1. Chapter 19
Charging Systems

2. Charging Systems Primary purpose is to recharge battery
Changes mechanical energy into electrical energy
Voltage is induced into a wire as it passes through a magnetic field
The voltage has positive and negative pulses

3. AC Generator Construction
Rotor assembly
Rotating magnetic field
4 .0 to 6.5 amps pass through coil
One pole piece assumes north and the other south polarity

4. Alternating Current Charging Systems

5. Slip Rings and Brushes
Regulated current supplied to rotor coil via slip rings and brushes

6. Stator
Most AC generators use three stator windings

7. Stator (Cont.)
Each stator conductor produces a single phase of AC current
The phases are staggered 120° apart

8. End Frame Assembly Contains rotor shaft bearings and air ducts
Rectifier diodes attached to end frame
Heat passes from diodes to air
Cooling fans pull air through generator
May have external or internal fans

9. Diodes with cooling fins
Rear driveshaft bearing

10. Liquid Cooled Generators
Water or coolant used to keep diode temperature down
Eliminates fans and reduces noise
Hoses connect generator to engine cooling system
Allows for increased output and longer generator life

11. AC Generator Operation
Produce alternating current
The AC must be converted, or rectified, into direct current, DC
The AC passes through diodes

12. Diodes

13. DC Rectification Using six diodes allows for full-wave rectification
Two diodes for each stator winding
One diode is positive, the other negative
The wye winding has a central neutral junction

15. Knowledge Check Describe how diodes are used to change AC into DC.
Diodes allow current to flow in one direction so by placing them with either a positive or a negative bias, the diodes can be used to block unwanted AC.

16. Factors Controlling Generator Output
Rotational speed of the rotor
Number of windings in the rotor
Current flow through rotor
Number of windings in the stator

17. Voltage Regulation
Output is controlled by varying current through the rotor
Resistance in series with the field coil
Sensing voltage allows the regulator to monitor system voltage
Temperature also monitored

18. Types of Field Circuits
“A” type
Has the regulator on the ground side of the field coil
“B” type
Has the regulator on the positive side of the field coil
Isolated field
The regulator can be on either the ground or the positive side

21. Types of Voltage Regulators
Electronic regulator
Can be internally or externally mounted
Uses a zener diode or pulse width modulation to control field current
Integrated circuit voltage regulators
Internally or externally mounted
Controls field current through a diode trio

22. Types of Voltage Regulators (Cont.)
Computer-controlled regulation
Is used on many late-model vehicles
The computer (PCM) uses battery voltage and temperature to determine voltage needs
Most systems use pulse width modulation to control field current

23. Pulse Width Modulation

24. Motor/Generators
Using electronic controls, a generator can work as a motor
Can be mounted external to the engine or mounted directly
Capable of high charging outputs
Can crank engine at high speeds

25. Motor/Generators (Cont.)
Capable of stop-start operation
Regenerative braking
Electrical assist

26. Regenerative Braking Braking energy used to recharge batteries
Motor/generator converts kinetic energy into electrical energy
A combination of conventional and regenerative braking used
Found on all hybrid vehicles

27. Regen

28. Knowledge Check Explain how the PCM controls generator output.
The PCM can pulse the voltage regulator very quickly on and off. This is called pulse-width modulation.

29. Preliminary Charging System Checks
Safety Precautions
Disconnect negative terminal
Avoid contact with generator output terminal
Only apply pressure to front of generator housing when applying belt tension
Observe correct polarity of battery cables
Keep carbon pile tester off at all times
Use caution around moving parts

30. Charging Indicators Indicator (charge) lamp Meters
Operates on the principle of opposing voltages
Meters
Voltmeter or ammeter display on dash
Electronic voltage monitor
Is used to monitor voltage and control a lamp or warning message

31. Charge Indicator Lamp

32. Inspection Inspect the battery Check wiring and connections
Inspect alternator mountings for loose or missing bolts
Check condition of the drive belt
Ensure proper pulley alignment

33. PCM-Controlled Systems
Check DTCs
Monitor voltage with scan tool
PCM monitors battery current, voltage, and temperature
May adjust idle speed to increase charging rate

34. Battery Current Sensor

35. Noise Diagnosis Noise can be mechanical or electrical
Some electrical noise is normal
Belts and bearings can produce noise
Check mounting, wiring, cooling and A/C hoses and lines for misrouting
Generator pulley should spin freely with belt removed

36. Regulator Tests
Excessive charging most likely caused by voltage regulator
Can also cause no output
Some systems can bypass regulator for full-field tests
Always follow manufacturer’s procedures

37. Voltage Regulator Test Point

38. Voltage Output Test Measure battery open circuit voltage
Run engine at fast idle (1500 rpm)
No load voltage should be about 2 volts higher than open circuit voltage
If low, increase speed to 2000 rpm and turn on accessories
Voltage should be about 0.5 volts above open circuit voltage

39. Current Output Test Run engine around 2500 rpm
Adjust carbon pile to maximum current output
Should be within 10 amps of rated output

40. AC Leakage Test
Connect DMM in series to charging output terminal with engine off
Reading should be no more than 0.5 mA

41. Oscilloscope Checks

42. Knowledge Check
A generator rated for 120 amp only produces 75 amps. Technician A says the voltage regulator may be faulty. Technician B says the diodes may be faulty. Who is correct?
Both Technician A and B

43. Circuit and Ground Resistance
Check voltage drop of charging output connection and ground circuit.
Test between battery positive and generator output terminal.
Test between battery negative and generator case.
Test under at least 20 amps output.

44. Voltage Drop Tests

45. Replacing a Generator Disconnect the battery negative connection.
Remove generator wiring and drive belt.
Remove the generator.
Compare new and old generator.
Install and torque fasteners.
Test the new generator.