8 basic electrical (2cr.)
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Auto. Basic Electrical Auto. Basic Electrical Milwaukee Area Technical CollegeMilwaukee Area Technical College
10-602-101 Automotive Basic Electrical (2cr.)
Presenter: David Schwid
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Lesson 2: Atoms•Smallest part of an element •Still has all the characteristics of that element•Can be solid, liquid, or gas.
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Atoms•Atoms consist of three parts:
A. Protons (positively charged)
B. Neutrons (neutral
charged)C. Electrons (negatively charged)
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AtomsPositive and negative charges act
like those in a magnet
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Electron flowAll electrons do not travel in the same orbit. All electrons do not travel in the same orbit. Some are closer to the nucleus and some are Some are closer to the nucleus and some are farther away. The electrons in the outer orbits farther away. The electrons in the outer orbits are sometimes called “free” electrons.are sometimes called “free” electrons.
The outer ring is called a valance ring and the The outer ring is called a valance ring and the electrons in the outer orbits may also be electrons in the outer orbits may also be called valance electrons.called valance electrons.
Elements with 1-3 valance electrons are Elements with 1-3 valance electrons are usually good usually good conductors.conductors.
Elements with 4 valance electrons are Elements with 4 valance electrons are semi-semi-conductors.conductors.
Elements with 5 or more valance electrons Elements with 5 or more valance electrons are usually good are usually good insulators.insulators.
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ElectricityDefinition- Flow of Electrons
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Conductors• Allow the flow of electricity• Contain atoms with free electrons
– 1 to 3 electrons in the outer orbit• Free electrons are not locked in orbit
around the nucleus– electrons can be forced to move from one
atom to another• Copper, gold, and silver are good
conductors
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Semi-Conductor• Allow small amount of electricity to flow
– 4 electrons in outer orbit• Human body is a semi conductor
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Insulators• Resist the flow of electricity• Contain atoms with bound electrons
– 5 to 8 electrons in the outer orbit• Bound electrons will not leave their orbit
around the nucleus• Plastic, rubber, and ceramics are good
insulators
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Section 2: Lesson 1
Conductors/InsulatorsConductors are materials Conductors are materials
that allow current to flow that allow current to flow easily. easily.
Insulators are materials Insulators are materials that are very resistant to that are very resistant to current flow. Insulators current flow. Insulators are used to prevent an are used to prevent an unwanted current path.unwanted current path.
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AC/DC
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Direct Current• Direct Current only flows in one
direction.• For the purposes of this course, we will
say it only flows from positive to negative. Conventional (current) theory
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Alternating Current• Alternating Current flows back and forth from
positive to negative and from negative to positive.
• A/C is produced by a magnetic field passing through a conductor.
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Lesson 3:Electromotive Force
VoltageVoltage is the “Electrical Pressure” Voltage is what pushes the electrons through the conductor. It can also be referred to as Potential Difference.
Hint: (think water pressure)
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Amps• Current
– Number of electrons that flow past a point in one second
– Measured in Amperage
• Hint- (think Gallons per Minute)
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Amperage is how we measure electron flow or current. One ampere or amp is 6.25 billion billion electrons past one point in one second!
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Characteristics of Current• When current flows
through a conductor, it generates heat and magnetism. Energy is only transformed, it is never lost.
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Resistance• Resistance is the opposition to flow of
electrons in a conductor. • Measured in ohms (Ω)• Hint- (think water facet)
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Resistance• There are several factors that affect the
resistance of a conductor. They are:– Diameter
– Length
– Material
– Temperature
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WiresSome examples of different wires.– Solid Copper is
almost never used.– Hi-Flex 266 used in
ABS.– Multi-Stranded is
the most common.– Twisted & Shielded
used in signal and communications.
– Ribbon Wire for space savings.
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Wire Size
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Wire Stripping & Crimping
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Soldering
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Connectors and Terminal Repair
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Lesson 5: Laws
Ohm’s Law
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Ohm’s Law
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Ohm’s Law
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Ohm’s Law
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Voltage Unknown
E= I x R
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Resistance Unknown
R= E / I
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Current Unknown
I= E / R
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Simple Circuit• Three things
– Power supply– Conductor– Load
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Series CircuitCurrent is the same throughout the
circuit.
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Series Circuit Rules
If voltage remains constant and resistance increases, amperage flow will decrease.
