1. Modern Automotive Technology PowerPoint for by Russell Krick
Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

2. Chapter 38
Hybrid Drive System
Operation and Repair

3. Contents Introduction to Hybrids Hybrid System Voltages
Hybrid Drive Assemblies
Hybrid Service Safety
Hybrid Problem Diagnosis
Hybrid Battery Pack Service
(Continued)

4. Contents Checking HV Battery Relays and Contactors
Servicing Hybrid Power Cables
Servicing the Power Control Module
Servicing the Hybrid Cooling System
Servicing the Motor-Generator
Hybrid Wiring Problems

5. Introduction to Hybrids
Hybrid vehicles (HVs) use two individual power sources to provide energy for propulsion
internal combustion engine
electric drive system

6. Introduction to Hybrids
Hybrid gas-electric vehicles (HGEVs) are currently produced
Others are in development:
fuel cell hybrid
hydraulic hybrid
pneumatic hybrid

7. Introduction to Hybrids
Hybrids can be identified in two ways
Badging on the front fender, engine cover, or hood
The 5th, 6th, and 7th alphanumeric characters in the VIN

8. Hybrid Vehicle History
In 1898, Ferdinand Porsche built a gas-electric hybrid
small internal combustion engine to spin a large generator
drive motors at each wheel
same concept is used in modern locomotives

9. Hybrid Drive Vehicle
In a gas-electric hybrid, the engine and electric drive system work together
There are six major components:
high-voltage battery pack
motor-generator
power control module
hybrid drive ECU
power cables
internal combustion engine

10. Hybrid Types Full hybrid uses a motor-generator for propulsion
uses an internal combustion engine to drive the generator to recharge the battery pack

11. Hybrid Types Mild hybrid propelled by an internal combustion engine
engine shuts off during braking, coasting, and stops
high-powered starter-alternator restarts the engine when brakes are released
electric motors drive accessory items so they are available when the engine is off

12. Hybrid Drive Train Configurations
Series hybrid
Parallel hybrid
Series/parallel hybrid

13. Series Hybrid Separate generator and traction motor(s)
Engine drives the generator; separate traction motors propel the vehicle
No mechanical connection between the engine and drive train

14. Series Hybrid

15. Parallel Hybrid Engine and motor-generator can both propel the vehicle
Functions as a standard gasoline-powered vehicle for hard acceleration and high-speed operation
Functions as an all-electric vehicle for city driving
Motor-generator can switch between charging and propulsion, but cannot do both simultaneously

16. Parallel Hybrid

17. Series/Parallel Hybrid
Separate generator and traction motor(s)
Combines the advantages of parallel and series hybrids
Engine can propel the vehicle and drive the generator to change the battery pack at same time
Power splitter is used to transfer engine and electric motor power through the drive train

18. Series/Parallel Hybrid

19. Hybrid Vehicle Operation
Five modes of operation
all-electric drive
motor assist
idle stop
regenerative braking
engine starting

20. All-Electric Drive Mode
Battery pack provides all energy needed to propel the vehicle
Many hybrids stay in all-electric mode when accelerating up to mph
When a hybrid runs on electrical energy only, it burns no fuel and emits no hydrocarbons

21. The engine is off, and the motor-generator propels the vehicle
All-Electric Mode
The engine is off, and the motor-generator propels the vehicle

22. Motor Assist Mode
Both the motor-generator and internal combustion engine apply torque to the drive train for propulsion

23. The engine and motor-generator work together to propel the vehicle
Motor Assist Mode
The engine and motor-generator work together to propel the vehicle

24. Idle Stop Mode
Internal combustion engine is shut off when the vehicle comes to a stop
The engine restarts when the vehicle reaches a predetermined speed or when the battery pack is discharged

25. Regenerative Braking Mode
When brakes are applied, the motor-generator functions as a generator
The drag created by the generator slows the vehicle and recaptures the vehicle’s kinetic energy
Hydraulic brakes are applied only for hard braking

26. Regenerative Braking Mode
Motor-generator slows the vehicle while generating electricity

27. Engine Starting Mode Hybrid ECU:
energizes transmission solenoids to lock the motor-generator and engine together
sends just enough current to the motor-generator to turn the engine at about rpm
signals the engine ECU to provide spark and fuel to the engine

28. Battery Pack Charging Mode
When the hybrid ECU detects low battery pack charge, it restarts the engine to propel the vehicle and recharge the battery pack

29. Battery Recharging Mode
Engine drives the motor-generator to recharge the battery pack

30. Hybrid System Voltages
Hybrids use two voltage systems, wired separately but interfaced through the ECU and power control module
high-voltage system
low-voltage system

31. High-Voltage System
Operates on voltages ranging from 250–650 volts ac or dc
hybrid drive and charging circuits
Hybrid nominal output voltage
maximum dc voltage available from battery pack
typically 100 to more than 300 volts
Hybrid maximum voltage
the 3-phase ac voltage fed to the motor-generator from the power control module
up to 650 volts ac

