Charging System

The function of the automobile battery is to supply a sufficient amount of electricity to the automobile's electrical components such as the starter motor, headlights and wipers. However, The battery is limited in its capacity and is not capable of providing, On a continuing basis, All the power required by the automobile.

It is necessary, Therefore, For the battery to always be fully charged in order for it to supply the necessary amount of electricity at the required time to each of the electrical components. Consequently, The automobile requires a charging system to produce electricity and keep the battery charged.

The charging system produced electricity to both re-charge the battery and to supply the electrical components with the amount of electricity required while the automobiles engine is in operation.

Most automobiles are equipped with alternating current alternators as they are better than direct current dynamos in terms of electric power generating performance and durability.

Since the automobile requires direct current, The alternating current produced by the alternator is rectified (Converted to direct current) just before output.

Basic of Charging System

The charging system includes the alternator, voltage regulator which is often a part of the alternator itself), the battery, and the indicator gauge or warning light on the dash (See Alternator, Battery and Voltage Regulator). The charging system's job is to generate enough current to keep the battery fully charged, and to satisfy the demands of the ignition and electrical systems. The voltage regulator senses the demands on the electrical system, and controls alternator output so sufficient current is produced. A loose V-belt, or a defective alternator or voltage regulator can cause the dash warning light to glow red (or the amp gauge to show and steady discharge). If the problem isn't corrected, the battery will run down and eventually go dead.

The electrical system in an automobile is said to be a 12 volt system, but this is slightly misleading. The charging system in most cars will generally produce a voltage between 13.5 and 14.4 volts while the engine is running. It has to generate more voltage than the battery's rated voltage to overcome the internal resistance of the battery. This may seem strange, but the current needed to recharge the battery would not flow at all if the charging system's output voltage was the same as the battery voltage. A greater difference of potential (voltage) between the battery's voltage and the alternator's output voltage will provide a faster charging rate.

    As long as the engine is running, all of the power for the accessories is delivered by the alternator. The battery is actually a load on the charging system. The only time that the battery would supply power with the engine running is when the current capacity of the alternator is exceeded or when engine is at a very low idle.

A basic alternator has 2 main electrical components. The rotor and the stator. The rotor is the part of the alternator that is spun by the drive belt. There are a group of electrical field coils mounted on the rotor. The stator is the group of stationary coils that line the perimeter of the inside of the alternator case. When current (supplied by the voltage regulator - to be explained later) is flowing in the rotor's coils, they induce current flow in the stationary coils. The induced current (and voltage) is an AC current. To convert this to DC, the current is passed through a bridge rectifier.

Rotor and Stator Winding

Stator and Rotor in Action:

In the following diagram, you can see three crudely drawn sets of rotors and stators. In the leftmost diagram (marked 'A'), you can see the rotor's coil approaching the stator coil. As the rotor coil approaches the stator coil, it induces current flow in the stator coils. This causes an increase in output voltage. As it approaches the position where the coils' centers are aligned ('B'), there is no induced current. When the coils move away from each other ('C') the induced current flows in the opposite direction and the generated voltage is negative.

Rectifying

You should also realize that there are 3 different groups of stator coils in an alternator (not shown in diagrams). The rectification is much like the simple transformer shown above but in the place of a single transformer winding there are 3 windings. It also uses 6 diodes instead of 4.

Flowing Current In and Out of the Battery

3 Phase:
  
The following diagram shows the 3 different phases from the 3 groups of stator windings. The three phases of AC are shown in three different colors. The next set of lines shows the rectified waveforms overlapped. The bottom waveform (white line) is what the rectified voltage would actually look like if viewed on an oscilloscope. Connecting the battery to the alternator will smooth the white line even more.

Three Phase Stator Winding

The following is a generic schematic showing the stator windings and the bridge rectifier. You also see a diode trio. the diode trio takes part of the output and sends it to the voltage regulator. The output diodes are the rectifiers that rectify the AC and supply power to your electrical accessories.
For an alternator to produce electrical current, there needs to be some excitation current flowing in the rotor windings. Since the rotor is spinning, you can't just connect a couple of wires to it (cause they'd just be twisted off. To make the electrical connection, slip rings and brushes are used. The slip rings are fixed to the shaft of the rotor. The brushes are fixed to the stationary part of the alternator. The brushes, which are generally made of carbon, are spring loaded to keep constant pressure on the slip rings as the brushes wear down. The following diagram shows the general location of the rotor and the associated parts.