If voltage remains constant and resistance decreases, amperage flow will increase.
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Parallel CircuitsThe total resistance of a parallel circuit will always be less than the resistance of any of it’s branches.
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Parallel Circuit RulesThe total resistance of a parallel circuit will always be less than the resistance of any of it’s branches.The voltage applied to each branch is the same.The current flow through the branches will be different if the resistance is different.The voltage dropped across each branch will be the same.
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Parallel Circuits– The voltage applied to each branch is
the same.
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Parallel CircuitsThe current flow through the branches will be different if the resistance is different.
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Parallel Branch Amperage As more branches are added, more
amperage flows.
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Series-Parallel CircuitCalculate the total resistance of the parallel circuit first, using the appropriate formula.Add that to the total resistance of the series portion of the circuit.This will give us the total resistance of the circuit.
– Now we can calculate the total circuit current flow, because we know what the source voltage is.
I = E / R
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Circuit Faults• Open- Break in Circuit• Short- Two positive wires touching• Short to Ground- positive wire touching
ground• High resistance- Bad connection
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Open•No completed path to ground
– Series circuit– Parallel Circuit
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Short to Ground•Before the load
– Protection device opens– Why?– Resistance decreased– Current increased
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Short to Ground•After the load
– Load stays on if ground side switched
– If close to intended ground, no noticeable effect
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Short to Power•One or more circuits may operate strangely
– Figure 8-3, view A, both switches control both loads– Figure 8-3, view B, short to ground
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Too Much Resistance•Dirt or Corrosion
– As resistance increases– Current flow decreases– Voltage needed to operate load drops
in another part of the circuit
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Reading the Meter• Types
– Digital• Manual Ranging• Auto Ranging
– Analog• Analog has low
internal impedance/allowing more current to flow
• Do Not Use on any computer controlled circuits
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Units of MeasureM = MEGA or 1,000,000
K = KILO or 1,000m = MILLI or 1/1000th
2.5 M ohms = 2,500,000 ohms.250 M ohms = 250,000 ohms
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Mega Mega stands for one million and is abbreviated with a capitalletter M. One mega ohm equals one million ohms. To convertany value from mega ohms to ohms, move the decimal point sixplaces to the right. For example, 3.5 mega ohms will convert to3,500,000 ohms.
Kilo Kilo means one thousand and is abbreviated with a lowercase letter k. A kilo ohm is equal to 1,000 ohms. To convert any value from kilo ohm to ohms, move the decimal point three places to the right.
For example, .657 kilo ohms will covert to 657 ohms.
Base Units
Base units are standard units without a prefix. Volts, ohms, and amperes are the primary base units used in electronics. Prefixes are added to base units to change the unit of measurement.
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Milli Milli stands for one thousandth and is abbreviated by the lowercase letter m. A milli ampere is one-thousandth of one ampere. To convert any value from milli amperes to amperes, move the decimal point three places to the left. For example, 0.355 milli amps will convert to .000355 amps.
MicroMicro means one millionth and is abbreviated by the symbol u. A microampere is equal to one millionth of an amp. To convert any value from microamperes to amperes, move the decimal point six places to the left. For example, 355 microamperes will covert to .000355 amps.
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Reading the Meter
You must know what to expect before taking the reading…….or you’re wasting your time!
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Lesson 2:Circuit Protection
Devices designed to open the Devices designed to open the circuit in the event of too much circuit in the event of too much current flow.current flow.
FuseFuse
Fusible LinkFusible Link
Circuit BreakerCircuit Breaker
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Switches
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RelaysA relay is an electric switch that uses a small current to control a larger current. A relay consists of an electromagnet, an armature, and a set of contacts. Some may also contain a clamping diode or resistor. An example of a relay is an A/C clutch relay
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RelaysA control circuit (primary circuit) is used to provide current to the electromagnet. The electromagnet is energized and pulls the armature toward it. The movement of the armature closes the normally open contacts (secondary circuit). When the contacts close they provide a path for current to reach the load.
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RelaysWhen the electromagnet is de-energized, current reverses and produces a voltage spike. This spike results from the collapsing of the magnetic field around the coil. Voltage spikes can damage electronic components. To prevent this spike, a clamping diode or resistor is wired in parallel with the relay coil, providing a path for this current to return back to the coil without causing harm to the electronic components.
