BATTERIES 



0-1 



3A567891 2 3 



Energy delivered per unit volume 



Figure 19.4 



6 7 8 910 



Wh/in!^ 



• -• — Mallory cells 



Cylindrical dry Leclanche cells 



-Layer Leclanche cells*. 



Mill 



• — — Ni-Fe celts-** 

 Silver-zinc cells 



-Lead-acid cells 



I Mil l 



I I I I M I I I 



I I I I 



01 



1 2 A 6 8 10 



Approximate range of 

 capacities of types of cells 



Figure 19.5 



6 8 100 2 U 



Ampere-hours at 

 lOh rate 



SECONDARY CELLS 



The lead-acid cell or ''accumulator'' 



These are too well known to require description. They have a steady voltage 

 of 2 during the greater part of the discharge period. On first connecting the 

 load to a freshly charged cell the voltage may be 2-2, and discharge should 

 be stopped when the voltage has fallen to 1-8. Accumulators can be quickly 

 damaged if proper attention is not paid to their maintenance, and at best 

 their life is about 5 years. To investigate their storage properties we take 

 four examples, all of which might be found supplying electronic equipment : 



Battery A — a 1 2 V car battery 



Battery B — a 6 V motor cycle battery 



Battery C — a glass encased 'laboratory' type of cell 



Battery D — a small celluloid-encased cell. 



These are shown in Plate 19.4, and details are : 



288 



