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

Chapter 38 Hybrid Drive System Operation and Repair

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

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

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

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

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

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

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

Hybrid Types Full hybrid uses a motor-generator for propulsion uses 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 operation all-electric drive motor assist idle stop regenerative braking engine 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

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

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

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

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 together sends 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

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

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

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

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

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

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

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 flow speed 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 off battery relays and contactors are open no current can flow to the power control module and motor-generator

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

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

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

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

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

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

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

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

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

Hybrid Service Safety 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 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

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

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

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

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

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

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

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

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

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

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

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

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

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

Servicing Hybrid Power Cables 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

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

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

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

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

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

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