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World Electric Vehicle Journal is published by MDPI from Volume 9 issue 1 (2018). Previous articles were published by The World Electric Vehicle Association (WEVA) and its member the European Association for e-Mobility (AVERE), the Electric Drive Transportation Association (EDTA), and the Electric Vehicle Association of Asia Pacific (EVAAP). They are hosted by MDPI on mdpi.com as a courtesy and upon agreement with AVERE.

World Electr. Veh. J., Volume 6, Issue 3 (September 2013) – 38 articles , Pages 484-818

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Article
Towards advanced BMS algorithms development for (P)HEV and EV by use of a physics-based model of Li-ion battery systems
World Electr. Veh. J. 2013, 6(3), 807-818; https://doi.org/10.3390/wevj6030807 - 27 Sep 2013
Cited by 4 | Viewed by 612
Abstract
Onboard Hybrid Electric Vehicles (HEV) and Battery Electric Vehicles (BEV), the Battery Management System (BMS) is of critical importance to ensure safe and reliable use of the electrical energy stored inside Li-ion batteries until the End-Of-Life (EOL) of the electrochemical system. At any [...] Read more.
Onboard Hybrid Electric Vehicles (HEV) and Battery Electric Vehicles (BEV), the Battery Management System (BMS) is of critical importance to ensure safe and reliable use of the electrical energy stored inside Li-ion batteries until the End-Of-Life (EOL) of the electrochemical system. At any time, the BMS must indicate the allowable current limits for charge and discharge (CMI: Charge Maximal Intensity and DMI: Discharge Maximal Intensity) that the battery systems can safely absorb/supply at different temperatures (T) and states-of-charge (SOC) for a given pulse duration (tpulse) according to the electric power absorbed by the vehicle operational usage. CMI and DMI laws are generally specified by the battery manufacturer based on experimental tests campaigns. In this paper, BMS specifications laws are investigated for Li(NixCoyAlz)O2/Graphite (NCA/C) Li-ion technology through a physics-based battery model which allows the analysis of different physical phenomena that impact the system performance according to operating conditions. The CMI and DMI are then compared to the battery manufacturer data. Finally, the DMI and CMI are implemented in a Battery Intensity Management Algorithm (BIMA) which is validated at the simulation level. This practical method can be generalized to other Li-ion chemistries, enabling efficient model-based design of conventional BMS laws with regard to cell limits in terms of (over)potentials, current, temperature, and aging mechanisms. Full article
Article
Classical EIS and square pattern signals comparison based on a well-known reference impedance
World Electr. Veh. J. 2013, 6(3), 800-806; https://doi.org/10.3390/wevj6030800 - 27 Sep 2013
Cited by 3 | Viewed by 695
Abstract
Electrochemical impedance spectroscopy or ac impedance methods are popularly used for the diagnosis of electrochemical generators (batteries or fuel cell). It is now possible to acquire and quantitatively interpret the experimental electrical impedances of such systems, whose evolutions indirectly reflect the modifications of [...] Read more.
Electrochemical impedance spectroscopy or ac impedance methods are popularly used for the diagnosis of electrochemical generators (batteries or fuel cell). It is now possible to acquire and quantitatively interpret the experimental electrical impedances of such systems, whose evolutions indirectly reflect the modifications of the internal electrochemical process. The scope of these measurement methods is to identify the frequency response function of the system under test by applying a small signal perturbation to the system input, and measuring the corresponding response. Once identified, and according to the application, frequency response functions can provide useful information about the characteristics of the system. Classical EIS consists in applying a set of frequency-controlled sine waves to the input of the system. However, the most difficult problem is the integration of this type of measuring device in embedded systems. In order to overcome this problem, we propose to apply squared pattern excitation signals to perform such impedance measurements. In this paper, we quantify and compare the performance of classical EIS and the proposed broadband identification method applied to a well-known impedance circuit. Full article
Article
Using on-board Electrochemical Impedance Spectroscopy in Battery Management Systems
World Electr. Veh. J. 2013, 6(3), 793-799; https://doi.org/10.3390/wevj6030793 - 27 Sep 2013
Cited by 3 | Viewed by 521
Abstract
As the need for better prediction of battery life parameters in secondary batteries evolves, especially for electric vehicles, many researchers have looked for methods beyond simple battery modeling. One of the promising methods is electrochemical impedance spectroscopy. This is typically a technique used [...] Read more.
