The first authentic account of the new Edison storage battery was presented at the eighteenth annual meeting of the American Institute of Electrical Engineers, held in New York May 21. The paper was read by Mr, Arthur E. Kennelly, It is well known that the history of the storage cell is essentially that of the lead cell (tiscovered by Plante in 1860, in which lead peroxide is the depolarizing substance. An enormous amount of lauor has in the aggregate been expended upon the improvement of this cell in the hands of experimentalists, As a result of that labor the storage battery 'has at last become a recognized adjunct to direct-curent central stations; but it has limitations that seem to withstand further attempts toward improvement. Of late years hardly any success has been met with in the direction of reducing its weight for a given energy-storage capacity without detriment to endurance. and this weight is the great drawback of the storage battery in electric storage lJattery traction. and has been the principal obstacle to its advance in this direction for the past twenty years. In practice the storage energy per unit mass of the modern lead battery may be expressed as follows: The battery weighs from 124.5 pounds to 186.5 pounds per horse power hour at its terminals. While it is possible to increase the energy per unit mass uy making the electrodes very light. this has alwaYE been found to be followed by a very heavy deterioration. Many attempts have also been made to perfect storage cells of the alkaline zincate type. but the great difficulty of depositing zinc in coherent form from the solution. as well as the lack of a depolarizer that shall be insoluble in the electrolyte, has stood in the way of this cell's success. Mr. Edison set himself to the task of finding a cell which should possess the following advantages: absence of deterioration by work; large storage capacity per unit of mass; capability of being rapidly charged ami discharged; capability of withstanding careless treatment; and inexpensiveness. The negative pole or positive element of Mr. Edison's cell, corresponding to the zinc of a primary cell 0, the spongy lead of a secondary cell, is iron. The positive pole or negative element. corresponding to the carbon of R primary cell or lead peroxide of a secondary cell. is a superoxide of nickel, helieved to have the formula NiO,. The cell is. therefore, a nickeHron cell, a name which suggests the structural material--nickel-steel. The electrolyte is potash. viz., an aqueous solution containing 10 pel' cent to 40 per cent by weight, but preferably 20 per cent of potassium hydroxide. In practice with the ordinary storage battery the storage-energy per unit mass of the modern lead battery is from 4 to 6 watt hours per pound of battery; but the storoge capacity of the Edison cell per unit of total mass of steel is 14 watt hours per pound. Expressing the same statement in another way, the weight of the j)attery per unit of initial energy at the terminals is 53.3 pounds per E. H. P. hour. If the stored energy in the ordinary storage battery' availahle at the terminals were all expended in gravitational work, a battery could raise its own weight to a vertical distance of from 2 to 3 miles. With the Edison battery it could lift its own weight to a vertical distance of approximately 7 miles. The normal discharge period is 3% hours. The cell may be discharged at a relatively high rate in approximately one hour. Charging and discharging rates are alike. That is to say. the cell may be charged at the normal rate of 3V. hours, or it may be charged at a relatively liigh rate in one hour with no great detriment beyond a somewhat lower electrical efficiency. The positive and negative plates are mechanically alike and can Hcarcely he distinguished by the eye. They differ only in the c:hemical contents of their pockets. The construction of the battery is fully described in Mr. Kennelly's paper. which is puhlished in full in the current issue of the SCIM'LE.UE.NT. The cell is an oxygen-lift. Charging pulls the oxygen away from the iron and delivers it temporarily to the nickel. The condition is then stable, until the circuit of the cell is completed. The discharge then allows the oxygen to fall back from the nickel to the iron with the natural affinity of iron and oxygen. This action is very different from that whieh takcs place in the lead storage cell. In the new Edison cell the theoretical action of the potash solution is merely to provide the proper channel through which the oxygen iOlls may travel in one direction or the other--positive plate to negative plate in charge. and negative plate to positive plate in discharge. Secondly, the amount of solution needs only to ue sufficient to fulfill mechanical requirements. As regards cost it is believed that the new cells can be produced at a price per kilowatt hour not greater than the prevailing price of lead cells.
This article was originally published with the title "The New Edison Storage Battery" in SA Supplements 51, 1326supp, 338 (June 1901)