© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only

Publisher

The Goodheart-Willcox Co., Inc.Tinley Park, Illinois

by

Russell Krick



Introduction to Hybrids Hybrid System Voltages Hybrid Drive Assemblies Hybrid Service Safety Hybrid Problem Diagnosis Hybrid Battery Pack Service

(Continued)


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


Hybrid vehicles (HVs) use two individual power sources to provide energy for propulsioninternal combustion engineelectric drive system


Hybrid gas-electric vehicles (HGEVs) are currently produced

Others are in development:fuel cell hybridhydraulic hybridpneumatic hybrid


Hybrids can be identified in two waysBadging on the front fender, engine

cover, or hoodThe 5th, 6th, and 7th alphanumeric

characters in the VIN


Hybrid Vehicle History In 1898, Ferdinand Porsche built a gas-

electric hybridsmall internal combustion engine to spin

a large generatordrive motors at each wheelsame concept is used in modern

locomotives


Hybrid Drive Vehicle In a gas-electric hybrid, the engine and

electric drive system work together There are six major components:

high-voltage battery packmotor-generatorpower control modulehybrid drive ECUpower cables internal combustion engine


Hybrid Types Full hybrid

uses a motor-generator for propulsionuses an internal combustion engine to

drive the generator to recharge the battery pack


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


Hybrid Drive Train Configurations

Series hybrid Parallel hybrid Series/parallel hybrid


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


Series Hybrid


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


Parallel Hybrid


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


Series/Parallel Hybrid


Hybrid Vehicle Operation

Five modes of operationall-electric drivemotor assistidle stopregenerative brakingengine starting


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 20-40 mph

When a hybrid runs on electrical energy only, it burns no fuel and emits no hydrocarbons


All-Electric Mode

The engine is off, and the motor-generator propels the vehicle


Motor Assist Mode

Both the motor-generator and internal combustion engine apply torque to the drive train for propulsion


Motor Assist Mode

The engine and motor-generator work together to propel the vehicle


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


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


Regenerative Braking Mode

Motor-generator slows the vehicle while generating electricity


Engine Starting Mode

Hybrid ECU:energizes transmission solenoids to lock

the motor-generator and engine togethersends just enough current to the motor-

generator to turn the engine at about 300 rpm

signals the engine ECU to provide spark and fuel to the engine


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


Engine drives the motor-generator to recharge the battery pack

Battery Recharging Mode


Hybrids use two voltage systems, wired separately but interfaced through the ECU and power control modulehigh-voltage systemlow-voltage system


High-Voltage System Operates on voltages ranging from 250–650

volts ac or dchybrid drive and charging circuits

Hybrid nominal output voltagemaximum 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 moduleup to 650 volts ac


Low-Voltage System

Uses conventional 12-volt battery Maintains computer memory Provides low voltage to electrical

accessories and low-voltage electrical engine componentsfuel injectorsignition coilsensors


Battery pack Motor-generator Power control

module Hybrid drive ECU Power splitter

Hybrid power cables Numerous switches,

relays, fuses, connectors, and sensors

Cooling system


Battery Pack

Several high-efficiency nickel metal hydride (NiMH) battery modulesStacked in a sealed

enclosureWired in series for high

voltage


Battery Pack

Designed to handle very high current flow rates during battery discharge

Very good weigh-to-power ratio Voltage can range from 150-300 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


Motor-Generator Functions as both a powerful traction motor

and a high-energy alternatorhelps propel the vehicle recharges the HV battery packcranks the internal combustion enginehelps slow and stop the vehicle

Construction is similar to other motors and alternatorsconsists of armature, stator, and housingarmature spins in close proximity to the stator


Motor-Generator Construction

The typical motor-generator uses permanent magnets in the armature and electromagnets in the stator


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 flowspeed is controlled by frequency and phase shift

of ac waves


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


Single Motor-Generator Hybrid

The least complex hybrid drive configurations use a single motor-generator


Dual Motor-Generator Hybrid

The dual motor-generator configuration is capable of simultaneously propelling the vehicle

and recharging the battery pack


Triple Motor-Generator Hybrid

Triple motor-generator arrangements are used in all-wheel and four-wheel drive hybrids


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)


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


Battery Relays and Contactors

Control the flow of electricity between the battery pack and the power control module

