1942 - 1947 Chevrolet Shop Manual



12-4

the horseshoe magnet down over the wire the lines of force will be cut by the wire and in so doing a current is generated by the principle of electro magnetic induction. In this case we are moving the magnetic field so that the lines of force cut across the conductor. In both of the foregoing illustrations we were using mechanical movements; however, it is also possible to move the magnetic field electrically. This is the means used in producing the high tension current in the coil of our ignition system. THE CHEVROLET-DELCO BATTERY The storage battery, Fig. 8. may be considered a tank or reservoir in which eneregy from the gen-		When this electro-chemical action known as "charging" has been completed, it is only necessary to make a continuous, uninterrupted circuit between the positive and negative terminals of the battery, through the wiring system and electrical apparatus of the car, in order to produce electricity, and when used for a sufficient length of time, the battery is changed to its original or "discharged" condition. Electric current is generated in the battery in as full a sense as in an electric generator. From the foregoing it is obvious that the efficiency of the battery is in direct proportion to its state of charge: also that in order to obtain the maximum efficiency from the battery, whatever amount of current is withdrawn from or generated by the battery must be compensated for by running the generator long enough to restore the battery plates to the condition known as "charged." The construction of a storage battery is extremely simple. A battery possesses three compartments or cells. Within each cell are two elements, one positive ( + ), and the other negative (-). Each element consists of a number of plates called "grids," the openings of which are filled with a lead paste. Each group of plates is connected together and the positive are separated from the negative group by porous separators between each plate. The liquid in which these plates are immersed is called electrolyte (sulphuric acid and water). When the battery is being charged, acid is driven from combination in the plates and causes the specific gravity of the solution to rise. When the battery discharges, the acid combines with the paste material of the plates, forming a chemical compound, and the specific gravity falls, until in the case of a completely discharged battery, the solution is practically all distilled water. The battery, while undergoing a charge, emits gases, during which the battery is said to be "gassing." It also has a tendency to heat if the charging rate is abnormally high; therefore, it is essential that distilled water be added from time to time to replace the loss in water due to this "gassing" (which results from the decomposition of the water). At the top of each cell is a vent or opening accessible by unscrewing the vent or cell cap. Immediately upon receipt of a battery or a new automobile, the battery should be inspected. All cell caps should be removed and the level of the solution in each cell checked. Due to the location of the battery under the hood on passenger cars, it is most important that the water level be checked more frequently than

	READING FOR FULLY CHARGED BATTERY SHOULD BE BETWEEN 1275 AND 1300
Fig. 8-Testing Specific Gravity of Battery erator may be accumulated and stored until it is required. Since the performance of the electrical equipment depends to a great extent on the condition of the storage battery, its function should be thoroughly understood. The battery, popularly referred to as "storage battery," gives rise to a false conception of the true nature of the battery. The battery is in reality an electro-chemical apparatus. Electricity is not actually stored in the battery until needed but is caused to flow into the battery and out by means of two wires attached to it. None of the electricity stays there; certain changes merely take place within the battery itself. Charging a battery by causing electric current to flow through it sets up a certain electrochemical action between the positive and negative plates in the presence of the battery fluid or electrolyte.