48-VOLT DEVELOPMENTSKevin Jost

HIGH-VOLTAGE DEVELOPMENTS Kevin Jost

Development of higher-voltage electrical systems in vehicles has been slowly progressing over the past few decades. However, tightening vehicle e� ciency and emissions regulations and increasing demand for onboard electrical power means that higher voltages, in the form of supplemental 48 V subsystems, may soon be nearing production as the most cost-e� ective way to meet regulations. The displacement of high-wattage loads to more e� cient 48 V networks is expected to be the next step in the development of a new generation of mild hybrid vehicles.In addition to improved fuel economy and reduced emissions, 48 V systems could potentially save costs on new electrical features and help better address the emerging needs of future drivers. Challenges to 48 V system implementation remain, leading to discussions by experts from leading car makers and suppliers on the need for an international 48 V standard. Initial steps toward a proposed standard have already been taken. So the consensus of global forecasts suggests that 48 V mild hybrids will soon come to dominate the market. Compared with 200-600 V full hybrid and battery electricvehicles, the lower-voltage approachavoids the need for high-cost safetyfeatures and large battery packs..

About the Author Kevin is currently the Editorial Director for SAE International’s Magazines, Books, Videos, and Intellectual Property in Warrendale PA. Prior

to that he served various editorial roles with SAE Magazines including Editor of Automotive Engineering and O� -Highway Engineering. His industry experience includes roles as fi rst Project Engineer for testing and then Product Engineer for seating and other trim systems at Lear Corp. in Southfi eld MI.

TU-002ISBN: 978-0-7680-8192-3

9 780768 081923

Jost48-VO

LT DEV

ELOPM

ENTS

AUTOMOTIVE

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Introduction ...........................................................................ix

Chapter 1 Fuel Consumption and Emissions Effects in Passenger Car Diesel Engines through the Use of a Belt Starter Generator .................................................................... 1

Drivetrain Architecture .....................................................................................2Methods ...............................................................................................................4

Thermodynamic Optimisation ................................................................4Automated Cycle Driving ........................................................................4Hybrid Operating Strategy .......................................................................7

Results and Discussion ....................................................................................14Conclusions .......................................................................................................19References ..........................................................................................................21

Chapter 2 Requirements and Protection within a 48V Automotive Wiring System ................................................. 23

Weight Saving Issues and Topology of a Multi-Voltage Wiring System ..24Operating Safety for the 48V Wiring System ...............................................25Protection Concepts for the Different Arc Types .........................................27Conclusions .......................................................................................................30

Chapter 3 Mixed Voltages and Aluminum Conductors: Assessing New Electrical Technologies ............................... 31

Integrating Flow for 48V System Components and Aluminum Wires ....32Build 48V Components into a 12V Vehicle System .............................32Verification of a Mixed Voltage System ................................................34Replacement of Copper with Aluminum Wires ..................................35Examine the Results of all Recommended Changes ...........................36

Summary ...........................................................................................................37References ..........................................................................................................37

Table of Contents

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Chapter 4 Hybrid Cars Setting New Challenges for Optimized Power Semiconductors ..................................... 39

The Variety of Battery Voltages for Plug-In Vehicles - xEVs ......................40Voltage Classes of the Semiconductors Tailored to the Application ........42

Simulation of a 12V ABS System ...........................................................42Simulation of a 12V Engine Cooling Fan ..............................................43Dc-dc Converter Simulation of 250V/400V .........................................44Summary ...................................................................................................45

Semiconductors Tailored to Different Voltage Classes ...............................46Conclusion ........................................................................................................51

Chapter 5 Specification and Design of a Switched Reluctance 48 V Belt Integrated Starter Generator (B-ISG) for Mild Hybrid Passenger Car Applications....................... 53

Electrical Implementation of 48V systems ...................................................54Vehicle Architecture Layouts ..........................................................................55

Small Vehicle Segment ............................................................................55Large Vehicle Segments...........................................................................56

Application Specific Motor Requirements ...................................................57Motor Design Challenges................................................................................58Traditional Switched Reluctance Machine Challenges ...............................61