When the ignition key is offbattery relays and contactors are openno current can flow to the power control

module and motor-generator


Battery Relays and Contactors

When the ignition key is turned to runbattery relays close and energize

contactor coilscontactor closescircuit is completed between battery pack

and power control module


Hybrid Drive ECU

Controls the power control module and motor-generatorkeeps the HV battery pack operating at

optimum temperature and state of charge Receives input from pedal position and

other sensorsuses sensor input data to determine the

proper operating mode for the motor-generator


Power Splitter

Planetary gearset used to transfer power through the hybrid drive trainsolenoids apply and release friction

members to control the planetary gearsetcan control flow of torque from both the

internal combustion engine and the motor-generator(s)

Power splitter and drivetrain are under computer control


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-generatororange insulation for easy identification


High-Voltage Circuit Protection

Ground fault interrupterconstantly monitors the system for high-

voltage leakage into the chassisilluminates a warning light and opens power

relays if high voltage from the battery pack or motor-generator shorts to ground

High-voltage fusepermanently burns open if current in the

circuit is too high


Sensors

Impact sensorsopen the high-voltage circuits, disable the

fuel pump, and deploy airbags in a severe impact

Motor-generator sensordetects the speed and position of the

motor-generator armature


Hybrid Drive Cooling Water cooling

circulates engine coolant through the transaxle, motor generator(s), and power control module

carries heat to the radiatormany hybrids have two radiators: one

conventional and one for the hybrid drive system


Hybrid Drive Cooling Air cooling

uses an electric blower to circulate air through the battery pack enclosure

Refrigerant coolingcirculates R-134a refrigerant through an

evaporator next to the battery pack or PCM


Hybrid Dash Display

Combination meter comprises numerous individual gauges and displays hybrid drive operating conditions


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


Hybrids generate and store enough electrical energy to cause electrocution

Safe work habits are extremely important when working on hybrids


Hybrid Safety Precautions

Remove all jewelry before working on a hybrid’s high-voltage circuitshigh voltage can arc through air and into

jewelry

Wear insulating glovesuse OSHA-approved lineman’s gloves

rated at 1000 volts or betterbefore working, check gloves for leaks



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



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 modulewait at least five minutes after

disconnection to begin work


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


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


Battery Pack Recharging

Hybrid battery charger uses a step-up transformer to force high-voltage into the battery packbattery packs that fail to take a full charge

should be replaced


Battery Pack Recharging

If the vehicle has a conventional 12-volt battery, it can usually be jump-started with booster cablesnever try to jump-start an HV battery pack

with a 12-volt booster battery, or the battery will explode


Battery Pack Testing

To check battery pack performance, connect a scan tool and test-drive the vehicleuse regenerative braking and drive uphill

to place demands on the systemthe combination meter and scan tool will

indicate the battery pack’s state of charge, battery voltage, and recharge current



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



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 systemblower electrical or mechanical problemsdamaged or blocked air intake ducts


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 packwear insulated rubber gloves and eye protectionuse an assistant or an engine hoist to lift the

battery packplace high-voltage warning labels on the

shipping container


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


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


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 groundif resistance is too low (<350k ohms), the

cable may be shorting to ground


A loose cable end can overheat and burn the electrical connection

Always torque cable fasteners to factory specs


Checking Cable for Voltage Leak

If resistance between the cable connector and ground is too low, voltage may be leaking


Common problemscircuit board failurefaults caused by overheating

Some hybrids use a separate power converterif scan tool indicates an internal converter

problem, the converter should be removed and replaced


If the system is air cooled, listen for normal cooling fan operationif the blower motor is bad, replace it the

way you would a climate control blowerdisconnect ducts and wiring before

removing the fasteners securing the blower


If the system is liquid cooled, use a stethoscope to listen to pump operationensure the pump operates during high

electrical load conditions


Coil windings can short or burn openscan tool will show codecombination gauge will indicate poor

performance during all-electric mode and regenerative braking


Follow manufacturer’s procedures for replacing the motor-generator or its componentsa 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


If scan tool indicates a problem in a particular component but the component tests good, check the wiringuse factory wiring diagramslocate and check connectors and other

components that could be affecting the circuit

Documents

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois