Electrical Devices and How They Work 



Secondary Cells; Storage Batteries— II 



Accumulators are cells of battery that will receive a charge of electricity 

 and keep it stored until it is released through mains for power and liglit 



By Peter J. M. Clute, B. E. 



I 



N the primary cell, electric current is 

 produced by the decomposition of the 

 electrolytic solution and the consump- 



In other words, 



Projecting ormfor 

 connecting plates 



Positive lead grid 

 of a storage cell 



tion of a zinc electrode 

 the varying natural 

 potentials of two sub- 

 stances, such as zinc 

 and copper or zinc and 

 carbon, constitute the 

 original impulse to a 

 succession of reactions 

 whereby chemical 

 energy is transformed 

 into continuous elec- 

 trical energy. On the 

 other hand, in the 

 secondary, or storage, 

 battery, electric cur- 

 rent is generated by a 

 somewhat similar 

 chemical reaction, 

 originated, however, 

 by chemical changes, produced by an 

 electric current passed through the cell at 

 the start of operations. This operation is 

 termed the charging of the cell. 



Such cells are called secondary cells be- 

 cause their action is dependent upon the 

 effects of the energy impressed upon them 

 by a primary electrical source. They are 

 designated as storage batteries because, 

 apparently, a quantity of electrical energy 

 is stored in them in the form of current, to 

 be delivered, also in the form of current, 

 when the battery is connected as a source 

 of electricity. 



Storage cells of all descriptions are 

 charged from D. C. service mains, or 

 from special charging generators. The 

 current may be regulated to the required 

 rating by suitable resistance, usually 

 through special switchboards, designed to 

 meet the requirements of charging. If 

 the only available current supply is 

 alternating, it can be transformed into 

 direct current by means of a rectifier, or a 



motor-generator set. The secondary cell 

 is capable of being recharged after ex- 

 haustion by passing an electric current 

 through it in a direction opposite to that 

 of the current on discharge. This dif- 

 ference constitutes the principal ad- 

 vantage of the storage battery over the 

 primary cell. 



The typical storage cell is the lead-lead 

 couple in an acid electrolyte. There are, 

 however, other varieties of such cells, all 

 of them more or less experimental in 

 character. These may be designated as 

 lead-copper, lead-zinc, alkaline-zincate, 

 etc., all using corrosive electrolytes. In 

 addition to these, and in a class by itself, 

 is the Edison nickel-iron cell, using an 

 alkaline and non-corrosive electrolyte. 



The commercial storage cell consists of 

 an even number of positive plates and an 

 odd number of negative plates, immersed 

 in a dilute electrolyte (generally sulfuric 

 acid) contained in a jar or box of non- 

 conducting material. The plates are ar- 

 ranged alternately positive and negative, 

 and are cast with 



Negative plote 



Positive 

 Plate 



Positive plates of per- 

 forated steel tubes 



a projecting arm 

 as shown in Fig. 1, 

 so that all posi- 

 tives may be con- 

 nected by a single 

 stud, and all nega- 

 tives similarly 

 united — each such 

 unit of several 

 plates being one 

 element of the cell. 

 The positive ter- 

 minal at which 

 the charging cur- 

 rent enters the 

 cell, passing to all 

 positive plates, 

 and at which the 



current leaves the cell on discharge, is 

 called the anode. Similarly, the negative 



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