Charging and Starting Systems Unit 8 Charging and Starting Systems

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Charging andStarting Systems

Unit 8

Charging and Starting SystemsObjective

Whether it’s a race car or an SUV, a crane or an excavator, electricity plays a key role in how machines operate. Yet, in almost all vehicles, there is a similar, basic electrical system to store electricity, draw on that stored electricity, and generate new electricity.When you have successfully completed this unit, you will understand how lead-acid batteries operate and how the charging and starting systems work in almost all combustion engine vehicles.

Overview

There is a similar basic electrical system in almost all vehicles that run by combustion engines. That basic electrical system involves a source for storing and dispensing electrical power, a method of generating new electrical power, and a way to use the stored electrical power to start the combustion engine. In this unit, you will learn how a battery stores and dispenses electrical power. You will learn about the alternator, which generates electricity and works with the voltage regulator to charge the battery and supply electrical power to the rest of the vehicle’s electrical system.

Figure 8.1 Basic components of a vehicle’s electrical system

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You will also learn about the starting system and the variations of components in the two circuits of the starting system. And fi nally, you will be introduced to remote start and stop functions associated with many mobile vehicles.

Battery Systems

Battery Basics

In mobile equipment, the battery system provides the electrical power to start engines, turn on lights, run electrical accessories and control devices. A battery stores electrical energy in the form of chemical energy (Figure 8.2). Storing energy in a battery is called charging the battery. Drawing energy out of a battery is called discharging the battery. When a battery is being charged, electrical energy is turned into chemical energy. When a battery is being discharged, chemical energy is turned into electrical energy.

Figure 8.2 Chemical energy processes occurring in a battery

Most mobile equipment uses lead-acid batteries. Some equipment uses more than one lead-acid battery and connects them in series or series-parallel arrangements. Most lead-acid batteries are twelve-volt batteries. Inside the polypropylene housing of a twelve-volt battery are six cells, each responsible for producing just over two volts of electrical energy. The cells are physically separated by partitions but connected electrically in series by metal connectors. Each cell is made up of lead plates separated by an electrolyte solution. Some of the plates are called the anode plates and have a positive charge. The other plates are called the cathode plates and have a negative charge. Each plate is made of lead, hardened with antimony or calcium. The plates are coated with chemically-active material. The positive plate is coated, or pasted, with lead peroxide, sometimes also called lead dioxide. Each molecule of lead peroxide has

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one lead atom and two oxygen atoms. The negative plate is coated with a porous type of lead called sponge lead. It has only lead atoms. Separators keep the plates apart to prevent short circuiting. An electrolyte is a fl uid that conducts electricity. An electrolyte has ions of electrons that can be rearranged when electricity passes through the fl uid. The electrolyte in a lead-acid battery is sulfuric acid diluted with water. In a lead-acid battery, it is this electrolyte that enables the chemical reaction. When a load is placed on a battery, a chemical reaction occurs. The electrolyte releases its sulfate molecules to both of the lead plates, and reacts with the positive plate to take the oxygen molecules. This reaction works to coat the lead plates with lead sulfate and change the electrolyte to H2O, or water as shown in Figure 8.3.

Figure 8.3 The chemical reactions that occur in a battery cell

When the battery is charged, the water molecules are broken into hydrogen and oxygen. The sulfate molecules from the lead plates return to the electrolyte, and the oxygen molecules from the water return to the positive plate. Gas is produced inside a battery when the hydrogen and oxygen molecules are separated during the charging cycle. Modern batteries have expansion and condensation chambers

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to prevent the gas from escaping. However, care should still be taken to avoid any sparks when working around a lead-acid battery. In practical use, it is unlikely to fully charge or discharge a battery. Typically, a battery is partially charged and partially discharged. For example, if a battery is ten percent discharged, that means that ten percent of the chemical reaction has taken place, and ninety percent of the battery is in the normal, charged state. A battery may test at twelve-point-six volts, indicating that it is fully charged, but that does not necessarily mean that the chemical state inside the cells is entirely charged.

