CHEMICAL EFFECTS OF ELECTRIC CURRENTS 22S 



cells in the battery may be obtained to operate the motor 

 which starts the gas engine, or to light the lamps. 



Storage batteries are quite expensive and require intel- 

 ligent care, else they are soon ruined. Owing to their special 

 construction a large current may be taken from them. Their 

 voltage is high, they offer less resistance, and hence they 

 can furnish larger currents. Some automobile-starting motors 

 may require for an instant as much as 250 amperes or more. 

 This is about 500 times the current consumed by the new 

 60-watt (Mazda B) tungsten lamp. The owner of a storage 

 battery should follow the instructions of the manufacturer 

 concerning its care. The following rules will prove helpful 

 in using the special directions furnished with the battery: 



Do not short-circuit the terminals of a storage battery. Do not 

 use an ammeter to test the cells. 



The battery should be kept free from dirt and foreign substances, 

 both solid and liquid. 



The battery must always be charged with direct current in the 

 right direction. 



Keep all connections clean and tight. 



Do not bring a flame near the battery during or immediately 

 after charging. 



The acid should be kept at the proper height above the top of 

 the plates. Use only pure water, melted ice, or fresh rain water, 

 and handle it in nonmetallic vessels. Do not add acid to the cells. 



The battery should be charged at the proper amperage and for 

 the proper length of time. 



The condition of the battery is indicated by the specific gravity 

 (density) of the solution, which is determined with a hydrometer 

 syringe. 



The acid of one make of battery has a specific gravity (density) 

 of 1.28 to 1.3 when charged, and 1.1 to 1.15 when fully discharged. 

 Other makes may differ. The specific gravity of the sulphuric-acid 

 solution is tested with the hydrometer (fig. 111). 



Test the battery each week. If the specific gravity (density) of 

 one cell continues much lower than the others, it may need the 

 attention of a battery expert. 



