved form of the business phonograph, the new feature of which was that dictated matter could be repeated and corrections might thus be made; upon an electric motor for operating the business phonograph (or dictating machine) on commercial electric-lighting circuits.
His chief interest at this period was, however, centered in his long and arduous campaign to realize his idea of an alkaline storage battery.
This storage battery was probably the hardest nut he ever tried to crack.
Like all other electric batteries whatsoever, the so-called storage battery derives, of course, from the primary battery—better known as the voltaic battery, since the principle of its action was discovered by Alessandro Volta.
A primary battery is composed of a group of primary cells. Broadly speaking, a primary cell has for its component parts two different metals (known as the elements) associated with a chemical compound (termed the electrolyte). In the simple form of its modern development, the primary cell has a piece of zinc and a piece of copper clipped into a solution of dilute sulphuric acid.
A chemical action is set up; the zinc piece is gradually dissolved away; electric energy is produced.
More complex in structure is the “dry” cell, generally familiar through its use for electric bells, for flashlights, in motor-boats and motor-cars, and in radio receiving-sets. “Dry” it is not, except in a relative sense. Its cylindrical zinc container is the negative element; through the center of this runs the positive element, a carbon (non-metallic) rod that takes the place of the second metal.
Inside the container and around the rod is tightly packed a mixture of graphite, granulated carbon, and other materials; and this mixture—the electrolyte, corresponding to the acid solution of the zinc-copper cell—is moist, and must be. In both of these forms, a metal dissolves away and this chemical action yields an electric current.
The chemical action of the primary cell is irreversible.
What is meant by an “irreversible” chemical process? Let us fry an egg over a gas-jet; no cold, however intense, can unfry it, and no electric current, however strong, can restore it to its first estate.”
A reversible chemical change is one like the decomposition of water into two elements, hydrogen and oxygen. After this has been accomplished, the two elements will again unite to form water.
| || || |
| || |
| || || |
|Early flashlights benefited from the “dry” cell.|
The action of the so-called storage battery (or group of storage cells) is reversible; and “reversible battery” is a better though less popular term. “Storage battery” suggests that electric energy is stored in the apparatus; and such is not at all the case.
“Secondary battery” is satisfactory; it indicates the important fact that in its original form, this type of battery will not, like the primary battery, yield electric current. Only after current from some outside source has charged it, is the so-called storage battery prepared to function.
When Edison in 1900 began his hunt for the secret of a “good” storage battery, it was the battery of lead-sulphuric acid type that held the field. This battery, greatly improved since that time, is familiar in its three-cell form to drivers of motor-cars with internal-combustion motors.
The general principle of the storage-battery was known at least as far back as the early years of the nineteenth century, but the first important forward step was not taken until 1861, when Gaston Planté arranged plates of sheet lead in a solution of dilute sulphuric acid. Another advance was recorded in 1879, when Emile Faure brought out his “pasted-plate” type.
In 1881 Charles F. Brush (to whose arc-lighting system reference has already been introduced certain improvements, and with this stimulus the lead-sulphuric acid battery really entered its commercial stage in the United States.
The Planté type as first assembled has plates of sheet lead—pure metallic lead—and the solution (electrolyte) of dilute sulphuric acid. The plates have to be “formed”—that is, an electric current has to be passed through them repeatedly in alternate directions.
This results in producing lead monoxide at the surface of the plates. At the same time, through the action of the acid, the surface of the plates is covered with lead sulphate; and this, since it is practically insoluble, furnishes to the metal a protective covering that very largely prevents losses from local action.
| || || |
| || |
| || || |
|Planté cell was filled with dilute sulphuric acid.|
Now let the cells be charged—say, from a dynamo. It will then be found that whereas two plates were previously of the same material, they now have suffered a “sea-change”; at the surface of the positive (cathode) plate is lead peroxide, hard and of a reddish color; at the surface of the negative (anode) plate is metallic lead, spongy and gray.
The Faure type eliminates the long and costly process of “forming.” In this type, oxide of lead—either lead monoxide or red lead—in the fashion of paste is at the outset applied to the plates. Then when the battery is charged, the current transforms the surface of the positive plate into lead peroxide, the surface of the negative plate into metallic lead.
Briefly put, then, a charging current produces different effects in the positive and negative plates. If now the charging current is withdrawn and the battery is connected in circuit, the two plates act as two different metals do in the primary (or voltaic) cell: they set up a current.