As the need for better prediction of battery life parameters in secondary batteries evolves, especially for electric vehicles, many researchers have looked for methods beyond simple battery modeling. One of the promising methods is electrochemical impedance spectroscopy. This is typically a technique used to get insight on the kinetic reactions in batteries and various studies have shown excellent correlation between impedance data and the state of health and ageing effects in lithium-ion batteries. In this article the benefits of using electrochemical impedance spectroscopy in battery management systems will be studied as it has been shown by multiple researchers that it is possible to develop an embedded electrochemical impedance spectroscopy circuit. The accuracy of currently available models based on impedance data deteriorates over time and to enable a battery management system to keep accurate predictions on state of health and other ageing-related effects there is a need for on-board electrochemical impedance measurements. Aspects such as SoH, balancing, battery ageing, and second life is discussed in relation to electrochemical impedance spectroscopy and battery management systems. Full article
Article
Fast Charging Method Based on Estimation of Ion Concentrations using a Reduced Order of Electrochemical Thermal Model for Lithium Ion Polymer Battery
World Electr. Veh. J. 2013, 6(3), 782-792; https://doi.org/10.3390/wevj6030782 - 27 Sep 2013
Cited by 7 | Viewed by 601
Abstract
Comparably long charging time for battery of electric and hybrid vehicles is one of barriers for massive commercialization of the vehicles. Typical charging methods are by a constant current (CC) with constant voltage (CV), pulsed or tapered current. Theoretically, the charging time can [...] Read more.
Comparably long charging time for battery of electric and hybrid vehicles is one of barriers for massive commercialization of the vehicles. Typical charging methods are by a constant current (CC) with constant voltage (CV), pulsed or tapered current. Theoretically, the charging time can be reduced by increased amplitude of the charging current, which, however, accelerate degradation of cells and reduces the lifespan. The relationship between the charging current and the degradation has not been well understood. Studies on ion transport and chemical reactions using a computational model developed in our laboratory reveal that a high charging current causes excessive ions at the surface of electrode particles because of slow diffusion process of ions in the solid electrodes. The excessive lithium ions react with electrons and form a thin layer, called Lithium plating that is irreversible. The Lithium plating not only reduces ion conductivities, but also contributes growth of dendrites and potentially internal short circuit. In this paper, a new charging algorithm is proposed that is based on an electrochemical and thermal model, which order is drastically reduced in order to facilitate a real time operation. The model, called Reduced Order of Electrochemical Thermal Model (ROM), is completely validated with a pouch type of Lithium polymer battery and used to dynamically estimate ion concentration at the surface of particles. Based on the estimated ion concentration, a new control algorithm is derived that allows for determination of amplitude and duration of the charging current. The ROM performs at least ten fold faster in calculations than the original full order model. The simulation and experimental results show that the charging time can be reduced to 60-70% of that of the classical CC/CV charging by preventing excessive ions and slowing down degradation of cell capacity losses. Full article
Article
Proposal and Validation of a SOC Estimation Algorithm of LiFePO4 Battery Packs for Traction Applications
World Electr. Veh. J. 2013, 6(3), 771-781; https://doi.org/10.3390/wevj6030771 - 27 Sep 2013
Cited by 3 | Viewed by 752
Abstract
An accurate onboard State-of-Charge (SOC) estimation is one of the key functions a Battery Management System (BMS) has to perform in order to provide the optimal performance management of the battery system under control. In this framework, this paper presents a proposal of [...] Read more.
An accurate onboard State-of-Charge (SOC) estimation is one of the key functions a Battery Management System (BMS) has to perform in order to provide the optimal performance management of the battery system under control. In this framework, this paper presents a proposal of an Enhanced Coulomb Counting (CC) State-of-Charge estimation algorithm based on Constant Voltage Charge Detection (CVCD) and Open Circuit Voltage (OCV) model for LiFePO4 batteries. Designed for onboard BMS implementation, it is characterized by its simplicity and operability in wide operating conditions (under diverse load profiles, temperatures, SOC ranges, etc.). The description of the algorithm at both, cell and battery-module level is detailed in the paper. Furthermore, its on-line experimental validation and scope determination is tested under three different traction applications and cell specimens in an own-developed real time validation platform: 2.5 Ah cells (Type A) in a residential elevator application, 8 Ah cells (Type B) in a pure electric on-road vehicle application and 100 Ah cells (Type C) in an electric railway vehicle application. According to the achieved results, the accuracy and versatility of the algorithm for different operating scenarios is certainly proven. In the worst case scenario the algorithm is capable of keeping the SOC estimation of the system under test stabilized around 5% of error. Full article
Article
Detection of Electric Arcs in Large Batteries
World Electr. Veh. J. 2013, 6(3), 762-770; https://doi.org/10.3390/wevj6030762 - 27 Sep 2013
Cited by 1 | Viewed by 643
Abstract
This paper addresses the precocious detection of electric arcs in an electric vehicle battery generated by a connector fault. The detection principle is based on the acoustic emission of the arc. First, the identification of the electric arc acoustic signature as well as [...] Read more.
