introduction to your electrical system
 

Electricity is Like Water (but don't mix them)

Comparing water flow with electrical flow is without a doubt the easiest way to explain volts (voltage), amps (amperage) and Ohms (resistance). This makes a good comparison because we are using something that can be seen to describe something invisible.

Movement of electricity through a circuit is much the same as the movement of water through a pipe. Just as gallons of water per minute is the rate of water flow, amperage (amps) is the measure of electrical flow (current). In the automotive electrical system the alternator plays the important role of replenishing the amps or current drawn from the battery. The size of the battery, coupled with the output of the alternator, determines the amount of current (amps) available to operate the various electrical systems.

There's a lot in common between a water tower and a storage battery in that they both provide pressure. A water tower supplies water pressure while a battery is the source of electrical pressure. The voltage regulator maintains the desired voltage to the battery. It is voltage that pushes electricity through the wires in a circuit just as pressure pushes water through pipes.

Ohms is the resistance. for example, the smaller the pipe the more pressure is required to force water through it, hence the greater the resistance. Therefore a larger pipe is needed to reduce resistance and when this is accomplished volume is increased. The same can be said for an electrical circuit. for example one would not use 16AWG wire from a battery to the starter because it offers too much resistance. The wire would end up being burnt because there is too much force (volts) and too many amps drawn by the starter.   Rather a correct choice would be to use 4AWG or larger cable for this application. The same is true of other electrical circuits. We cannot stress enough the importance of using the correct size wire for any given circuit. It's important to know how much current (amps) the circuit will use.



Introduction to Charging System

Alternator

An alternator in its simplest terms is a small rotating electro-magnet inside a fixed coil of wire called a stator. When the electro-magnet rotates, it produces a field in the stator which in turn produces alternating current.

In the early 1960's increased demands for electrical current in automobiles made it necessary to develop a
charging system that would be adequate to meet theses requirements. The existing charging system was made
up of a DC generator, a voltage regulator and a battery. The DC generator proved to be inadequate and the
industry responded with the development of what we know today as the Lundell alternator, or AC generator. This
system has proven reliable and certainly adequate for today's modern vehicles which require huge amounts
of amperage to drive their electrical systems. With the advent of computers, electric fuel pumps, stereos and a myriad of other power-consuming accessories, the alternator has proven its ability to provide reliable electrical energy.

The alternator provides an alternating current to a rectifier assembly which in turn converts that alternating current (AC) to direct current (DC) which the battery and the car's electrical system can use. In addition, the alternator is controlled by electronic circuits which carefully regulate the DC current flowing into the rotor (field), thereby regulating the output. If the regulator were not present, the battery would receive an overcharge (25 Volts or higher) and subsequently be destroyed over a period of time. It must be noted that another direct link in alternator output is engine speed which, of course, translate to rotor (alternator) speed. An alternator puts out less at idle than at highway speed. The efficiency of modern alternators is greatly enhanced over earlier models.
After the alternator has reached maximum output, a drain begins in the reserve stored in the battery. The battery and the alternator work as a team. The charging system is only as good as the weakest link -- battery, alternator or cables.

Wire and Cables

10 AWG and smaller is usually referred to as primary wire. 8 AWG and larger is usually referred to as cable. The larger the number, the smaller the wire size.

Batteries

The primary use for a battery is to provide a source of power for starting and for electrical demands which temporarily exceed the alternator output. The battery also acts as a stabilizer for the voltage in the entire electrical system. Acting as a reservoir, large amounts of DC current can be removed quickly when starting and then replaced slowly by the alternator. Because a battery should be able to smooth out short term high or low voltage, the battery must be in good serviceable condition before testing the charging and cranking systems of the vehicle. If a battery is discharged, the cranking circuit, charging unit, and other sensitive electronic components could test as being defective because the battery may drop below voltage specifications. Remember, it is imperative to test a vehicle battery and check for adequate voltage before testing any of the charging functions, cranking functions or electronic management functions.

Voltage Regulators

Voltage regulators were at one time merely mechanical switches electro magnetically controlled to regulate the proper amount of voltage flowing to the battery. Today's modern voltage regulators are frequently mounted on the inside of the alternator.  Units with one-wire regulators are very popular because they are easy to install. Circuitry is built into the regulator that allows it to self energize.  A volt or amp gauge can be installed to show the true condition of the battery. The ground terminal of the gauge should be tightly grounded. The positive terminal can be attached to any point in the charging path (from alternator battery post to battery). The most accurate results can be obtained by attaching to the battery positive post.