This current is reverse in direction to the charging current. Hence the term “reversible battery.” It is chemical energy that is accumulated in such a battery (hence the term “accumulator,” used in Great Britain); but this chemical energy can be delivered in altered guise as electric energy.
This preliminary survey will perhaps help to make clear what Edison was trying to do and how radical were his departures in battery construction. It is said that back in the early ‘eighties at Menlo he made many experiments looking toward the improvement of the lead-sulphuric acid type, which even then he was inclined to regard as “intrinsically wrong.”
“This attitude kept him from seriously considering that type as an adjunct to his incandescent-lighting system. For incandescent lighting, a ton of coal, he said, was the best storage battery he knew.”*
* Storage batteries came to be used widely in connection with the larger lighting-systems and traction-lines. Current turned into batteries at slack times could be released during busy periods, to lighten the load on the generating plant.
| || || |
| || |
| || || |
|By 1900 storage battery construction allowed commercial applications such as this electric touring bus. Brown Brothers photo.|
When he started to hunt for a “good” battery, he was sure of two things: it was not to use lead, and it was to have an alkaline solution instead of an acid one. Otherwise, he could be certain of nothing.
Among the defects of which he was aware in the lead-sulphuric acid type were:
- the narrow restriction as to materials for containers;
- the tendency of the plates to buckle if in use when the electrolyte happened to be low;
- the dropping of fine particles to the bottom of a cell;
- the great weight, relative to electric capacity;
- likelihood of injury through overcharge, through extreme or complete discharge, or through remaining uncharged.
The sulphuric acid, too, gave out corrosive fumes, and it had the defect of its quality of attacking and decomposing practically everything with which it came in contact.
The battery he purposed to develop was to be used to supply motive power—chiefly for road vehicles, to some extent for street-railway cars. The job took about ten years of work by himself and a selected staff.
Over 10,000 experiments were made before any definitely encouraging results were won. Then iron and nickel promised the electric action that he sought. But this was only the beginning. He had a clue, indeed, but the way was long through the labyrinth.
Once it seemed that he had arrived, but this was a mistake; the journey had to be resumed. All told, about 50,000 experiments (the record of them filling over a hundred and fifty of the laboratory note-books) were demanded before the goal was achieved.
The complexities of this battery problem were tremendous. To J. W. Aylesworth, his chief chemist, Edison remarked, “In phonographic work we can use our ears and our eyes, aided with powerful microscopes; but in the battery our difficulties cannot be seen or heard, but must be observed by our mind’s eye !” There was need of all the old patience, all the old tireless persistence.
At midnight Edison’s carriage would be waiting to take him to “Glenmont”; but often it continued waiting until two or three in the morning, and at times it went back without him. From those earlier years of battery work—marked, like the incandescent-lamp period at Menlo, by long wakefulness, short sleep, and suppers at midnight—emerges the figure of Edison ensconced for a nap in a roll-top desk.
His head reposes on two or three volumes of Watts’ “Dictionary of Chemistry.” (Around the laboratory, a standing joke is that he is thus directly assimilating their contents.) He turns over, but without danger—he never tumbles. When he wakes, he wakes at once, evidently holding, with Secretary Chase, that the way to resumption is to resume.
One day, when work on the storage battery had been under way for over five months and more than 9,000 experiments had been made, Mallory found Edison sitting at a laboratory bench covered with test cells Nothing of promise had yet been reached.
Mallory expressed condolence: “Isn’t it a shame that with the tremendous amount of work you have done, you haven’t been able to get any results ?“ “Results !” Edison smilingly flashed back—”Why, man, I have gotten a lot of results. I know several thousand things that won’t work.”
It was not long before he hit upon something that did work.
| || || |
| || |
| || || |
|A determined Thomas Edison of 1901.|
The nickel and iron that he used were in chemical forms—nickel hydrate and iron oxide. At Silver Lake, about three miles from the West Orange establishment, he built works for the manufacture of these materials. At last he felt that commercial production of battery cells might be started.
The original battery was known s “Type E.” Though higher in first cost than a lead-sulphuric acid battery of corresponding output, it was well received and extensively purchased—not only because of Edison prestige and the newspaper announcements but also because results showed that it was cleaner, lighter, cheaper to maintain, and marked by the property—quite lacking in the lead-sulphuric acid battery and of decided value from the user’s viewpoint—of remaining uninjured when either overcharged or left uncharged.
The cells were made according to Edison’s rigorous standards of quality, with high-grade materials and uniform care.
After a while, however, evidence showed that for some reason or other the cells would now and again be of defective capacity. Assured of this, Edison saw that the logic of the situation was simply that as more cells were manufactured, more batteries would prove inferior.
