Automotive Electrical Notes Automotive Electrical Notes PHS Auto 2PHS Auto 2
Basic notes for auto shop classBasic notes for auto shop class
study and refer back to your text bookstudy and refer back to your text book
Electron theory the electrical phenomenon is produced
by a flow of electrons from one area to another.
The flow of electrons is caused by having an excess number in one area, shortage in anothersurplus negativeshort supply positive
Flow of electronsFlow of electrons
Matter
Anything that takes up space and has mass: solid, liquid or gas
Molecule
Smallest portion of matter and retain all original properties of the original matter, it is made up of atoms
Atoms 100 + different types One molecule of water, is made up of one
atom of oxygen, two atoms of hydrogen H20
Atom make up
PROTON - positive charge + ELECTRON - negative charge - NEUTRON - no charge (neutral)
If there are more protons in the atom then electrons, it is a positive charged atom.proton and neutron in center; electrons orbit
Size of atom ?
Bound electrons
Are in the inner orbits, Bound electrons are very difficult to remove from their orbit.
Free electrons
Outer orbits only, one, two or three electrons, are easily knocked out of their orbit
Conductors Have 1-3 electrons in outer orbit, (Free
electrons)easily knocked out of orbit. Materials such as silver, copper, aluminum, gold make good conductors.
Semi-Conductors 4 electrons in outer orbit
Not a good conductor Not a good insulator
Non conductors Insulators, 5 or more electrons in outer
orbit, glass, ceramics, plastics, rubber, fiber, porcelain, paper and wood are common Insulators. Hard to knock the electrons out of orbit if they have a strong magnetic pull to the protons in the nucleus of the atom.
Current
Movement of free electrons through a conductor current flow is measured in amperes(Amps). Must have shortage of electrons at one end, surplus at other one electron does not go the whole distance moves and bumps others.
Voltage (electromotive force, EMF)
Pressure differential causes current to flow, this pressure is known as voltage
Voltage is a measure in volts with voltmeter.
Resistance Caused by electrons bumping into other
atoms, a poor conductor has greater resistance than a good conductor. Poor conductors will heat up (like a heater).
Larger conductors (wire size) offers less resistance then a smaller one,
Resistance is measured in ohms Current will flow in the one path with least
resistance. Current will flow from negative to positive,
negative has surplus of electrons, positive has short supply.
Which way does it flow ? Ask the experts
Circuits Must have a power source. A load (something to operate such as a
light bulb or motor) Wiring for path of electron flow
(Conductor) Switch Circuit protection
Thanks Kevin http://www.autoshop101.com/
Series circuit, only one path for current to flow
Series CircuitSeries Circuit
Parallel circuit, more than one path for current to flow, current flows through all units at once.
Parallel CircuitParallel Circuit
Series parallel, combination of both circuits.
Series ParallelSeries Parallel
Circuit ProblemsCircuit Problems Open circuit, Wire is broken Short to ground, Wire is touching ground Short to voltage, wire is touching a hot
wire. Load device is on even though switch is off.
High resistance, current is being slowed by corrosion or a poor connection
Car frame Acts as a ground wire, some cars like a
corvette have to run ground wires because of fiberglass body
Ground symbol:
Ohms law
Amperes = I - Intensity Volts = E - Electromotive force Ohms = R - Resistance
to find E = I x RI = E / RR = E / I
I X R
E
Ohms laws For Auto Techs
Some Auto Techs will use the following Amperes = A - Amps Volts = V - Volts Ohms = R - Resistance
to find V = A x RA = V / RR = V / A
A X R
V
M, m, K, M, m, K, μμ
PrefixPrefix SymbolSymbol FactorFactor NumericallyNumerically NameName
gigagiga GG 101099 1 000 000 0001 000 000 000 billionbillion
MegaMega MM 101066 1 000 0001 000 000 millionmillion
kilokilo kk 101033 1 0001 000 thousandthousand
centicenti cc 1010-2-2 0.010.01 hundredthhundredth
millimilli mm 1010-3-3 0.0010.001 thousandththousandth
micromicro μμ 1010-6-6 0.000 0010.000 001 millionthmillionth
nanonano nn 1010-9-9 0.000 000 0010.000 000 001 billionthbillionth
MagnetismMagnetism Materials that have this are called MagnetsMaterials that have this are called Magnets Some are NaturalSome are Natural Some are madeSome are made
Magnetic Domains These small sections of a magnet must
all line up to be a strong magnet.If not, they will cancel each other out and the piece of metal will be unmagnetized
Lines of Force Leave north pole, enter south Unlike poles attract Like poles repel Left hand rule, know which way current
flows, fingers point in direction magnetic field is moving
Magnetic fields surround any conductor carrying an electrical current
Lines of Force
magnetic effects of parallel conductors, magnetic effects of conductors with
current flowing in opposite direction, spark plug wires
magnetic field in coils compared to single wire left hand rule for coils thumb points north
soft iron core in coils, lines of force increase several hundred times
Solenoid can be used to push or pull iron core if
off set will be drawn into the middle
Battery Electro Chemical Device
4 functions 1. provides electrical energy to start car. 2. provides electrical energy to ignition system 3. provides electrical energy to accessories when
demands exceed alternators output 4. voltage stabilizer absorbs abnormal voltages
created by electrical components
Top postTop post Side post Side post
side and side and top posttop post
A side and top post is becoming very A side and top post is becoming very common today because it will fit so common today because it will fit so many cars.many cars.
