PRIMARY BATTERIES 



Approximate Energy Delivered per Unit Weight (Wh/oz.) 



If the endpoint can be reduced to 0-9 V per cell, the life of dry Leclanches is 

 usually appreciably increased ; if the discharge rate is relatively high it may 

 even be doubled. 



Reactivation of dry cells 



This subject has received some attention in recent years^'^ and may there- 

 fore be of interest. 



If batteries are exhausted by discharge, re-charging, or 'reactivation' as it is 

 commonly called, is not practicable. Under carefully controlled cycles of 

 charge and discharge with appropriate current consumption a measure of 

 reactivation is possible, but to obtain satisfactory results close control is 

 essential, and whilst attainable in the laboratory it cannot usually be effected 

 by the average user. Moreover if the proper conditions of reactivation are 

 not accurately maintained, battery life may be shortened rather than 

 lengthened. 



Vidor ^Kaliurn' cell 



These are generally similar to the cylindrical dry Leclanche ceil, but employ 

 mercuric oxide as depolarizer. They are stated to have a better shelf-life, 

 particularly for apparatus to be used under high temperature conditions. 

 It has been reported^ that they make excellent reference sources of e.m.f., 

 having a lower temperature coefficient (+17 parts per million per degree 

 Centigrade) even than the Weston's standard cell. 



Mai lory cells* 



In these cells the negative pole is zinc, the positive pole is mercuric oxide 

 and graphite and the electrolyte is potassium hydroxide. The whole is 

 enclosed in a steel case, giving good dimensional stability. In general, unlike 

 the dry Leclanche, the case is the positive pole. These cells are characterized 

 by an extremely constant voltage of about 1-3 during most of the discharge 

 period, very high relative discharge rates, good ratios of capacity to weight 

 and volume, and rather high cost. The makers also claim that the energy 

 output is independent of duty ratio. 



From the two dozen or so types of cell at present manufactured figures 

 are given for a large one (type RM 12), and intermediate size (type RM 1) 

 and a small one (type TR 112). Type RM 1 is shown in Plate 19.2. 



* Mallory Batteries Ltd., Dagenham, Essex. 



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