This paper addresses the precocious detection of electric arcs in an electric vehicle battery generated by a connector fault. The detection principle is based on the acoustic emission of the arc. First, the identification of the electric arc acoustic signature as well as disturbances in the environment of detection has been realized. Subsequently, we have been focused on the propagation of acoustic waves emitted by the arc in the confined environment of the battery. We proposed a detection method based on correlation whose performance was evaluated. Finally, a localization system based on signal time-difference-of-arrival estimation and triangulation is described and assessed. A demonstrator has been developed and validates the detection performance. Full article
Article
Iterative capacity estimation of LiFePO4 cell over the lifecycle based on SoC estimation correction
World Electr. Veh. J. 2013, 6(3), 752-761; https://doi.org/10.3390/wevj6030752 - 27 Sep 2013
Cited by 3 | Viewed by 496
Abstract
Real time state of charge (SoC) and state of health (SoH) monitoring plays an essential role in electric vehicles, hybrid electric vehicles and generally in battery powered applications. Between these two state estimations, only the SoC has been studied rigorously until the current [...] Read more.
Real time state of charge (SoC) and state of health (SoH) monitoring plays an essential role in electric vehicles, hybrid electric vehicles and generally in battery powered applications. Between these two state estimations, only the SoC has been studied rigorously until the current dates, while SoH or capacity estimation are much less referenced on the literature. Additionally, the SoC and the SoH estimation are strongly correlated by widely used coulomb counting equation and consequently wrong capacity estimation would lead to a SoC estimation error, which in turn, will lead to a further capacity estimation error. In this sense, the first job was to develop the equivalent electric model, design SoC estimator and to verify both of them experimentally. Then, different alternative techniques for estimating the capacity are analyzed, selecting the best choice considering the observability degree of the object of estimation: capacity. Then, in this paper we propose a new method for estimating the capacity, called iterative transferred charge, which adapts the current capacity estimation value based on the SoC correction made by the corresponding estimator. Finally, the developed algorithm is evaluated by comparing the capacity estimation with the reference over the life of the cell, by extensive experimental tests. Full article
Article
CAE Based Noise Optimization of Switched Reluctance Electric Motors for Automotive Powertrains
World Electr. Veh. J. 2013, 6(3), 747-751; https://doi.org/10.3390/wevj6030747 - 27 Sep 2013
Cited by 1 | Viewed by 585
Abstract
This paper focuses on simulation of noise radiated by Switched Reluctance Motors for automotive powertrains. Since control for maximum efficiency leads to high torque ripple and noise radiation, optimizing the NVH behaviour is essential. The simulation approach, based on electro-magnetic and vibro-acoustic finite [...] Read more.
This paper focuses on simulation of noise radiated by Switched Reluctance Motors for automotive powertrains. Since control for maximum efficiency leads to high torque ripple and noise radiation, optimizing the NVH behaviour is essential. The simulation approach, based on electro-magnetic and vibro-acoustic finite element models and applicable to other electric motors, is illustrated with concrete results. Full article
Article
Effect of punching and stress concentrations on mechanical behaviour of electrical steels
World Electr. Veh. J. 2013, 6(3), 741-746; https://doi.org/10.3390/wevj6030741 - 27 Sep 2013
Cited by 1 | Viewed by 532
Abstract
ArcelorMittal supplies advanced mechanical and magnetic material data for its iCAReTM line of electrical steels to enable customers to optimise the design of their e-machines . This paper gives an overview of the experimental methodologies to assess the effect of stress concentrations [...] Read more.
ArcelorMittal supplies advanced mechanical and magnetic material data for its iCAReTM line of electrical steels to enable customers to optimise the design of their e-machines . This paper gives an overview of the experimental methodologies to assess the effect of stress concentrations and punched edges on the fatigue behaviour of thin gauge electrical steel sheets. The link between the mechanical properties and the microstructural and metallurgical features of the different materials is discussed. Full article
Article
safe Torque Vectoring function for an electric vehicle
World Electr. Veh. J. 2013, 6(3), 731-740; https://doi.org/10.3390/wevj6030731 - 27 Sep 2013
Cited by 1 | Viewed by 655
Abstract
A safe Torque Vectoring function is applied to an electric vehicle with a two front motors drivetrain concept. The function has been embedded in a lean and scalable functional architecture adaptable to various drivetrain concepts. The Torque Vectoring function comprises an LPV control [...] Read more.