Charging System

Charging System Basics

The charging system (Figure 8.4) includes the battery, or in some cases multiple batteries, an alternator, a voltage regulator, the loads of the vehicle, and the wiring between all of these parts. The charging circuit has two main jobs: fi rst, to recharge the battery, and second, to provide most of the current needed to power all of the electrical components of the vehicle, once the engine is running.

Figure 8.4 The components of a simple charging system

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The battery is like a reservoir of energy. It stores energy in the form of chemical energy. When a load is placed on this chemical energy, it quickly starts turning into electrical energy and electrons fl ow through the circuit. The alternator is the workhorse of the charging system. It is usually connected to the crankshaft of the engine by a belt. Once the engine is running, the rotation of the engine’s crankshaft becomes mechanical energy in the rotation of the belt. The belt transfers this mechanical energy to turn the rotor inside the alternator. The alternator changes this mechanical energy into electrical energy. Then the alternator acts like an electron pump, pushing electrons through the circuit to supply current for the lights, radio, heater, ignition, and other components in the electrical system. The alternator also pumps electrons back into the battery to keep it charged.The electrical charge in a battery, called voltage, acts like pressure. A heavy-duty twelve-volt battery (Figure 8.5) is considered fully charged when it has twelve-point-six volts of electrical pressure available. As the battery sends out current and discharges, the voltage or electrical pressure drops. The more discharged the battery, the lower the voltage or electrical pressure, and the easier it is for the alternator to pump in electrons against the remaining pressure. The higher the voltage or electrical pressure in a battery, the harder the alternator has to work against that pressure to charge the battery. In a twelve-volt system, the alternator generally sends 14.2 volts of electricity to the battery. In a twenty-four-volt system, the alternator generally sends between 27.5 and 29.5 volts to the battery.

Figure 8.5 The voltage regulator detects when there is a load on the system

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The voltage regulator is the traffi c cop of the charging system. It directs the amount of electrical traffi c from the alternator to the battery and to the rest of the vehicle’s electrical system. The regulator senses when the vehicle’s electrical needs increase or when the battery needs charging. The regulator then adjusts the alternator’s electrical output to the system or the battery.An alternator can make hundreds of instantaneous adjustments each minute. The battery, alternator, and regulator work together to keep the vehicle’s electrical system supplied. When the engine is not running, and at start-up, the battery supplies all of the current for the loads. When the engine is running and the vehicle is operating with normal loads, the alternator supplies current to the system and charges the battery as needed. When the engine is running and the vehicle is operating with low loads, the regulator may direct more current fl ow from the battery and allow the alternator to freewheel for fuel economy, since a one-hundred-amp alternator can consume up to seven horsepower. When the vehicle is operating with peak electrical loads, the regulator directs the alternator and the battery to work together as a team to supply all of the needed current.

Starting System

Starting System Basics

One of the most important systems in a vehicle is the starting system. Its work is occasional and short, but critical. When the starting system isn’t working, the vehicle won’t work.The starting system works by taking electrical power stored in the battery, sending that power to a starter motor, where the electrical power is converted to mechanical power, and using that mechanical power as rotation to crank the engine and get the engine up to speed to operate on its own. When the engine is operating, the work of the starting system is completed and other systems take over the operation of the vehicle.The basic components in the starting system (Figure 8.6) include: the battery, which supplies the energy, heavy-gauge electrical cables, which transfer the energy to the starter motor, the starter solenoid, which engages the starter motor drive with the engine fl ywheel, the starter motor, which drives the fl ywheel to crank the engine, and the starting, or ignition switch, which activates the starting circuit.

