1885.J On Charging Secondary Batteries. 353 



10. Thinking that this remarkable diminution of internal resistance 

 might be due to the evolution of heat, I measured the temperature 

 with a delicate thermometer. 



Normal temperature of cell 12|° C. Current of discharge : — 



5 amperes .... No alteration of temperature perceived. 



10 ,, .... An exceedingly slight change. 



16 „ .... About 12}°. 



20 „ Barely 13°. 



The current in each case was kept on for 20 minutes, hence the 

 diminution is not due to heat. Since the internal resistance varies 

 in this way, I now always take the internal resistance with the same 

 current, viz.; 10 amperes. 



11. The capacity of these batteries certainly improves with age, 

 and up to the present time I have seen no sig'h of decay or deteriora- 

 tion. M. Plante informed me that, though in course of time the 

 peroxidised plate becomes very brittle, it is impossible to peroxidise 

 it completely through ; there always remains a metallic core to give 

 it strength. My experience of these plates confirms this. Up to the 

 present moment I have made no careful measurements of the 

 efficiency of my battery. I cannot do so without deranging the 

 lighting of my house, and I regard observations on single cells as 

 illusory. I put in about 240, and I take out about 200 ampere-hours 

 weekly, and I do not observe any change or fall in the electromotive 

 force. When the electromotive force of these cells falls, it falls 

 rapidly, indeed, almost suddenly. Occasionally one plate of a group 

 becomes inactive from undue local action, or from bad connexion 

 (shown by the colour). I remove this plate and put it in what I call a 

 "hospital" cell, where it is brought into order either by a greater 

 density of current or by reversal. Now that my plates have been in 

 use for some time they seem far less inclined to local action. In the 

 oldest cells there is no trace of local action. 



12. Reversing has a great beneficial action on a cell ; it not only 

 improves its capacity, bat it removes any cause of irregular working. 

 It is advisable to do this periodically. I have two extra cells, which 

 enables me to have two cells always under reversal by means of the 

 charging current. It takes from 1,000 to 1,200 ampere-hours to 

 reverse a cell in its present condition, so that at this time of year it 

 takes a month or more to complete the operation, and it will take a 

 year to reverse the whole battery. I have thus, up to the present 

 time, reversed 16 cells. 