Functions of Brush and Slip Ring

Magnetic Switch

Magnetic Switch

The magnetic switch (Also referred to as a Solenoid) consists of a hold-in coil, Pull-in coil, A return Spring, A plunger and other components. It is activated by the magnetic forces generated in the coils and carries out the following two functions:

• It pushes the pinion gear so that it meshes with the ring gear.

• It serves as a main switch or relay, Allowing heavy current to pass from the battery to the starter motor.  

Field Coils

Field Coils

The electrical current from the magnetic switch flows through the field coils, Which generate the magnetic field required to rotate the armature.

Brushes

Carbon Brush

The brushes, pressed against the segments of the armature commutator by the brush springs, Allow the current to pass from the field coils to the armature.

NOTE

Weakened brush springs or worn brushes may lead to insufficient electrical contact 
between the brushes and the segments of the commutator. The resulting excessive 

electrical resistance at the contact points will reduce the supply of current to 

the motor, Impeding torque build-up.

Armature

 
The armature, The revolving component of the motor, Consists of the armature core, Armature coils, Commutator, etc. It revolves as a result of the interaction between the magnetic fields generated by the armature coils and the field coils.

Starter Clutch

Starter Clutch

The starter motor must crank the engine until the engine fires and starts to run on its own. Once the engine has started, However, It would force the starter motor to rotate at a much higher speed than that for which it is designed, Which would damage the starter motor. The starter clutch is a one-way clutch which protects the starter motor from this. Although the construction of the starter clutch used for the conventional type starter motor is somewhat different from that used for the reduction type starter motor, The principle and operation of each is essentially the same.
Although the construction of the starter clutch used for the conventional type starter motor is somewhat different from that used for the reduction type starter motor, The principle and operation of each is essentially the same.

Starter Clutch During Cranking

Starter Clutch During Cranking

 The rotating armature tries to force the clutch housing to which it is splined, To rotate faster than the inner race, Which is combined with the pinion gear. The clutch rollers are therefore forced to roll toward the narrower sections between the clutch housing and inner race until they jam between the clutch housing and the inner race. As a result, The rollers transfer the rotational movement of the clutch housing to the inner race and thence to the pinion gear.

Starter Clutch after Engine is Started

Once the engine has started, Its torque tries to force the inner race to rotate faster than the clutch housing. The clutch rollers therefore roll against the springs towards the wider sections inside the housing. As a result, The clutch housing and the inner race disengage to prevent the starter clutch from transmitting the engine torque from the pinion gear to the starter motor.

Solenoid

Internal Solenoid Operation

Solenoids act as electric to mechanical energy converters, taking an electrical signal and converting it to work. The operation is based upon the reaction of a moving element, the armature or plunger, in response to a magnetic field developed by an electrical conductor, usually a winding. Solenoids can be configured to operate in either Direct Current (DC), or Alternating Current (AC). Solenoids are electromechanical actuating devices found in many types of applications.

Solenoid External and Internal Parts

The solenoid switches is the part of automobile which relays a large electric current to the starter motor. The system converts electrical energy from the batteries into mechanical energy to turn the engine over. It is mounted on the starting motor and forms the major component of the starting system. The coils inside the solenoid are energized by electricity, they create a magnetic field which attracts and pulls a plunger. Attached to one end of this plunger is a shift lever. The lever is connected to the drive pinion and clutch assembly of the starter motor.
The solenoid receives a large electric current from the car battery and a small electric current from the ignition switch. As the ignition switch is turned, a small electric current is sent to the starter solenoid. The pair of heavy contacts closes, relaying the a large electric current to the starter motor, which in turn sets the engine in motion.
Once the engine starts, the key-operated switch is turned, a spring in the solenoid assembly pulls the pinion gear away from the mesh, and the starter motor stops. The starter's pinion is clutched to its driveshaft through an overrunning sprag clutch which allows the pinion to transmit drive in only single direction. In this manner, drive is transmitted through the pinion to the flywheel ring gear.

