SECONDARY CELLS 



From the above we can construct the following : 



Nickel-iron-cadmium cells or 'Ni-Fe' cells* 



These are steel-cased cells whose electrodes are steel plates in the form of a 

 matrix of perforated pockets. These pockets contain, for the negative plates, 

 a preparation of cadmium and iron, and for the negative plates, nickel 

 hydroxide. The electrolyte is an aqueous solution of hydroxide. The voltage 

 of discharge at normal rates is 1-2. Advantages of the Ni-Fe cell over the 

 lead acid cell are absence of corrosive fumes and spray (an important point 

 with delicate apparatus), a very long life (15-20 years), virtual indestructi- 

 bility — both electrical and mechanical (the cells may be overcharged, left 

 uncharged, short-circuited, all without harm) — and ability to hold charge for 

 long periods. These points should be borne in mind when looking at the 

 performance figures which show the Ni-Fe cell in a somewhat unfavourable 

 light compared with the other secondary cells. We take two examples from 

 the manufacturers' catalogue of portable batteries mounted in hardwood 

 crates for general laboratory use. 



* NIFE Batteries, Redditch. 



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