The charging system performs several functions, which are as follows:

It recharges the battery after engine cranking or after the use of electrical accessories with the engine turned off.

It supplies all the electricity for the vehicle when the engine is running.

It must change output to meet different electrical loads.

It provides a voltage output that is slightly higher than battery voltage.

A typical charging circuit consists of the following:

BATTERY- provides current to energize or excite the alternator and assists in stabilizing initial alternator output.

ALTERNATOR or GENERATOR- uses mechanical (engine) power to produce electricity.

ALTERNATOR BELT- links the engine crankshaft pulley with alternator/ generator pulley to drive the alternator/ generator.

VOLTAGE REGULATOR- ammeter, voltmeter, or warning light to inform the operator of charging system condition.

STORAGE BATTERY
The storage battery is the heart of the charging circuit (fig. 2-2). It is an electrochemical device for producing and storing electricity. A vehicle battery has several important functions, which are as follows:

It must operate the starting motor, ignition system, electronic fuel injection system, and other electrical devices for the engine during engine cranking and starting.

It must supply ALL of the electrical power for the vehicle when the engine is not running.

It must help the charging system provide electricity when current demands are above the output limit of the charging system.

Figure 2-2.- Gross section of a typical storage battery.

It must act as a capacitor (voltage stabilizer) that smoothes current flow through the electrical system.

It must store energy (electricity) for extended periods.

The type of battery used in automotive, construction, and weight-handling equipment is a lead-acid cell-type battery. This type of battery produces direct current (dc) electricity that flows in only one direction. When the battery is discharging (current flowing out of the battery), it changes chemical energy into electrical energy, thereby, releasing stored energy. During charging (current flowing into the battery from the charging system), electrical energy is converted into chemical energy. The battery can then store energy until the vehicle requires it.