Armature

Starter Motor Armature

Armature may be referred to one of the two principal electrical components of an electromechanical machine - a motor or generator, but may also mean the pole piece of a permanent magnet or electromagnet, or the moving iron part of a solenoid or relay.

The role of the component is simply to create a magnetic field (magnetic flux) for the armature to interact with, so this component can comprise either permanent magnets, or electromagnets formed by a conducting coil. The armature, in contrast carries current so in a form of conductor or a conductive coil, oriented normal to both the field and to the direction of motion, torque (rotating machine), or force (linear machine).

The role of the armature can be described in two folds:

To carry current crossing the field, thus creating shaft torque (in a rotating machine) or force (in a linear machine)
To generate an electromotive force ("EMF").

An electromotive force ("EMF") is created by the relative motion of the armature and the field. When the machine work as a motor, the EMF produces a resistance for the armature current, and the armature converts the electric power to mechanical torque. The generated load is transfered through the shaft. In the induction generators, these distinction are totally blurred, since the generated power is drawn from the stator, normally be considered the field.

Starter Motor

The starter motor is a powerful electric motor, with a small gear (pinion) attached to the end. When activated, the gear is meshed with a larger gear (ring), which is attached to the engine. The starter motor then spins the engine over so that the piston can draw in a fuel/ air mixture, which is then ignited to start the engine. When the engine starts to spin faster than the starter, a device called an overrunning clutch (bendix drive) automatically disengages the starter gear from the engine gear.

Starter Motor Planetary Type

 The starting system converts electrical energy from the batteries into mechanical energy to turn the engine over. A malfunction within the starting system will make it difficult to get the engine running.

In order to properly service the starting system, you need to understand how it operates. The starting system has five main components: the ignition switch or start button, a neutral safety switch (an option on some vehicles), the starter solenoid, the starter motor, and the batteries.

When the key is turned in the ignition switch to the start position, or the start button is pushed, electricity flows from the batteries to the starter solenoid.

Some vehicles are equipped with a neutral safety switch. If the vehicle is in gear when the key is turned, the neutral safety switch blocks the signal to the batteries, so the engine doesn't start cranking. Otherwise, the vehicle could jump forward or backward when the key is turned.

The starter solenoid is an electromagnetic switch mounted on the starter motor. When coils inside the solenoid are energized by electricity, they create a magnetic field which attracts and pulls a plunger. Attached to one end of this plunger is a shift lever. The lever is connected to the drive pinion and clutch assembly of the starter motor.

Operation of Starting System

Ignition Switch in "START" Position

Ignition Switch Start Position

When the ignition switch has been turned to the START position, Terminal 50 passes electrical current from the battery to the hold-in and pull-in coils. From the pull-in coil, the current then flows to the field coils and armature coils via Terminal C.
At this point, the voltage drop across the pull-in coil keeps the amount of electrical current flowing through the motor components (field coils and armature) small, so the motor rotates at a lower speed. At the same time, magnetic fields generated by the hold-in and pull-in coils pull the plunger toward the right against the return spring. This movement causes the pinion gear to move toward the left, via the drive lever, and mesh with the ring gear. The low starter motor speed at this stage means that the gears mesh smoothly.
The screw splines help the pinion and ring gears to mesh smoothly.

PINION AND RING GEARS ENGAGED

Pinion and Ring Gears Mesh

 When the magnetic switch and the screw splines have pushed the pinion gear to the position where it meshes completely with the ring gear, the contact plate attached to the end of the plunger turns the main switch on by short circuiting the connection between Terminals 30 and C. The resulting connection causes a heavier current to pass through the starter motor, which causes the motor to rotate with a greater torque. The screw splines help the pinion gear mesh more securely with the ring gear. At the same time, the voltage levels at both ends of the pull-in coil. The plunger is therefore held in position only by the magnetic force exerted by the hold-in coil.