32. Low-Voltage System Uses conventional 12-volt battery
Maintains computer memory
Provides low voltage to electrical accessories and low-voltage electrical engine components
fuel injectors
ignition coil
sensors

33. Hybrid Drive Assemblies
Battery pack
Motor-generator
Power control module
Hybrid drive ECU
Power splitter
Hybrid power cables
Numerous switches, relays, fuses, connectors, and sensors
Cooling system

34. Battery Pack
Several high-efficiency nickel metal hydride (NiMH) battery modules
Stacked in a sealed enclosure
Wired in series for high voltage

35. Battery Pack
Designed to handle very high current flow rates during battery discharge
Very good weigh-to-power ratio
Voltage can range from volts dc
Sensors monitor cell temperature
If a battery problem exists, the hybrid ECU will light a warning light on the dash and shut down the electric drive system

36. Motor-Generator
Functions as both a powerful traction motor and a high-energy alternator
helps propel the vehicle
recharges the HV battery pack
cranks the internal combustion engine
helps slow and stop the vehicle
Construction is similar to other motors and alternators
consists of armature, stator, and housing
armature spins in close proximity to the stator

37. Motor-Generator Construction
The typical motor-generator uses permanent magnets in the armature and electromagnets in the stator

38. Motor-Generator as a Motor
Permanent magnet design improves reliability
3-phase ac current energizes stator
sets up a 3-wave magnetic field that moves around the stator, pushing and pulling the armature with it
more horsepower and torque and better efficiency than equivalent dc motor
torque is controlled by current flow
speed is controlled by frequency and phase shift of ac waves

39. Motor-Generator as a Generator
Functions as a generator when the battery becomes discharged and during regenerative braking
Internal combustion engine or drive train spins the motor generator’s permanent magnet armature
armature’s magnetic fields pass through stator windings
induces ac current in the stator windings

40. Single Motor-Generator Hybrid
The least complex hybrid drive configurations use a single motor-generator

41. Dual Motor-Generator Hybrid
The dual motor-generator configuration is capable of simultaneously propelling the vehicle and recharging the battery pack

42. Triple Motor-Generator Hybrid
Triple motor-generator arrangements are used in all-wheel and four-wheel drive hybrids

43. Power Control Module
Alters current and routes it between the HV battery pack and motor-generator
Converter circuit steps dc voltage up or down
Inverter circuit changes dc to 3-phase ac or 3-phase ac to dc
Motor-generator ECU controls the converter and inverter circuits to efficiently operate the motor-generator(s)

44. Power Control Module
Two wires run from the power control module to the battery pack; three wires run from the power control unit to the motor-generator

45. Battery Relays and Contactors
Control the flow of electricity between the battery pack and the power control module
When the ignition key is off
battery relays and contactors are open
no current can flow to the power control module and motor-generator

46. Battery Relays and Contactors
When the ignition key is turned to run
battery relays close and energize contactor coils
contactor closes
circuit is completed between battery pack and power control module

47. Hybrid Drive ECU Controls the power control module and motor-generator
keeps the HV battery pack operating at optimum temperature and state of charge
Receives input from pedal position and other sensors
uses sensor input data to determine the proper operating mode for the motor-generator

48. Power Splitter
Planetary gearset used to transfer power through the hybrid drive train
solenoids apply and release friction members to control the planetary gearset
can control flow of torque from both the internal combustion engine and the motor-generator(s)
Power splitter and drivetrain are under computer control

49. Hybrid Power Cables
Heavily insulated cables transfer extremely high voltages
Two cables connect power control module to the battery pack
Three cables connect the power control module to the motor-generator
orange insulation for easy identification

50. High-Voltage Circuit Protection
Ground fault interrupter
constantly monitors the system for high-voltage leakage into the chassis
illuminates a warning light and opens power relays if high voltage from the battery pack or motor-generator shorts to ground
High-voltage fuse
permanently burns open if current in the circuit is too high

51. Sensors Impact sensors Motor-generator sensor
open the high-voltage circuits, disable the fuel pump, and deploy airbags in a severe impact
Motor-generator sensor
detects the speed and position of the motor-generator armature

52. Hybrid Drive Cooling Water cooling
circulates engine coolant through the transaxle, motor generator(s), and power control module
carries heat to the radiator
many hybrids have two radiators: one conventional and one for the hybrid drive system

53. Hybrid Drive Cooling Air cooling Refrigerant cooling
uses an electric blower to circulate air through the battery pack enclosure
Refrigerant cooling
circulates R-134a refrigerant through an evaporator next to the battery pack or PCM

54. Hybrid Dash Display
Combination meter comprises numerous individual gauges and displays hybrid drive operating conditions

55. Hybrid Dash Display
Hybrid power display informs the driver about how electrical energy is being used and how much charge remains in the battery pack
Hybrid drive ready light glows continuously when the vehicle is ready to be driven
Hybrid master warning light indicates problems in the drivetrain
Battery pack warning light indicates low charge in the battery pack