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Figure 8.6 The basic components of a starting system

The fi rst component to activate is the starting switch. This could be a key switch or a start button. When the starting switch is activated, a circuit is closed and electricity fl ows from the battery, through the cables, to the starter solenoid. When the starter solenoid receives electricity in its coils, a magnetic fi eld is created, and this magnetic fi eld moves the solenoid plunger. The movement of the solenoid plunger accomplishes two things: it engages the starter pinion with the fl ywheel of the engine, and it completes the circuit between the battery and the starter motor.The starter motor is an electric motor designed to deliver high power for a short time. When the motor is energized, it creates torque to drive the rotation of the starter pinion, and the starter pinion turns the fl ywheel, which cranks the engine into operation. When the starter button is released, or the ignition switch key is released from the start to the run position, the solenoid is deactivated. Springs force the solenoid plunger to return, and this draws the pinion away from the engine’s fl ywheel and opens the starter motor circuit, which stops the starter motor.

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Control and Crank Circuits

There can be many other types of components included in a starting system. The components are arranged in two interconnected circuits: the cranking circuit and the control circuit.A large starting motor can draw more than three-hundred amps of current from the battery. That is why heavy-gauge cables connect the battery directly to the starter motor. This is the basic cranking circuit, from the battery to the starter motor.The control circuit is set up as a separate circuit, but interconnected with the cranking circuit. This allows a small amount of battery current in the control circuit to control a larger amount of current in the cranking circuit. Since the control circuit is not directly part of the cranking circuit, there is less resistance to be overcome than in the very large power needs of the cranking circuit.

Figure 8.7 Cranking circuit showing largecurrent from the battery to the starter

Starting Components

Different manufacturers use different confi gurations of components. In this course, we are covering the basic system, and only touch on some of the variations.

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When working on a system, make sure to refer to the specifi c shop manual for that equipment. Typical components (Figure 8.8) may include: a neutral safety switch, a starter relay, also called a magnetic switch, a safety relay, a battery relay, a master switch, a fusible link, and a thermostat.A neutral safety switch is a safety device. If you try to start the engine when the vehicle is in gear, the vehicle could suddenly lurch forward or backward. If the vehicle is in gear when you turn the key, the neutral safety switch is open and no electricity fl ows through the control circuit. When the vehicle is in park or neutral, the neutral safety switch is closed and electricity can fl ow through the control circuit. Generally, the neutral safety switch is located on the gearshift lever or transmission linkage.

Figure 8.8 Various starting system components

The starter relay is also called the magnetic switch. It enables a small current in the control circuit to open and close the larger current in the cranking circuit. The starter relay is either built into the front end of the starter’s solenoid assembly, or it is remote mounted either close to the battery or close to the starter.A safety relay prevents current from going to the starter motor after the engine is running. This prevents damage to the pinion and fl ywheel by preventing them from making contact when the fl ywheel is activated. There are two main types of safety relays (Figure 8.9): the older mechanical type, which uses coils and contact

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points, and the newer semi-conductor type. Safety relays can be mounted in various places, so check the shop manual for the exact type and location.

Figure 8.9 A mechanical safety relay and a semi-conductor safety relay

A battery relay removes electricity from wires that are not in use. This prevents possible short circuits. It also prevents electrical shock when you are making repairs or replacing components. A battery relay can be located on either the positive or negative side of the battery.A master switch is another type of device to remove electricity from wires that are not in use. It is a manually operated battery disconnect switch. The master switch is located between the battery and the chassis ground.A fusible link is an over-current protection device for the system. The most common type of fusible link is a section of wire covered with nonfl ammable insulation. Generally the wire is two sizes smaller than the wiring of the circuit it is designed to protect. When a system is heated with overcurrent, the fusible link breaks and opens the circuit. Usually, the insulation will appear charred. However, you should do a continuity test on it to make sure. Typically, the largest fusible link is located at the starter solenoid battery terminal. There is often another fusible link between the battery terminal and the main body harness. This link protects the complete wiring of the vehicle.

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Some starter motors have a thermostat to monitor the temperature of the starter motor. If the starter motor is run too long, the temperature builds and the thermostat breaks the circuit. When the thermostat senses that the motor has cooled suffi ciently, it will again close the circuit.

