5°4 



ENGINEERING ON THE FARM 



Approximate Temperatures at Which a Lead 

 Plate Storage Battery Will Freeze 



Specific Gravity 



1. 12 



I.l6 



1. 21 



I .26 



I. 28-1. 30. 



State of Charge 





Discharged 

 One-fourth charged 

 One-half charged 

 Three-fourths charged 

 Fully charged 



Freezing Point 



25° F. (above) 

 o° 

 20 below o° 

 50 below o° 

 Will not freeze 



Hydrometers are callibrated to read correctly at 70 F. 

 If the temperature is above or below this point, the observer 

 should correct the reading .001 for each Ithree degrees of 

 variation, subtracting correction when the temperature is 

 above 70 and adding when it is below. 



One of the later steps in storage-battery construction, 

 known as the Edison storage cell, involves the use of nickel 

 and iron in a nickel-plated container, caustic potash being 

 used in the electrolyte. The cell delivers a pressure of only 

 about one volt. Its activity is very much reduced in low 

 temperature. The objections of excessive weight and acid 

 fumes of the lead cell are, however, very effectively eliminated. 



Positive wire 



=5 



•— o- 



tj — ir ^s 



Main fine, direct current Negative tvire 



Lamps 



'yvitct? 



Fuse 



Fig. 396. Method of connecting to an outside source of current to be used 

 for charging a storage battery. Number of lamps used will be determined 

 by amperage necessary to charge battery properly 



It is essential that all battery connections be clean and 

 tight. A very small quantity of foreign matter prevents 