Torque, Voltage and Current Ripple .....................................................61Noise, Vibration, and Harshness ...........................................................62Electronics Costs ......................................................................................63

Diverging Solutions with a Common Core ..................................................64Winding Variants .....................................................................................64Electronics Variants .................................................................................64Control Systems and Modelling Variants .............................................64

SpeedStart Performance Data.........................................................................65Energy Storage ..................................................................................................66Conclusions .......................................................................................................67References ..........................................................................................................68

Chapter 6 Optimizing Lithium-Ion Batteries - Tailoring Electrodes for Microhybrid Vehicle Applications............... 69

Experimental .....................................................................................................70Drive Cycles Used in this Work .............................................................70Vehicle Simulation ...................................................................................71Electrochemical Simulation ....................................................................72

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Results ................................................................................................................73Defining Metrics and Targets for Microhybrid ....................................73

Energy Density ...............................................................................74Power Density ................................................................................75Combining Fuel Economy and Volume .....................................76

Limiting Constraints for Electrode Sizing ............................................78Fundamental Limitation of Charge Acceptance .......................78Customizing Electrodes for Intended Life .................................79Varying Conditions Over Battery Life ........................................79Varying Vehicle-Level Requirements Over Battery Life ............80

Optimizing Electrodes for Microhybrid ...............................................82Customizing Electrodes for Cell Capacity .................................82Effects due to Motor/Generator Size .........................................84Customizing Electrodes for Drive Cycles ..................................84

Discussion .........................................................................................................86Analysis of the Whrecov/L Metric ............................................................86

Applicability of WHrecov/L Metric ...............................................86Variants of the Whrecov/L Metric ..................................................87

Impacts of Vehicle Requirements ..........................................................87Definition of Battery Life ..............................................................87Vehicle Architecture Changes ......................................................88

Drive Cycle Impacts ................................................................................89Summary and Conclusions .............................................................................89

Impact of Quantitative Optimization ...................................................89Other Vehicle Applications .....................................................................89

References ..........................................................................................................90

Chapter 7 Application of 48 Volt for Mild Hybrid Vehicles and High Power Loads ......................................................... 93

Characteristics and Requirements of the 48V E/E System ........................94Failure Modes in the 14V/48V E/E System .................................................95

Short to Ground .......................................................................................95Loss of Common Ground .......................................................................96Voltage Short Circuit ...............................................................................96Broken Wire ..............................................................................................97

Recommendations for 48V E/E System design .........................................100Battery Box ..............................................................................................100Power Distribution Boxes .....................................................................100

Pre-Fuse Boxes .............................................................................100Bused Electrical Centers .............................................................101

Electric/Electronic Centers (Smart E/E Centers) ...................101Electronic Modules (dc-dc converters) .....................................101

Wires for 48V Application ....................................................................101Routing .........................................................................................102Materials .......................................................................................102Color Coding ................................................................................102

Connection Systems for 48V Application ...........................................102Avoidance of Hot Plugging ..................................................................103

Component Level .......................................................................103System Level ................................................................................103

Summary and Conclusions ...........................................................................104References ........................................................................................................104Acknowledgments .........................................................................................104

Chapter 8 Advantages of a 48 Volt Belt Starter Generator in an Ultra-Light Vehicle Powertrain ......................................105

CULT - Cars Ultra-Light Technology ..........................................................106Hybrid Approach - 12 V BSG .......................................................................107

BSG (12 V) Hybrid Configuration .......................................................107Validation Process ..................................................................................108CO2 Saving Potentials and Comfort ....................................................109

Hybrid Approach - 48 V BSG .......................................................................112Introduction of 48 V Technology .........................................................112BSG (48 V) Hybrid Configuration .......................................................113Electric Driving Potential ......................................................................115Energy Management .............................................................................118CO2 Saving Potentials ............................................................................12148 V Plug-In Concept ............................................................................123

Summary .........................................................................................................123References ........................................................................................................124Acknowledgments .........................................................................................125About the Editor .............................................................................................127

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