Your Vehicle's Charging System

Team BlueStar Inspections

Your vehicle's charging system has two essential functions. It generates pressure, also known as voltage, and electrical power to run the vehicle's electrical systems while the engine is running. It also generates electrical current flow, known as amperage, to recharge and maintain the charge in the battery. The system consists of the alternator, voltage regulator, battery, and interconnecting wiring.

At low engine speeds, and with some electrical loads operating such as your air conditioning and blower fan, the battery may supply some of the electrical power the vehicle needs. At high engine speeds, the charging system handles all of the vehicle's electrical requirements. Once the vehicle's electrical needs are being met, the alternator sends current back to the battery in order to be able to recharge and maintain the charge of the battery.

The alternator operates when engine power transfers from the crankshaft pulley, through the serpentine drive belt, and into a pulley mounted on the alternator used to drive the alternator rotor. The alternator rotor spins inside the windings of a stator, the heart of the electrical system. The stator then generates an alternating current (AC) similar to the current in the electrical outlets in your home. Rectifier diodes then change the AC current into direct current (DC). This is how the alternator generates electricity for your vehicle.

The vehicle voltage regulator is designed to automatically maintain a steady output of voltage in a circuit. Your vehicle's electrical components are designed to operate within a range they can safely and optimally function. The voltage regulator is designed to keep these components in that range. A safe range falls between 13.8 and 14.3 volts while the vehicle is at idle with the lights and accessories turned off. An ideal voltage regulator setting is about 14.2 volts. The voltage regulator can be part of the computer or engine control unit (ECU), or it may be mounted inside the alternator. It controls the alternator's output current to prevent under-charging or over-charging of the battery.

The battery acts as a big cushion in the charging system, preventing high peak voltages or voltage surges. The battery helps prevent sudden and major changes in the charging system voltage. The battery provides momentary surges of power which can become necessary when systems are turned on. The battery also absorbs momentary excess amounts of power when systems are turned off.

Interconnected wiring attaches all of the charging system components together and provides an electrical return path, or ground, generally to the body of the vehicle. Longer lengths of wiring connecting accessories can reduce the amount of electrical power and pressure, or voltage, available at the accessory. For this reason, larger wire diameters are used in longer wiring runs to increase the performance by providing greater voltage.

Charging systems may also be designed with shorter lengths within the interconnecting wiring systems to help improve system performance. Poor connections in the wiring, also known as resistance to electrical current flow, are measured in terms of ohms. Resistance will disrupt the flow of electrical current and cause the charging system to function improperly. All power supply and ground connections should be inspected regularly. Poor ground connections are often an overlooked cause of low charging system output and alternator failure.

Each of your vehicle's charging system components rely heavily on one another. The failure or dysfunction of one component can affect the entire charging system. Have your charging system thoroughly inspected and tested by an ASE certified technician at least once per year.