56. Hybrid Service Safety
Hybrids generate and store enough electrical energy to cause electrocution
Safe work habits are extremely important when working on hybrids

57. Hybrid Safety Precautions
Remove all jewelry before working on a hybrid’s high-voltage circuits
high voltage can arc through air and into jewelry
Wear insulating gloves
use OSHA-approved lineman’s gloves rated at 1000 volts or better
before working, check gloves for leaks

58. Hybrid Safety Precautions
Wear rubber-soled shoes
Keep a fire extinguisher nearby
make sure extinguisher is suitable for electrical fires (class C)
When towing, raise any wheels connected to drive motors
Turn the ignition key off and disconnect the 12v battery to disable drive before working

59. Hybrid Safety Precautions
Move metal equipment out of the work area to avoid accidental electrocution
Use the high-voltage disconnect to physically disconnect the battery pack from the power control module
wait at least five minutes after disconnection to begin work

60. Hybrid Problem Diagnosis
Onboard diagnostics monitor hundreds of operating conditions and turn on a warning light if a problem is detected
Use a scan tool to retrieve codes if a malfunction indicator light is glowing
Hybrid drive troubles are assigned specific codes

61. Hybrid Battery Pack Service
Hybrid battery packs have a warranty from the vehicle manufacturer
Battery packs are very dependable, though electrolyte and plates can be depleted after many years of operation
NiMH batteries should not be stored for long periods

62. Battery Pack Recharging
Hybrid battery charger uses a step-up transformer to force high-voltage into the battery pack
battery packs that fail to take a full charge should be replaced

63. Battery Pack Recharging
If the vehicle has a conventional 12-volt battery, it can usually be jump-started with booster cables
never try to jump-start an HV battery pack with a 12-volt booster battery, or the battery will explode

64. Battery Pack Testing
To check battery pack performance, connect a scan tool and test-drive the vehicle
use regenerative braking and drive uphill to place demands on the system
the combination meter and scan tool will indicate the battery pack’s state of charge, battery voltage, and recharge current

65. Battery Pack Testing
compare results to known good battery pack or manufacturer’s specifications
if the battery pack does not hold charge, produces insufficient current, or has poor capacity, it should be replaced

66. Battery Pack Testing
If high battery temperatures are indicated, use an infrared thermometer to compare cell temperatures
if only one cell runs warm, it is probably shorted and the battery pack should be replaced
if all cells are warm, check cooling system
Check for problems in an air cooling system
blower electrical or mechanical problems
damaged or blocked air intake ducts

67. Battery Pack Replacement
Battery packs are usually located in the trunk or under the rear seat cushion or floor pan
Most common reason for replacement is damage from a collision
Be careful removing a battery pack
wear insulated rubber gloves and eye protection
use an assistant or an engine hoist to lift the battery pack
place high-voltage warning labels on the shipping container

68. Checking HV Battery Relays
and Contactors
Check should be done if trouble codes indicate that the battery is OK, but power is not reaching the power control module
Contactor lugs can become burned and pitted

69. Checking HV Battery Relays
and Contactors
If burned, contactor lugs will develop increased resistance and may not deliver sufficient current to the PCM
When measuring high voltage, use only high-voltage meter with leads having thick insulation

70. Servicing Hybrid Power Cables
Check resistance values of cables in the scan tool’s data list display
if resistance is too high, tighten or repair cable ends, or replace cables if needed
If the scan tool reading indicates a ground fault, perform an ohmmeter test between cable connector and ground
if resistance is too low (<350k ohms), the cable may be shorting to ground

71. Servicing Hybrid Power Cables
A loose cable end can overheat and burn the electrical connection
Always torque cable fasteners to factory specs

72. Checking Cable for Voltage Leak
If resistance between the cable connector and ground is too low, voltage may be leaking

73. Servicing the Power Control Module
Common problems
circuit board failure
faults caused by overheating
Some hybrids use a separate power converter
if scan tool indicates an internal converter problem, the converter should be removed and replaced

74. Servicing the Hybrid Cooling System
If the system is air cooled, listen for normal cooling fan operation
if the blower motor is bad, replace it the way you would a climate control blower
disconnect ducts and wiring before removing the fasteners securing the blower

75. Servicing the Hybrid Cooling System
If the system is liquid cooled, use a stethoscope to listen to pump operation
ensure the pump operates during high electrical load conditions

76. Servicing the Motor-Generator
Coil windings can short or burn open
scan tool will show code
combination gauge will indicate poor performance during all-electric mode and regenerative braking

77. Servicing the Motor-Generator
Follow manufacturer’s procedures for replacing the motor-generator or its components
a plastic sleeve may be inserted between the stator and armature to prevent contact
make sure the work area is clean and free of iron filings and other debris

78. Hybrid Wiring Problems
If scan tool indicates a problem in a particular component but the component tests good, check the wiring
use factory wiring diagrams
locate and check connectors and other components that could be affecting the circuit