TRANSACTIONS OF SECTION G. 803 



Omitting the question of cost, tbe cbief points to be considered in connection 

 with accumulators are— the chemical action, the mechanical construction, and the 

 proper treatment of the cells when made. 



The theoretical value of lead peroxide is •4'44 grammes per ampere hour, or, 

 roun:hly, one pound is the equivaleut of 100 ampere hours. Presumiupr that the 

 positive and negative plates were identical, the value would be approximately 50 

 ampere hours for one pound of peroxide and spougj- lead. As a matter of iact, the 

 highest capacity plates yield only about seven ampere hours per pound of positive 

 and negative plates, or sixteen ampere hours per pound of peroxide and spongy 

 lead, due to the f\icts that a conducting frame of considerable weight has to be 

 employed, and to the impossibility in practical working of reducing the whole of 

 the peroxide. To obtain the best results for a given weight the frame mu.st be 

 reduced to a minimum consistent with the necessary strength and conductivity, 

 and the distribution of the jieroxide must be such as to admit of the perfect cu-cu- 

 lation of the electrolyte, and its penetration throughout the mass. 



The behaviour of cells under various conditions is most interesting, and from 

 the curves that can be plotted we can readily study the effects due to different 

 rates of charge and discharge, to the penetration and strength of the electrolyte, 

 and to the ratio of the weights of the positive and negative plates. 



There is a given rate of charge which is most suitable to each type of cell, 

 mainly due to the disposition of the active material, to its thickness, "and to the 

 method of its production, namely, whether it has been mechanically applied or 

 electrolytically produced. Most of the effects of varying rates of charge can be 

 ascertained from the resultant discharges, but discharge curves have nevertheless 

 characteristics of their own, which are to a great extent unconnected with the 

 conditions of charges. 



A series of curves was exhibited to the Section which gave the capacities of 

 .seven types of plates at present in use ; the yield was given in ampere hours per 

 pound of positive and negative plates, the weight of one positive and one iiegative 

 being taken in each instance ; the variation in capacity for high and low rates of 

 discharge was also shown. 



The striking point in these curves is the great variation existing in the various 

 types of plates now in use, but this can be explained to a great extent, for the 

 heavy solid plates, the active material of which is formed out of the plates them- 

 selves, must have a large reserve of weight to give them life, while pasted plates, 

 or plates with a large area, fall higher on the curve. One plate greatly exceeds all 

 the others in capacity, and this is due to the nature of the active material, which 

 permits the penetration of the electrolyte throughout the mass. 



Regarding the voltage of a discharging cell, this varies greatly, and is dependent 

 upon the rate of discharge, the strength of the electrolyte, and other causes. In 

 considering this question, it will not be out of place to draw attention to conditions 

 frequently met with in specifications for storage batteries. 



In some instances a given percentage in fall of voltage is allowed ; in others 

 the voltage per cell is fixed to a hundredth of a volt, above which limit it must 

 give the specified capacity. This type of specification is, as a rule, most unsatis- 

 factory, for at what point does our initial voltage start ? On open circuit ? 

 Immediately on closing the circuit, or five minutes afterwards ? Further, may 

 the cells stand for half a day after charging before the discharge is laken ? The 

 best way to meet this latter case is to take the first reading of voltage after the cell 

 has commenced discharging, and when 3 per cent, of the specified discharge 

 period has elapsed. 



The most satisfactory specification to all concerned is for the amperes to be 

 specified, and the time for which the discbarge is to be maintained, the voltage of 

 the complete battery at the end of tbe discharge being also given, the number 

 of cells being omitted ; this would require for a low voltage discharge per cell an 

 increased number of cells, but a decreased number of plates, or nice versa ; and 

 the author finds that this would not admit of the individual cells being worked to 

 too low a voltage, and that the purchaser would obtain exactly what he requires 

 at the lowest price, 



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