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Section 3: Lesson 1
Electrical Measurement DVOM Setup
Click on the Following Link for an animated learning object about:Wisc-Online: Digital Multimeter/Ohmmeter Measurement Connections
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Reads the voltage difference between the lead ends
Amperage must be flowing to measure Voltage Drop
Red Lead: Voltage/Ohm PORTBlack Lead: COM PORT
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Amperage Testing
A/C or D/C Amperage
Options:Milli-Amps/AmpsMicro-Amps
Red Lead: Amp Port (10 amp max)or milli-amp / micro amp portBlack Lead: COM Port
Always hooked in SeriesAmperage must be flowing to measure
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Place around 1 wire -Not required to place inseries
Amperage must be flowing to measure
Dial set to D/C mV scale
Red Lead: Voltage PortBlack Lead: COM Port
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The lower the reading the better the path quality
OL means “OVER LIMIT” of the meterto read (check the scale the meter is set at)OL means “NO Path of electricity”
**The wire or component must be isolated from the power and groundSource**Red Lead: Ohm PortBlack Lead: COM Port
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Diode Testing
Performs a continuity test with a higheroutput voltage to “Turn On” the diode.
The meter will read the voltage output
Red Lead: Volt/Ohms/Continuity PortBlack Lead: COM Port
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Lesson 1: Symbol Identification
Common Symbols
Symbols are used to represent various electrical components. These are referred to as schematic symbols and are used extensively in automotive publications for diagnosing electrical concerns.
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Ground Symbol
Because automotive circuits share a common ground, that is, a return path to the battery, a special ground symbol is used to simplify circuit diagrams.
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Circuit Protection
Circuit breakers and fuses are two types of circuit protection devices.
They are designed to create an open If the specified amount of amps are exceeded.
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Resistors
Resistors are used to limit current, divide voltage, and in certain applications, generate heat. There are a variety of resistors classified into two main categories: fixed and variable.
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Wire and Wire Symbols
Wire is the most common type of conductive material used to connect components.
Wire is available in different sizes called gauge size.It is also available in both round and flat types.
This is the symbol for wires that cross, but are not connected.
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Splice
This is the symbol for wires that cross and are connected at a splice.
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Continuation / Optional
A wavy line means a wire is to be continued somewhere else in the circuit. Typically, these lines are used to show a graphically shortened wire.
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Continuation
An arrow symbol at the end of a wire with a letter inside of it indicates a wire continues as labeled on another page. For example, this wire connects to the generator, but it is shown on another page. The symbol is then repeated on that page. The arrow indicates the direction of current flow.
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SwitchSwitches are most commonly used to control a circuit by either allowing or restricting voltage flow. Switches can be mechanical, or electromechanical, or electronic. Switches can be in a multiple of different configurations, such as SPST (single pole, single throw).
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Battery
A battery provides a source voltage for an electrical/electronic circuit. Most batteries work by the conversion of a chemical reaction into electricity.
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Motor
A motor provides the conversion of electrical potential into amoving mechanical energy.
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Light Bulb
A light bulb converts electrical energy into a radiant light. The filament resists electrical flow and heats up, causing the filament to glow.
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Blower Motor Circuits• Power flow in
High Speed– Feed Power– Switched
Power– Switched
Ground– Hard Ground
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Blower Motor Circuits• Power flow in
Medium High (M2) Speed – Feed Power– Switched
Power– Switched
Ground– Hard Ground
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Power Window Circuits• Power flow
with switches off.– Feed Power– Switched
Power– Switched
Ground– Hard
Ground
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Power Window Circuits• Power flow
with L.F. up.– Feed Power– Switched
Power– Switched
Ground– Hard
Ground
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Power Window Circuits• Power flow
with L.F. down.– Feed Power– Switched
Power– Switched
Ground– Hard
Ground
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Power Window Circuits• Power flow
with R.F. control down.– Feed Power– Switched
Power– Switched
Ground– Hard
Ground
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• What voltages should you read at the given points?
• Where should you place the leads?
Power Window Circuit Diag.
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Wiper Motor Circuit• Power flow
with the wipers in low.– Feed Power– Switched
Power– Switched
Ground– Hard Ground
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Wiper Motor Circuit• Power flow
with the wipers in high.– Feed Power– Switched
Power– Switched
Ground– Hard Ground
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Wiper Motor Circuit• Power flow
with the wipers going to park.– Feed Power– Switched
Power– Switched
Ground– Hard Ground
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Wiper Motor Circuit• Power flow
with the wipers parked.– Feed Power– Switched
Power– Switched
Ground– Hard Ground
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Wiper Motor Circuit Diag.• What
voltages should you read at the given points?