IGNITION SWITCH "ON" POSITION

Ignition Switch On Position

Turning the ignition switch back to ON position from START cuts off the voltage being applied to Terminal 50. The main switch remains closed, however, so some current flows from Terminal C to the hold-in coil in the same direction as when the ignition switch is in the START position, it generates a magnetic force which pulls the plunger. In the pull-in coil, on the other hand, current flows in the opposites direction, generating a magnetic force which tries to return the plunger to its original position.
The magnetic fields set up by these two coils cancel each other out, so the plunger is pulled backward by the return spring. Therefore, the heavy current which has been supplied to the motor is cut off and the plunger disengages the pinion gear from the ring gear at about the same time.

Starting System

DESCRIPTION

Since the engine is not capable of starting by itself, it requires external power to crank it and help it start. Among the various means available, automobiles now use an electric motor that has been combined with a magnetic switch that shifts a rotating pinion gear into and out of mesh with the ring gear on the circumference of the engine flywheel.
The starter motor must generate a large torque from the limited amount of power available from the battery. At the same time, it should be light and compact. For these reasons, a DC (direct current) series motor is used.
The engine is not completely started until it can continuously repeat its operational cycle of intake, compression, combustion, and exhaust strokes on its own. The first step for starting the engine, then, is to crank the engine and induce the initial combustion cycle. The starter motor must therefore be at least capable of cranking the engine at the minimum rotational speed that is required to induce initial combustion.

Starter Motor

The starter motor is a small but powerful electric motor that delivers a high degree of power for a short period of time. When the starter motor is energized it engages the flywheel ring gear and produces torque, which turns the flywheel and cranks the engine.
When the driver releases the ignition switch from the start position to the run position, the solenoid is deactivated. Its internal return springs cause the drive pinion to be pulled out of mesh with the flywheel, and the starter motor stops.

IGNITION SWITCH

Universal Ignition Switch

 The ignition switch allows the driver to distribute electrical current to where it is needed. There are generally 5 key switch positions that are used:
Lock- All circuits are open ( no current supplied) and the steering wheel is in the lock position. In some cars, the transmission lever cannot be moved in this position. If the steering wheel is applying pressure to the locking mechanism, the key might be hard to turn. If you do experience this type of condition, try moving the steering wheel to remove the pressure as you turn the key.
Off- All circuits are open, but the steering wheel can be turned and the key cannot be extracted.
Run- All circuits, except the starter circuit, are closed (current is allowed to pass through). Current is supplied to all but the starter circuit.
Start- Power is supplied to the ignition circuit and the starter motor only. That is why the radio stops playing in the start position. This position of the ignition switch is spring loaded so that the starter is not engaged while the engine is running. This position is used momentarily, just to activate the starter.
Accessory- Power is supplied to all but the ignition and starter circuit. This allows you to play the radio, work the power windows, etc. while the engine is not running.
Most ignition switches are mounted on the steering column. Some switches are actually two separate parts;
The lock into which you insert the key. This component also contains the mechanism to lock the steering wheel and shifter.
The switch which contains the actual electrical circuits. It is usually mounted on top of the steering column just behind the dash and is connected to the lock by a linkage or rod.

NEUTRAL SAFETY SWITCH

Neutral Safety Switch

This switch opens (denies current to) the starter circuit when the transmission is in any gear but Neutral or Park on automatic transmissions. This switch is normally connected to the transmission linkage or directly on the transmission. Most cars utilize this same switch to apply current to the back up lights when the transmission is put in reverse. Standard transmission cars will connect this switch to the clutch pedal so that the starter will not engage unless the clutch pedal is depressed. If you find that you have to move the shifter away from park or neutral to get the car to start, it usually means that this switch needs adjustment. If your car has an automatic parking brake release, the neutral safety switch will control that function also.

STARTER RELAY

Familiarize Starter Relay

1.  Remove and Disconnect Starter Relay
2. Apply battery voltage to C and D terminals of relay
3. Check continuity between A and B terminals of the relay. it should exist.
4. Disconnect batterry voltage, there should be no continuity between A and B terminals of the relay
5. If relay does not operate as specified, replace relay

A relay is a device that allows a small amount of electrical current to control a large amount of current. An automobile starter uses a large amount of current (250+ amps) to start an engine. If we were to allow that much current to go through the ignition switch, we would not only need a very large switch, but all the wires would have to be the size of battery cables (not very practical). A starter relay is installed in series between the battery and the starter. Some cars use a starter solenoid to accomplish the same purpose of allowing a small amount of current from the ignition switch to control a high current flow from the battery to the starter. The starter solenoid in some cases also mechanically engages the starter gear with the engine.

