52 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 11, NO. 3 



cars were in ordinary running order when the measurements were 

 made. 



It is possible to show only two of the records in the present paper. 

 These have been chosen to illustrate the general character of the 

 curves which were obtained from a well-known 4-cylinder car equipped 

 with a 12-volt single unit starting system. Figure 1 shows the fluc- 

 tuations of current and voltage when the starter was in operation. 

 The initial starting current was about 125 amperes, but decreased 

 rapidly. The pulsating character of the current is due to the com- 

 pression in the successive cylinders. The minimum values of the 

 voltage correspond with the maximum values of the current. The 

 time scale in half seconds is shown at the top of the record. 



Fig. 2. — Starting of the engine, on second compression. A and A' indicate operation of 

 reverse current relay; B, release of starter pedal; C, charging current, engine speeding; D, 

 speed decreased; E, ignition cut-off. Interruptions in charging current caused by ignition 

 system. Same car as for Fig. 1. 



Figure 2 shows the characteristics of this particular car when the 

 ignition was on and the engine started. The initial starting current 

 was approximately the same as in figure 1 . The engine started on the 

 second compression. At the point marked A the current was zero 

 and the voltage at A' was approximately open circuit value. This 

 is believed to represent the operation of the reverse current relay. 

 An instant later the battery began to charge at a high rate — as in- 

 dicated by the current curve falling below the indices and the voltage 

 curve rising abruptly to a value in excess of the open circuit voltage. 

 At B the starter pedal was released and the current returned to the 

 normal charging value. A corresponding drop in voltage occurred 

 at the same time. The engine was racing at C, slowed down at D, 

 and the ignition was cut off at E. The interruptions seen in the charg- 

 ing current are due to the current flowing through the ignition coil 

 which is operated by the distributor. 