Though he knew that if production were suspended, a large financial loss would be involved and the common impression would be that the battery was commercially a failure, he at once ordered that the factory shut down and announced that he would attempt to improve the old cell so as to give it increased capacity and a longer life.
Re-orders from satisfied purchasers were not accepted. It made no difference that “considerable pressure was at times brought to bear”—presumably by leading stockholders. As a contrast to the all-too-frequent spectacle of imperfect products forced upon the market by the dodges of advertising, this attitude on Edison’s part is, to say the least, refreshing.
A second course of experimenting was straightway in full blast. This resulted in the “Type A” battery, described by one of Edison’s laboratory assistants as “a finer battery than we ever expected.” “. . . Secrets,” declared this man, “have to be long-winded and roost high if they want to get away when the ‘Old Man’ goes hunting for them.”
Manufacture of the new type, begun in the summer of 1909, was being extended within a year.
For this vehicle battery, three sizes of cell were made. These were known as A-4, A-6, and A-8—the numerals indicating the number of positive plates that each contained. Both of the outside plates were negative, so that the cells had respectively five, seven, or nine negative plates.
The dimensions of the plates were identical for all cells; hence the one variation was in the thickness of the container or can, which was less or greater according to the number of plates. The cells were assembled in a wooden tray of light weight and strongly built.
In the standard assembled battery, the pounds per cell were:
- A-4, 14.21 pounds;
- A-6, 20.09 pounds;
- A-8, 26.15 pounds;
It was claimed that a vehicle battery when assembled weighed but little more than half as much as a lead-sulphuric acid battery of corresponding output.
| || || |
| || |
| || || |
|In 1910 this electric automobile used Edison’s new batteries for a 1000 mile endurance run.|
A cell might be divided into four component parts:
- (a) The electrolyte, a 21-per cent. solution of caustic potash (pure potassium hydrate) in distilled water;*
- (b) a group of positive plates connected in multiple with the positive terminal;
- (c) a group of negative plates, similarly connected with the negative terminal and intermeshed with the group of positive plates;
- (d) a container (or can) of nickel-plated sheet steel.
* (regarding the electrolyte) A small amount of lithium hydrate was also used. In November, 1923, the newspapers stated that Edison had purchased a spodumene mining lode in the Black Hills, Nebraska. Spodumene (or triphane) is a lithium-bearing mineral.
During the cycle of charge and discharge, the electrolyte remained unchanged with respect to specific gravity, conductivity, and the proportion of potash to water. Also, because the plates were immersed in a solution that was stable and non-injurious to metals, the cell might be left unused, either partially or wholly discharged, for a considerable time.
A positive plate was composed of a nickel-plated steel grid holding thirty tubes, each four and one-eighth inches long and with a diameter of a quarter-inch (or about that of the ordinary lead-pencil), arranged in two tiers of fifteen and packed with the positive active material, nickel hydrate.
It was lack of adequate electrical contact in these positive pockets that had caused Edison to be dissatisfied with “Type E,” and that led to experiments lasting about five years and costing more than a million dollars.
The tubes of “Type A” were of very thin sheet steel and perforated with minute holes, through which the electrolyte could seep. Into these tubes were packed, under a pressure of about four tons to the square inch, layers of nickel hydrate and of the material that finally solved the contact problem—nickel-flake.
The thinness of these layers may be judged from the fact that it required about seven hundred of them—about three hundred and fifty of each material—to fill a tube.
Nickel flake was made of pure nickel by an electroplating process* in which a hundred layers of copper and a hundred layers of nickel were deposited alternately upon a metal cylinder, then removed in sheet form and placed in a bath that dissolved away the copper. A handful of discs of this nickel flake would be as light as feathers. A bushel of them weighs only four and one-half pounds.
* Under date of 1924 the monograph “The Edison Alkaline Storage Battery” (National Education Association Joint Committee series, Monograph III) stated that according to the practice at that time, tubes were four and one-half inches long and about six hundred and thirty layers were packed under a pressure of 2,000 pounds to the square inch. In the electro-plating, one hundred and twenty-five films of each metal were deposited.
| || || |
| || |
| || || |
|Mr. Edison holds his new battery.|
|Cutaway drawing shows thoughtful and complete design of the new battery.|
When inserted in a tube, the discs made excellent contact with it and were conductors of current to and from the nickel hydrate. In order to prevent any expansion that might interfere with this contact, the tubes were made with a double-lapped spiral seam and over them were slipped metal rings.