Batteries a little history
Up to 1955 most batteries were 6 volt General Motors started the move to 12
volts, Volkswagen was the last in 1966 to switch over.
By 2010 some cars may have a 42V/14V System. Several problems lie in wait such as cost of the components. Life of batteries & arcing between components.
Battery Construction Elements consist of two groups of
plates one more negative than positive plates
with insulated separators in between usually 9, 11, or 13 plates. 54, 66, or 78
total. case is made of hard rubber (rough
service) or plastic (light service)
one element in each cell, connected to the adjoining element, connected in series, each cell produces about 2.1 volts
case is divided into 6 cells (12.6 volts) case is divided into 3 cells (6.3 volts)
Electrolyte64% water 36% Sulfuric acid
H20-water 64% specific gravity 1.00 H2S04-sulfuric acid 36% specific gravity
1.835 - caution electrolyte 100% specific gravity 1.270
Charged positive plate negative plate
electrolyte H2S04
pb02 pblead peroxide lead
Discharge oxygen and hydrogen form water, lead and sulfate
form lead sulfate pbso4 H20 pbSo4
Charging send electrons through opposite way reversing the cycle
Sulfated plates refer to plates harden with lead sulfate
Slow long charge to correct sulfated plates sometimes can't
Little brown particles floating around can short out battery (flakes off of the sulfated plates )
Batteries can freeze if discharged H2O is water
Charging battery emits oxygen and hydrogen gas - can explode
To replace add distilled water
Battery types WET CHARGE shipped with electrolyte
must charged during storage DRY CHARGE shipped empty
manufacture gives forming charge dries the cell elements and seals it. If you keep moisture out it will remain fully charged for long time. When needed just add electrolyte
Group size Batteries come in many different group sizes. A
battery's group size simply determines it's length, width, height, and terminal configuration
Will have a number like group 75,78 or 24 or 24F, 26, 34
Battery capacity 1) Plate size, the case same size, plates
are different size Larger plates more amps
2) Number of plates 3) Amount of acid in electrolyte and
battery additives increase the sulfuric acid content of battery
Battery capacity rating Cold Cranking Amperes CCA most common
“Number of amperes load of battery will maintain at 0 degrees Fahrenheit for 30 seconds without battery voltage falling below 7.2 volts” (1.2 volts per cell)
Size of engine should be smaller than cold cranking ampere
Do not be misled by CA that’s just Do not be misled by CA that’s just cranking amps. It will give you a higher cranking amps. It will give you a higher reading but it misleads you because it is reading but it misleads you because it is tested at a higher temperature.tested at a higher temperature.
Cranking amps are the numbers of amperes a lead-acid battery at 32 degrees F (0 degrees C) can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12 volt battery).
Recommended Minimum Recommended Minimum battery sizebattery size
4-cylinder 400 CCA
6-cylinder 500 CCA
8-cylinder 575 CCA
Battery checking visual Inspection
Battery checking visual Inspection
Cracked or leaking caseliquid level, add water use distilled water preferred (No minerals) or ice melted out of a freezer
Voltage can discharge across top from post to post
Clean battery top and post and cables, battery hold downs
visual Inspection
Mix baking soda and water to clean batteries
Clean post and cable with a terminal brush or post cutter
Coat all connections with grease or use a spray like NOCO NCP-2 Battery corrosion spray
Cleaning The Battery
Battery leakage test Battery leakage test Voltmeter – lead at negative postVoltmeter – lead at negative post Voltmeter + lead drag across batteryVoltmeter + lead drag across battery
No voltage should be present anywhere if it No voltage should be present anywhere if it is clean the battery.is clean the battery.
Battery Open Circuit Voltage TestBattery Open Circuit Voltage Test Measure what the voltage is with the key off Measure what the voltage is with the key off
Find out it’s state of charge. It is a good Find out it’s state of charge. It is a good starting point, should be at least 12.66 voltsstarting point, should be at least 12.66 volts
12.66 = fully charged12.66 = fully charged 12.4 = 3/4 charged12.4 = 3/4 charged 12.2 = 1/2 charged12.2 = 1/2 charged 12.0 = 1/4 charged12.0 = 1/4 charged
Battery Terminals & BoltsBattery Terminals & Bolts Post or top terminalPost or top terminal Side terminalSide terminal L terminal used on importL terminal used on import MarineMarine
Terminal TestTerminal Test This is the first step.This is the first step. Take a voltmeterTake a voltmeter DVOM (Digital volt ohm DVOM (Digital volt ohm
meter)meter) Turn to DC VoltsTurn to DC Volts Hook up like picture on Hook up like picture on
next page.next page.