• Where should you place the leads?
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• An automotive battery is an electrochemical device
• It produces and stores direct current electricity
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Batteries
The battery provides the electricity to power all systems of the vehicle
when the engine is not running. When the engine is running, the charging system supplies all the
electricity to power the systems of the vehicle and the battery helps to
stabilize voltage for the entire electrical system.
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Battery Parts
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Discharging• Changes chemical energy into electrical
energy• Stored energy is released
ChargingElectrical energy is converted to
chemical energyEnergy is stored until needed
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Lead-Acid Battery Cell
Electrolyte causes a chemical reaction between the plates, producing 2.1 volts
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Battery Element
Most automotive batteries havesix elements
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Battery Voltage• Open circuit cell voltage is 2.1 volts• Cells are connected in series• Battery voltage depends on the number
of cells• 12 volt battery has 6 cells - open circuit
voltage 12.6 volts• 6 volt battery has 3 cells - open circuit
voltage 6.3 volts
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Batteries BATTERY STATE OF CHARGE
Once fully charged, a 12 volt battery will produce 2.1 volts per cell. For example, a 12 volt battery =
2.1 volts x 6 cells = 12.6 volts.
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Battery Voltage
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Cell Action(Charging)
• Alternator causes free electrons to be deposited on the negative (–) plate
• This causes the plates to have a difference in potential (voltage)
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Cell Action(Discharging)
• Load is connected across the terminals• Current flows through the load to
equalize the difference in charges on the plates
• Excess electrons (current) move from the negative plate through the load to the positive plate
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Battery Cycling
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Electrolyte• Mixture of sulfuric acid and distilled
water• Poured into each cell until plates are
covered• Warning: causes serious burns or
blindness, if it comes in contact with your skin or eyes!
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Batteries BATTERY STATE OF CHARGE:
With a maintenance possible battery, the technician can check the charge in each cell with a
hydrometer. A hydrometer measures the specific gravity of the electrolyte. If the battery is fully
charged it will have a specific gravity of 1.265. The lower the specific gravity the weaker the charge.
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Hydrometer Check• Measures specific gravity (SG)• Compares weight of electrolyte to water• Water has a SG of 1.0• Electrolyte in a fully charged battery is
more dense with a SG of 1.265 to 1.299• As a battery becomes discharged,
electrolyte has a higher percentage of water, and a lower SG
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• Does not use removable filler caps• Calcium is used to make the plates,
reducing gassing• Reduced water loss decreases service
requirements
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Batteries BATTERY STATE OF CHARGE
Auto. Basic Electrical Auto. Basic Electrical Milwaukee Area Technical CollegeMilwaukee Area Technical CollegeCharge Indicator
Changes color to show the general state of charge of
the battery
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Battery Terminals
Means of connecting the battery to the
vehicle’s electrical system
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Two-Battery Systems• Parallel
– connected negative to negative– connected positive to positive– two 12 volt batteries produce 12 volts, high
current• Series
– connected positive to negative– two 12 volt batteries produce 24 volts
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Battery Cables
A. Post-typeB. Side terminalC. Braided groundD. 90º post-typeE. Solenoid to
starter
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Cable Connections
Negative grounds engine block and positive connects
to electrical system
Auto. Basic Electrical Auto. Basic Electrical Milwaukee Area Technical CollegeMilwaukee Area Technical CollegeWet- and Dry-Charged Batteries
• Wet-Charged Battery– Filled with electrolyte and charged at
the factory– Very common in many locations
• Dry-Charged Battery– Contains fully charged elements– Does not contain electrolyte– Leaves the factory in a dry state– Has a long shelf life
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Cold Cranking Rating• Determines the current that the battery
can deliver for 30 seconds at 0 ºF (-18 ºC) while maintaining terminal voltage of 7.2 volts (1.2 volts per cell)
• Expressed as cold cranking amps (CCA)• Indicates ability to crank the engine at cold
temperatures• Typical applications:
– 305 CCA for small 4 cylinder engine– 450 CCA for 8 cylinder engine
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Battery Sizes and Ratings• CCA (Cold Cranking Amps)
– # of Amps produced in 30 seconds
– 0 deg. F– Maintaining at least 7.2V.
