Automotive Electrical Notes
PHS Auto 2
Basic notes for auto shop class
study and refer back to your text book
Electron theory

the electrical phenomenon is produced
by a flow of electrons from one area to
another.
Flow of electrons

The flow of electrons is caused by
having an excess number in one area,
shortage in another
surplus negative
short supply positive
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 Circuit

Parallel circuit, more than one path for
current to flow, current flows through all
units at once.
Parallel Circuit

Series parallel, combination of both
circuits.
Series Parallel
Circuit 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 = IxR
I = E/ R
R = E/ I
E
IXR
Ohms laws For Auto Techs
Some Auto Techs will use the following
 Amperes = A - Amps
 Volts
= V - Volts
 Ohms
= R - Resistance


to find
V = AxR
A = V/ R
R = V/ A
V
AXR
M, m, K, μ
Prefix
Symbol
Factor
Numerically
Name
giga
G
109
1 000 000 000
billion
Mega
M
106
1 000 000
million
kilo
k
103
1 000
thousand
centi
c
10-2
0.01
hundredth
milli
m
10-3
0.001
thousandth
micro
μ
10-6
0.000 001
millionth
nano
n
10-9
0.000 000 001
billionth
Magnetism
Materials that have this are called Magnets
 Some are Natural
 Some 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 post
Side post
side and
top post

A side and top post is becoming very
common today because it will fit so
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)

Electrolyte
64% 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
pb
lead 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
cranking amps. It will give you a higher
reading but it misleads you because it is
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
battery size

4-cylinder 400 CCA

6-cylinder 500 CCA

8-cylinder 575 CCA
Battery checking visual
Inspection
Battery checking visual
Inspection
Cracked or leaking case
liquid 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
Cleaning The Battery
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

Battery leakage test
Voltmeter – lead at negative post
 Voltmeter + lead drag across battery


No voltage should be present anywhere if it
is clean the battery.
Battery Open Circuit Voltage Test





Measure what the voltage is with the key off
Find out it’s state of charge. It is a good
starting point, should be at least 12.66 volts
12.66 = fully charged
12.4 = 3/4 charged
12.2 = 1/2 charged
12.0 = 1/4 charged
Battery Terminals & Bolts
Post or top terminal
 Side terminal
 L terminal used on import
 Marine

Terminal Test
This is the first step.
 Take a voltmeter
 DVOM (Digital volt ohm
meter)
 Turn to DC Volts
 Hook up like picture on
next page.

Terminal Test

This is just a voltage drop test done on
the battery terminals. You must disable
the ignition and crank over the engine.
Should be under .2 volts.
Make sure you do both
terminals Positive &
Negative
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 hours
don'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 Power
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 Batteries
JOHNSON 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.
Removing Batteries
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.
Hooking batteries in series
Voltage goes up
Hooking batteries in parallel
Voltage stays the same
amperage goes up
Generator

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 direction
current 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 End
Pictures from Sals
Illustrations from Chrysler
Scanned images from Modern
Automotive Technology and
John Deere