Automotive Electrical Basics

One of the biggest changes in automobiles from the earliest models to today's complex cars and trucks has been increasing reliance on electrical systems and features. Every car has a battery, and the systems powered by it are extremely important to the safety, comfort, and efficiency of the vehicle and its passengers.

Batteries

Most cars feature a rechargeable lead-acid battery to power the electrical system. These batteries contain plates of lead oxide suspended in an electrolyte solution where a chemical reaction causes the storage and release of electricity. Car batteries are charged by the power of the engine during driving and can provide power when the engine is not running for a time. Most car batteries last between five and ten years before they will no longer hold a sufficient charge and must be replaced.
In the case of hybrid electric vehicles, additional rechargeable batteries are connected directly to the vehicle's drive mechanism, storing energy during braking and coasting and then actually powering the driveshaft under certain conditions, allowing for maximum fuel efficiency.

Driving

The simple act of driving would be impossible without help from a car's electrical system. The engine starter is powered by the battery and is required to begin the combustion cycle which will then become self-sustaining. Even then, as the engine runs, the alternator and spark plugs deliver precision sparks to produce the combustion that powers the car.
Most modern cars and trucks also feature electronic fuel injection and any number of electronic sensors to indicate and regulate engine performance. This includes systems like variable valve timing, in which the engine';s timing is adjusted to provide extra power when it is most needed or drive-on-demand systems that effectively shut down an unneeded portion of an engine to reduce overall fuel consumption.

Safety

Electronic systems also figure prominently in vehicle safety. Airbags are deployed when electronic sensors transmit a signal that an accident is occurring in a fraction of a second. Likewise, anti-lock braking systems use sensors to detect slipping and skidding, and then employ an electric motor to pulse the brakes, hopefully bringing the vehicle to a safe stop. Even a vehicle's headlights and directional turn signals are powered by the electrical system.
More complex electronic safety systems are becoming more common. These include features like rear-view cameras that display the space behind the vehicle on an in-dash screen to the driver, as well as automatic headlights and windshield wipers that provide a driver with increased visibility by detecting the environmental conditions.

Diagnostics

One relatively new use of a car's electrical system is the integration of central processing units (CPUs) into most cars. These computer chips monitor data from sensors all over the vehicle and, in the case of a malfunction, can provide a technician with information about the location and source of the problem. Some cars will display these error codes on their clocks or odometers, allowing drivers to determine the nature of a problem indicated by warning lights or a noticeable change in performance.
Trip data information is also displayed by CPUs, allowing drivers to monitor their fuel economy, and keep track of multiple vehicle systems on a single digital gauge.

Comfort and Entertainment

Finally, the electrical systems of many cars are largely devoted to features that increase vehicle comfort and provide entertainment options. Radios, CD players, MP3 players, speakers, and even DVD players or televisions are all powered by a vehicle's electrical system. In some cases, these specialty features require the use of a secondary battery so that they do not draw power from the same source as essential vehicle systems.
Convenience features, such as power windows, power door locks, automatically adjustable seats, and power convertible tops or sun roofs also rely on the availability of electrical power. Related electrical systems include heated seats, air conditioning, compasses, decorative interior and exterior lighting, passive restraint seat belts, and integrated GPS or cell phone hookups.

References

• Understanding Your Import Car's Electrical System
• Automobile Electrical System

Resources

• Your Car's Electrical System