List of abbreviations xi
List of symbols xiii
1. Introduction 1
1.1 Battery Management Systems 1
1.2 State-of-Charge definition 3
1.3 Goal and motivation of the research described in this book 4
1.4 Scope of this book 6
1.5 References 7
2. State-of-the-Art of battery State-of-Charge determination 11
2.1 Introduction 11
2.2 Battery technology and applications 11
2.2.1 General operational mechanism of batteries 13
2.2.2 Battery types and characteristics 14
2.2.3 Summary 16
2.3 History of State-of-Charge indication 16
2.4 A general State-of-Charge system 23
2.5 Possible State-of-Charge indication methods 24
2.5.1 Direct measurement 26
2.5.2 Book–keeping systems 32
2.5.3 Adaptive systems 34
2.5.4 Summary 37
2.6 Commercial State-of-Charge indication systems 38
2.7 Conclusions 41
2.8 References 42
3. A State-of-Charge indication algorithm 47
3.1 An introduction to the algorithm 47
3.2 Battery measurements and modelling for the State-of-Charge
indication algorithm 47
3.2.1 EMF measurement and modelling 48
3.2.2 Overpotential measurement and modelling 50
3.3 States of the State-of-Charge algorithm 52
3.4 Main issues of the algorithm 54
3.4.1 EMF measurement, modelling and implementation 55
3.4.2 Overpotential measurement, modelling and implementation 57
3.4.3 Adaptive systems 58
3.5 General remarks on the accuracy of SoC indication systems 59
3.6 Conclusions 59
3.7 References 60
4. Methods for measuring and modelling a battery’s
Electro-Motive Force 63
4.1 EMF measurement 63
4.2 Voltage prediction 69
4.2.1 Equilibrium detection 69
4.2.2 Existing voltage-relaxation models used
for voltage prediction 70
4.2.3 A new voltage-relaxation model 73
4.2.4 Implementation aspects of the voltage-relaxation model 75
4.2.5 Comparison of results obtained with the different
voltage-relaxation models 81
4.2.6 Summary 82
4.3 Hysteresis 83
4.4 Electro-Motive Force modelling 86
4.5 Conclusions 93
4.6 References 93
5. Methods for measuring and modelling a battery’s
overpotential 95
5.1 Overpotential measurements 95
5.1.1 Overpotential measurements involving partial
charge/discharge steps 95
5.1.2 Overpotential measurements involving full (dis)charge steps 100
5.2 Overpotential modelling and simulation 103
5.2.1 Overpotential modelling 103
5.2.2 Simulation results 104
5.3 Conclusions 108
5.4 References 109
6. Battery aging process 111
6.1 General aspects of battery aging 111
6.1.1 Li-ion battery aging 111
6.1.2 Qmax measurements 113
6.2 EMF measurements as a function of battery aging 114
6.2.1 The voltage-relaxation model as a function of
battery aging 114
6.2.2 EMF GITT measurement results obtained for
aged batteries 120
6.2.3 The charge/discharge Electro-Motive Force
difference as a function of battery aging 125
6.2.4 EMF modelling as a function of battery aging 130
6.3 Overpotential dependence on battery aging 132
6.3.1 Overpotential measurements as a function of aging 132
6.4 Adaptive systems 137
6.4.1 Electro-Motive Force adaptive system 137
6.4.2 Overpotential adaptive system 140
6.5 Conclusions 141
6.6 References 142
7. Measurement results obtained with new SoC algorithms
using fresh batteries 145
7.1 Introduction 145
7.2 Implementation aspects of the algorithm 146
7.2.1 A new SoC algorithm 146
7.2.2 Implementation aspects of the SoC algorithm 150
7.3 Results obtained with the algorithm using
fresh batteries 151
7.4 Uncertainty analysis 155
7.4.1 Uncertainty in the real-time SoC evaluation system 155
7.4.2 The SoC uncertainty 158
7.4.3 The remaining run-time uncertainty 161
7.5 Improvements in the new SoC algorithm 164
7.5.1 A new State-of-Charge-Electro-Motive Force
relationship 164
7.5.2 A new State-of-Charge-left model 165
7.5.3 Determination of the parameters of the new models 166
7.5.4 Test results 169
7.5.5 Uncertainty analysis 173
7.6 Comparison with Texas Instruments’ bq26500
SoC indication IC 174
7.6.1 The bq26500 SoC indicator 174
7.6.2 Comparison of the two SoC indicators 176
7.7 Conclusions 178
7.8 References 179
8. Universal State-of-Charge indication for
battery-powered applications 181
8.1 Introduction 181
8.2 Implementation aspects of the overpotential
adaptive system 182
8.3 SoC=f(EMF) and SoCl adaptive system 183
8.4 Results obtained with the adaptive SoC system
using aged batteries 185
8.5 Uncertainty analysis 188
8.6 Results obtained with other Li-based battery 189
8.6.1 EMF and SoCl modelling results obtained
for the Li-based battery 190
8.6.2 Experimental results 196
8.7 Practical implementation aspects of the SoC
algorithm 200
8.7.1 Hardware design of the evaluation board 200
8.7.2 Software design of the evaluation board 204
8.7.3 Measurement results 205
8.7.4 Boostcharging 208
8.8 Conclusions 218
8.9 References 219
9. General conclusions 221