Terminal TestTerminal Test This is just a voltage drop test done on This is just a voltage drop test done on
the battery terminals. You must disable the battery terminals. You must disable the ignition and crank over the engine. the ignition and crank over the engine. Should be under .2 volts. Should be under .2 volts. Make sure you do both Make sure you do both terminals Positive & terminals Positive &
NegativeNegative
Battery Drain test
Battery Drain Key off Hook up a ammeter in series reading
should not exceed the following 77 older cars .01 amps, 10 ma
(milliamps) 78-85 .02 amps-.025 amps, 20-25 ma 1986 & newer .05 amps, 50 ma
Testing specific gravity Hydrometer check before adding water
fully charged battery should read 1.270 should not vary more than 50 points between cells if it does recharge and check again
Maintenance free batteries are sealed, cannot get into some. No way to add water or check specific gravity.
Charging batteries
Clean up first Unhook cables - check liquid level Don't charge over 16 volts if plates are
sulfated or if battery has been discharged for some time
Slow charge for a long period 24 hoursdon't allow temperature to exceed 100
Never fast charge batteries
Most batteries in cars are 12 volt with negative ground.
6 volt older cars and 18 wheelers may have positive ground
SAFETY: do not allow battery acid to contact eyes skin or fabrics if you do flush with lots of water, and get teacher or medical help flush eyes for 15 minutes
Jump starting cars positive to positive negative to negative Hook up negative cable last on car with
dead battery on a good ground. Not on the battery. If sparks occur no Hydrogen to blow up
battery date tags
Did You Know Batteries Lose PowerDid You Know Batteries Lose Power While Sitting on the Shelf? While Sitting on the Shelf?
A battery can permanently lose some of its capacity when it's stored in a partly or fully discharged state. Periodic charging during storage can minimize the deterioration, but not all battery distributors and dealers do the necessary charging. That's why you may want to know how to read the date codes, which show when the product was manufactured, on a new product, to help you make sure you're really buying a fresh battery.
So, how do you read a date code?
Most Brands of BatteriesJOHNSON CONTROLS, INC. - INTERSTATE BATTERIES, Motorcraft, East penn - Deka, GNB -Champion, Stowaway:
The letters and numbers are on a sticker affixed to the battery or hot-stamped into the case cover along the top edges of the battery. The ship date codes begin with a letter: A stands for January, B for February and so on (some shipping codes skip the letter I, so it cannot be confused with the number 1. In those cases, J would represent September, K - October, L - November and M - December). The next digit is a number which represents the year the battery was shipped. Therefore, an A6 would mean the battery was shipped in January of 1996.
Exceptions DELCO - Freedom, Voyager, and some Sears brands:The code dates are stamped on the cover, usually near the posts. The first character represents the year (0-9) and the second shows the month (A-M, skipping I). For example, 4CN1 would stand for 1994, March.
EXIDE - Napa Legend, Edge, Power-Tron and Titan:
The fourth or fifth character may be a letter code for the month and the following character a number code for the year (i.e. RO8F3B stands for June 1993)
Last 3 pages © 2000 Interstate Battery System of America, Inc.
Always Disconnect the ground cable first. (Negative Cable on cars)
Always hook up the ground cable last
If you disconnect the positive first and touch ground you will have sparks.
Removing Batteries
Hooking batteries in series Voltage goes up
Hooking batteries in parallel Voltage stays the same amperage goes up
GeneratorGenerator Electromagnetic device, produces
electricity to run accessories and charge battery
If wire is passed through magnetic field voltage is generated
If passed in the opposite directioncurrent flow reversed
To increase volts and amps 1. increase strength of magnetic field 2. increase the speed wire moves
through the magnetic field
Basic AC operation current flows positive, negative
Basic DC operation
Current flows one way, accomplished by split ring
Charging Indicators ammeter
indicator light
Voltage Monitor
Alternator
Alternators
More efficient at lower speeds Lighter - aluminum construction Requires only 2 or 3 amps passing
through slip rings compared to high amperage in D.C. generator
Governs its own maximum current output
Alternator Generators - moving conductor through
stationary field to induce voltage Alternator - a permanent magnet is rotated
inside a stationary conductor
maximum voltage occurs when conductor cuts heaviest lines of force
Parts of a Alternator
The EndThe End
Pictures from SalsIllustrations from ChryslerScanned images from ModernAutomotive Technology and John Deere
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