Automotive Electrical Systems 1
Electrical Circuits Contain 4 main parts 1. Power source battery alternator 2. Load 3. Control 4. Path 2
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Batteries What is a Battery? An electrochemical device which stores chemical energy and converts it to electrical energy on demand Purpose: Provides current for starting, ignition and accessories. Automotive batteries are a Lead-acid type Anode: Cathode: Lead Lead dioxide Electrolyte: Diluted Sulfuric Acid 4
Battery Ratings: Cold Cranking Amps (CCA) The number of amperes that can be supplied by a battery at 0 F (-18 C) for 30 seconds and still maintain a voltage or 1.2 V per cell or higher (7.2 V for a 12 Volt battery and 3.6 V for a 6 Volt battery) Reserve Capacity The number of minutes the battery can produce 25 A and still have a battery voltage of 1.75 V per cell (10.5 Volts) This rating is actually a measurement of the time a car can be driven in the event of a charging system failure. Amp-Hour Rating Determined by discharging a fresh, fully charged battery at a constant rate so selected that at the end of 20 hours, the voltage will have fallen to 1.75 V per cell (10.5 V in a 12 V battery) This discharge current, times 20 hours, gives the battery s amp-hour rating 5
Battery Main Components: Case Caps Positive Plates Negative Plates Electrolyte Separators Terminals 6
Battery Electrolyte: React chemically with positive & negative plates to produce electron flow Composition: 36% Sulphuric Acid H 2 SO 4 64% Water H 2 O Mixed by weight 7
Battery Plates: Positive Plates: Has a lack of electrons (positive charge) Negative Plates: Has an abundance of electrons (negative charge) 8
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Battery Separators: Prevent positive and negative plate groups from contacting Made from treated wood, glass fiber, porous rubber 10
Battery Cells: A fully charged 12V battery contains 12.6V WHY??? It contains 6 cells each producing 2.1V of electricity 11
Connecting / Disconnecting a Battery Which cable gets disconnected first??? NEGATIVE Which cable gets connected first??? POSITIVE DISCONNECT NPPN CONNECT 12
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Battery Tests: 1 Visual Cracks, bulges, dirt, leaks, corrosion 2 Hydrometer test (specific gravity) Full charge 1.260 1.280 ¾ charge 1.230 1.250 ½ charge 1.200 1.220 ¼ charge 1.170 1.190 Very Weak 1.140 1.160 Discharged 1.110 1.130 Maximum variation.050 3 Capacity (Load) Test 14
Specific Gravity: Determines the density of a liquid Water 1.000 Sulfuric Acid 1.835 Electrolyte 1.280 Condition of Battery Specific Gravity of Electrolyte When Electrolyte Freezes (Temp.) (F ) (C ) Discharged 1.100 +18-8 1.140 +8-13 1.180-6 -21 1.220-31 -35 Fully-Charged 1.260-75 -59 15
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Load (capacity) Test: 3 x Amp hour Rating or ½ Cold Cranking Rating for 15 seconds Voltage should not drop below 9.6 volts 3 Minute Fast Charge Test: 35 40 amps for 3 minutes Maximum voltage reading should not exceed 15.5 volts 17
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Starting Systems Starting Systems Motor Operating Principles A) A single wire is placed in a loop between two different magnetic poles B) Current flow in the loop creates a magnetic field C) Opposing magnetic fields between the wire and the permanent magnets causes the loop to rotate D) Once the loop rotates 180 degrees the current is reversed in the loop thought the brushes and continues to flip E) Adding more loops increases power F) Use of electricity to create a Field
Starting Systems Starting Systems Starter Motor Parts A) armature B) commutator C) brushes D) Field Magnets
Starting Systems Starting Systems Motor Operating Principles Rules of electricity related to Magnetism? #1 Unlike Poles (North &South) Attract! Like Poles Repel! #2 A moving magnet passing a wire in a complete circuit creates electron movement in that wire ( Electricity ) Factors that determine the amount of electrical current created -Speed of the moving magnetic field -Strength of the magnetic field - Size and type of conductor #3 Electron Flow in a wire creates a magnetic field around that wire (Electro Magnets)
Starting Systems Starting Systems Making the Starter Work! A) Starter Solenoid B) Starter Final Drive
Starting Systems Starting Systems Starter Curcuit
Alternators 24
Alternators Belt Driven Creates Current to run electrical systems when the vehicle is running Charges the battery when vehicle is running Battery should show a voltage of 13 15 Volts when vehicle is running 25
Charging Systems Charging Systems Alternator basics A) A spinning magnetic (engine driven) within a loop creates current flow in the wire B) Every 180 degrees of magnet rotation causes the current flow to reverse ( AC Current) C) Instead of a permanent magnet an electro magnet is used, this allows current flow to determine the strength of the magnetic field D) Slip rings allow current flow to maintain the same direction into the electro magnet (rotor) E) Instead of one loop of wire, there are many (stator)
Charging Systems Charging Systems Regulators A) Determine the amount of current required to operate the system (Load) B) Determine the state of charge of the battery C) Regulate the amount of electricity to the rotor to get an output D) Activate a light for the driver or show charging on a ammeter E) To stop overcharging
Charging Systems Charging Systems Problems 1) Low Battery a) start and stop driving d) battery will not accept a charge b) Accessories left on e) defective connections c) Loose drive belt f) defective alternator or regulator 2) Overcharged Battery a) short in stator field b) defective regulator 3) Faulty indicator lamp action a) defective wiring b) defective alternator or regulator 4) Noise a) worn bearings b) loose mountings c) worn belt drive
Connecting Jumper Cables Proper order is important so that there is no chance of an explosion from the battery 1 2 4 Engine or Frame Ground 3 29
Batteries, Starting & Charging Systems! Demo! Testing with a VAT (Voltage Amperage Tester ) 400 A)Battery Load Testing B)Starter Draw Test C) Alternator Output Test