Remote Start & Stop

On some vehicles, such as bucket trucks, some fi re trucks, digger derricks, and other utility vehicles, there is a need to interact with the starting system from outside of the cab. A remote start/stop unit allows operators to start and stop the engine without re-entering the cab. A remote control system can be as simple as only starting and stopping the vehicle or as complicated as operating all of the functions of the vehicle. The remote control unit can be mounted on the vehicle, with signals sent to the vehicle’s electrical system through electrical cables or fi ber optic cables. The remote control station can also be a mobile transmitter that sends radio wave signals to a receiver connected to the vehicle’s starter system and other electrical systems. Always refer to the remote control manual when working with a vehicle equipped with a remote control device.

Figure 8.10 Examples of remote start and stop controls

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SUMMARY

The battery system provides the electrical power to start engines, turn on lights, run electrical accessories and control devices.A battery stores electrical energy in the form of chemical energy.The charging system includes the battery, an alternator, a voltage regulator, the loads of the vehicle, and the wiring between all of these parts.The starting system works by taking electrical power stored in the battery, sending that power to a starter motor, where the electrical power is converted to mechanical power, and using that mechanical power to crank the engine.There can be many types of components included in a starting system. The components are arranged in two interconnected circuits: the cranking circuit and the control circuit.Typical starting components include: a neutral safety switch, a starter relay, also called a magnetic switch, a safety relay, a battery relay, a master switch, a fusible link, or a thermostat.

QUESTIONS

Battery Basics1. Batteries store energy in which form? a. electrical energy b. chemical energy c. mechanical energy d. light energy

2. How much potential does each cell within a 12 volt battery produce?

a. just under three volts b. just over two volts c. just under two volts d. It depends on the number of

cells present.

3. What material is used to coat the positive, or anode, plate of a battery?

a. lead peroxide b. sponge lead c. sulfuric acid d. aluminum

4. In a lead-acid battery, it is the electrolyte that enables the chemical reaction.

a. True b. False

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Charging System5. Which is NOT typically part of a

charging system? a. battery b. voltage regulator c. capacitor d. alternator

6. Which part controls the amount of electricity fl owing into the vehicle’s electrical system?

a. solenoid b. crankshaft c. regulator d. alternator

7. The only job of the charging system is to charge the battery.

a. True b. False

8. The alternator converts ________ energy into ________ energy.

a. mechanical, electrical b. chemical, mechanical c. electrical, mechanical d. electrical, chemical

9. In a twelve-volt system, how many volts does an alternator generally send to the battery?

a. 12 V b. 12.6 V c. 13 V d. 14.2 V

Starting System & Remote Start and Stop10. Which is NOT a basic component of

the starting system? a. alternator b. heavy-gauge electrical cables c. starter solenoid d. ignition switch

11. What is the purpose of the neutral safety switch?

a. It prevents current from going to the starter motor after the engine is running.

b. It removes electricity from wires that are not in use.

c. It prevents the engine from starting if the vehicle is in other than neutral or park.

d. It allows a circuit to be grounded to the frame.

12. What is the purpose of a safety relay? a. It prevents current from going

to the starter motor after the engine is running.




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13. What is the purpose of a battery relay? a. It prevents current from going

to the starter motor after the engine is running.




14. Generally, how would you compare the size of a fusible link wire to the size of the wiring of the circuit it is designed to protect?

a. It is the same size. b. It is two sizes bigger. c. It is two sizes smaller. d. It is three sizes bigger.

15. What is a benefi t of a remote start/stop system?

a. It breaks the starter motor circuit if the temperature is too high.

b. It prevents electrical shock when you are making repairs or replacing components.

c. It saves wear and tear on the brake system.

d. It allows you to start and stop the engine without re-entering the cab.

Charging and Starting Systems Unit 8 Charging and Starting Systems

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