Don’t confuse CCA with CA!
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Battery Sizes and Ratings• CA (Cranking Amps)
– # of Amps produced in 30 seconds
– 32 deg. F– Maintaining at least 7.2V.
Don’t confuse CCA with CA!
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Temperature Versus Efficiency
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Parasitic Loads• Current draw present when engine and
ignition are shut off• Computers and clock require constant
power• Over prolonged periods, these may
discharge the battery enough to prevent starting
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Battery Problems
Visually inspect batteries for these kinds of problems
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Battery Leakage Test• Tests for current discharge across the
top of the battery• Set a voltmeter to a low voltage range• Use acid-resistant probes• Touch negative lead to negative terminal• Using positive lead, probe top of battery• Clean battery if voltage is above 0 volts
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Battery Leakage Test
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Battery CleaningWash with baking soda and water, and do
not let debris enter filler openings
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Battery Terminal Test• Tests for poor battery cable connection
at battery• Connect negative voltmeter lead to
cable end• Connect positive lead to the battery
terminal• Disable injection or ignition and crank• Clean connections if voltage is above
0.5 volts
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Battery Terminal Test
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• Unplanned voltage drop– An unplanned voltage
drop can happen anywhere in a circuit.
– In this example “A” represents corrosion in a wire.
– The light bulb is dim because the corrosion has consumed too much of the available voltage.
Voltage Drop
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Voltage Drop• Unplanned voltage drop
– Many things can cause unplanned voltage drops. Loose connections, corrosion, burned contacts...just to name a few.
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Removing Battery Cables
Different methods of
removal
Auto. Basic Electrical Auto. Basic Electrical Milwaukee Area Technical CollegeMilwaukee Area Technical CollegeCleaning Battery Posts and Cable Ends
Rotate female end
of brush on post
Use male end ofbrush on cable
end
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Reconnecting Battery Cables
Before reconnecting, coat connection with
petroleum jelly or white grease
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Battery Drain Test• Tests for abnormal current draw with
ignition off• Remove battery cable and connect an
ammeter in series in the circuit• Disable all lights and clock circuit• Compare ammeter reading to
specifications• If reading is high, isolate problem by
pulling one fuse at a time
Auto. Basic Electrical Auto. Basic Electrical Milwaukee Area Technical CollegeMilwaukee Area Technical CollegeBattery Drain TestTypically maximum 10 milliamps (mA)
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Battery Chargers• Force current back into the battery to
restore the charge on the plates• Change 120 volts AC to 14–15 volts DC
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Slow Charger
• Often called a trickle charger• Feeds a small amount of current into
battery• Best for long term battery service• Typical slow charge is about 12 hours
at 10 amperes
Auto. Basic Electrical Auto. Basic Electrical Milwaukee Area Technical CollegeMilwaukee Area Technical CollegeFast Charger• Forces high current flow into battery• Allows engine start from a low battery in
a few minutes
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• Connecting a vehicle with a good battery to one with a low battery
• Connect positive terminals together with red jumper cable
• Connect black jumper cable to a good ground on each vehicle
• After starting, remove black cable first• Avoid arcing near the battery
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Jumper Cable ConnectionRun the engine in the vehicle with the live
battery while cranking the other one
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• Measures the current output under load• Determines actual battery performance• Used on batteries with open circuit
voltage of 12.4 volts or higher
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Load TesterThe most accurate
method of determining battery condition
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Determining Load
• Three times the amp-hour rating– 60 amp-hour battery– 60 x 3 = 180 amperes
• One half the cold crank rating– 400 CCA– 400 ÷ 2 = 200 amperes
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Loading the Battery
• Turn the load control knob until the ammeter reads the correct amperage
• Maintain load for 15 seconds• Read the voltmeter at 15 seconds• Minimum 9.5 volts at room temperature
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Load Test ResultsIf the reading is below the voltage in the
chart, the battery is probably bad
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Micro-Type Testers• The new standard for batter
y testing (Click for L.O.)• Required by many OEM for
warranty• Uses conductance (the
ability to conduct current) to measure battery condition
• The battery does not need to be fully charged to test.
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3 Minute Charge Test• Determines if the battery is sulphated• Performed if battery is in low state of
charge• Charge for 3 minutes at 30-40 amperes• Test voltage while charging• If the voltage goes above 15.5 volts,
battery should be replaced