THE MOST COMMON PROBLEM OF STARTING SYSTEM

Before discussing the preventive maintenance and diagnostic procedures for the starting system, were going to cover certain environmental and product application factors that can cause the starting system to malfunction.

Battery charge
 A battery having a low / poor state of charge will place abnormal stresses on the starting system. When measuring battery voltage, make sure voltage is 12.4 V or greater.

Excessive heat
A starter motor can become damaged if it operates too long at high temperatures. Excessive heat is generally due to continuous engagement of the starter. Damage to starting system components can occur when the starter motor is cranked for long periods (often due to cold weather starts, improperly tuned engine, etc.). Starter should operate for 30 seconds maximum then let to cool down for 2 minutes.
 
Excessive vibration
If starting system components are poorly or loosely mounted to the vehicle�s engine, the resulting vibration can damage sensitive internal components.
 
Corrosion, dirt, and dust
Starting system components operate less efficiently when corrosion forms or dirt particles build up around wire and cable connection points. Corroded and dirty connection points impair the flow of electrical current.
Improper use of starting fluid. Overuse and / or extended use of starting fluid places abnormal stresses on starting system components.
 
Defective solenoid
If the starter fails to engage or fails to stay engaged, the pull-in or hold-in coil may be defective, or the wiring to the solenoid is bad. You need to check the wiring to the solenoid. If the wiring is ok then the coil is defective and you will have to replace the solenoid.

JUMP START CABLE
Battery cables are large diameter, multi stranded wire which carry the high current (250+ amps) necessary to operate the starter motor. Some have a smaller wire soldered to the terminal which is used to either operate a smaller device or to provide an additional ground. When the smaller cable burns, this indicates a high resistance in the heavy cable. Care must be taken to keep the battery cable ends (terminals) clean and tight. Battery cables can be replaced with ones that are slightly larger but never smaller.

Spark Plugs

 SPARK PLUGS
The spark plug is in the center of the four valves in each cylinder.
­The spark plug is quite simple in theory: It forces electricity to arc across a gap, just like a bolt of lightning. The electricity must be at a very high voltage in order to travel across the gap and create a good spark. Voltage at the spark plug can be anywhere from 40,000 to 100,000 volts. The spark plug must have an insulated passageway for this high voltage to travel down to the electrode, where it can jump the gap and, from there, be conducted into the engine block and grounded. The plug also has to withstand the extreme heat and pressure inside the cylinder, and must be designed so that deposits from fuel additives do not build up on the plug.

Denso Sparkplug

IGNITION PERFORMANCE

The high voltage generated in the secondary winding of the ignition coil is discharged between the center and ground electrodes of the spark plug.
The sparking performance depends on many factors. The main factors affecting sparking performance are as explained below.

Spark plugs use a ceramic insert to isolate the high voltage at the electrode, ensuring that the spark happens at the tip of the electrode and not anywhere else on the plug; this insert does double-duty by helping to burn off deposits. Ceramic is a fairly poor heat conductor, so the material gets quite hot during operation. This heat helps to burn off deposits from the electrode. Some cars require a hot plug. This type of plug is designed with a ceramic insert that has a smaller contact area with the metal part of the plug. This reduces the heat transfer from the ceramic, making it run hotter and thus burn away more deposits. Cold plugs are designed with more contact area, so they run cooler.

Hot and Cold Plugs

Cold Plugs - is for hot engine
Hot Plugs - is for cold engine
The difference between a "hot" and a "cold" spark plug is in the shape of the ceramic tip.
The carmaker will select the right temperature plug for each car. Some cars with high-performance engines naturally generate more heat, so they need colder plugs. If the spark plug gets too hot, it could ignite the fuel before the spark fires; so it is important to stick with the right type of plug for your car.
Next, we'll learn about the coil that generates the high voltages required to create a spark.