A negative plate was composed of a grid holding twenty-four flat, rectangular pockets, perforated like the positive tubes and arranged eight in a row. The negative active material was an iron oxide quite like ordinary iron rust.
Sheets of perforated hard rubber insulated the two end (negative) plates from the walls of the container. Rods of it separated adjacent plates, and cross-pieces of it held the plates above the bottom of the can—only slightly, however, as the loss of active material was never more than trifling.
The container had its walls corrugated to some extent in order to provide the utmost rigidity with the least possible weight.
In a certain few respects this nickel-iron battery required somewhat particular care. The amount of electrolyte was relatively small. Hence the cells showed a greater tendency than did lead cells to heat suddenly through excessive current; and the electrolyte tended to evaporate.
Also, the small amount of electrolyte and the metal cans combined to make the cell more susceptible to cold than was the lead cell.
These matters were, however, regarded as of slight importance in comparison with the many advantages offered by the battery for electric-vehicle work—such as longer life, markedly lighter weight, lower maintenance cost, and more than double mileage per charge in road performance. In other words, the “good” storage battery that Edison sought seemed to have been found.
| || || |
| || |
| || || |
|At work in West Orange laboratory.|
The story of the Edison battery is one of insistent plodding—quite devoid of spectacular features such as were not lacking, for example, in the work on the incandescent lamp. As illustrative of Edison’s traits and methods, it has, however, much interest.
A co-worker during those ten years asserted, “If Edison’s experiments, investigations, and work on the storage battery were all that he had ever done, I should say that he was not only a notable inventor, but also a great man.”
The nickel-iron battery turned out to be peculiarly well adapted to a field not taken into account in its inventor’s original plans—the field of submarine service. Whatever might be thought of the possibilities of the submarine as an element in warfare (for great argument prevailed regarding this), it was generally agreed—and especially by those with experience—that for human sojourn a submarine’s interior left much to be desired, and particularly when the vessel was submerged.
When at the surface of the water, the submarine was driven by internal-combustion engines. The air inside it could then be kept pure. When submerged, the vessel was driven by electric motors.
Access of outside air was then, of course, impossible. A supply of chemically pure compressed air was carried in steel tanks, and a system—complicated at best—was tried for withdrawing the air from the vessel’s interior, to which it was later returned filtered, cooled, and with the oxygen restored to it.
These means did not, however, eliminate the poisonous fumes of the lead-sulphuric acid storage batteries.
The batteries supplied current for the motors that drove the propellers when the boat was submerged, and also for auxiliary motors used in managing torpedoes, in steering, in pumping.
When minute bubbles of gas—oxygen from the positive plates and hydrogen from the negative—rose to the surface of the electrolyte, passed through the open gas-vent of a cell, and floated away, each carried its tiny load of sulphuric acid, to be released in fumes when the bubble broke or was evaporated.
| || || |
| || |
| || || |
|U.S.S. Submarine Bonita was one of many being rapidly introduced into service before the Great War. Better batteries were necessary for their success.|
After a while—often without odor sufficient to attract attention—the air within the boat would become so tainted as to cause coughing and sore-throat among the crew. This was bound in time to affect the lungs and general health.
More serious yet, if salt water in any way came into contact with a battery, chlorine gas would be formed, offensive to smell and extremely harmful to those who breathed it. Lead-sulphuric acid batteries had also to be installed with elaborate provision and consequent expense, lead-lined rooms and lead-lined ventilating pipes being part of the specified equipment.
The Edison nickel-iron cell had a check-valve instead of an open vent; and in order for the bubbles to escape, pressure enough to lift the valve had to be developed within the cell. Even if the bubbles did escape, no harm could be done, because caustic potash was what the electrolyte of this battery held in solution, and potash is (as is well known) an excellent disinfectant.
Nevertheless, for submarine use, Edison provided the battery with a special device that completely removed potash from the gases. The Edison battery required no lead-lined rooms or other protective equipment. Uncommonly severe tests proclaimed its sturdiness.
Edison vouched for its long life. “Keep it clean,” he said to officials of the United States Navy, “and give it water and at the end of four years it will give its full capacity.” And when they queried with surprise, “Four years ?” he answered, “Yes. Four years, eight years; it will outwear the submarine itself.”
The Edison storage cell was also adapted to battery use with radio broadcast receiving-sets. For this purpose, the assemblies were of a special type. It was claimed that these batteries would outlast three to six radio storage batteries of any other make.