A safe Torque Vectoring function is applied to an electric vehicle with a two front motors drivetrain concept. The function has been embedded in a lean and scalable functional architecture adaptable to various drivetrain concepts. The Torque Vectoring function comprises an LPV control algorithm with good performance even in extreme test cases. The controller can be parameterised for case specific performance. The implementation of functional safety requirements is presented for one safety goal. Full article
Article
Electric and Hybrid Vehicle Power Electronics Efficiency, Testing and Reliability
World Electr. Veh. J. 2013, 6(3), 719-730; https://doi.org/10.3390/wevj6030719 - 27 Sep 2013
Cited by 4 | Viewed by 807
Abstract
System efficiency together with the reliability are the most critical factors in the design, characterization and operation of Electric and Hybrid Vehicles. This paper summarizes those aspects from the system level down to the component details and shows practical methods for evaluation and [...] Read more.
System efficiency together with the reliability are the most critical factors in the design, characterization and operation of Electric and Hybrid Vehicles. This paper summarizes those aspects from the system level down to the component details and shows practical methods for evaluation and improvement. This paper concentrates on a small to medium size personal vehicles in electric vehicle (EV) and parallel hybrid (HEV) configuration. Even though the main focus of the paper is the traction inverter, other critical high power EV and HEV building blocks such as a DC/DC and AC/DC on board charger are also characterized and discussed to certain depth. Some test methods for evaluation of the individual units and their components including extreme conditions such as heavy overload, short circuit and overvoltage are explored along with examples of experimental results on the prototype units. Full article
Article
Different Novel Electric Machine Designs for Automotive Applications
World Electr. Veh. J. 2013, 6(3), 712-718; https://doi.org/10.3390/wevj6030712 - 27 Sep 2013
Cited by 5 | Viewed by 634
Abstract
This paper presents three-different high efficiency and low costs electric machines types for automotive applications. For the PM machines with the single-layer concentrated windings, a novel stator topology with magnetic flux barriers in the stator teeth is used to increase the power density [...] Read more.
This paper presents three-different high efficiency and low costs electric machines types for automotive applications. For the PM machines with the single-layer concentrated windings, a novel stator topology with magnetic flux barriers in the stator teeth is used to increase the power density and the efficiency of the machine. Using this technique the material amount for the considered PM machine is reduced about 20% compared with the conventional design. For the asynchronous machines, two alternative solutions are presented; a new winding type with low space harmonic contents and also an ASM rotor with series connection of rotor bars solve the problem with high harmonics. Further, during the design of a new self-excited synchronous machine with concentrated winding, the high MMF winding harmonics are used to excite the rotor field winding. Full article
Article
How simulation can help defining necessary speed sensor-bearing performance for asynchronous motor control
World Electr. Veh. J. 2013, 6(3), 707-711; https://doi.org/10.3390/wevj6030707 - 27 Sep 2013
Cited by 1 | Viewed by 461
Abstract
This paper presents a method to define the optimum sensor performance to meet customer requirements on asynchronous motor performance parameters such as efficiency or output torque ripple. The method uses simulation: a speed sensor-bearing simulation tool is coupled with an asynchronous motor model [...] Read more.
This paper presents a method to define the optimum sensor performance to meet customer requirements on asynchronous motor performance parameters such as efficiency or output torque ripple. The method uses simulation: a speed sensor-bearing simulation tool is coupled with an asynchronous motor model of the electromechanical parts as well as the motor control to perform a reduced Design of Experiments study using the extreme outcomes for the sensor as inputs to the motor system model. Subsequently, a mapping of the efficiency or another output parameter of the motor can be realized with respect to the torque and speed range selected. This mapping is checked against the desired minimum performance required by the customer, to finalize the assessment of the sensor-bearing performance with a robustness verification. The method has been applied to a case where two different variants of sensor populations have been tested in a certain given motor and control configuration. The results show that it is possible to predict the necessary sensor-bearing performance in terms of motor performance. Full article
Article
The Value of a Clutch Mechanism in Electric Vehicles
World Electr. Veh. J. 2013, 6(3), 696-706; https://doi.org/10.3390/wevj6030696 - 27 Sep 2013
Cited by 1 | Viewed by 677
Abstract
This paper examines the benefits of a drivetrain that is able to disengage its propulsion motor from the driveline in an electric vehicle. The drivetrain was developed for an ultra-efficient eco vehicle competing in the Shell 2013 Eco Marathon. Various clutch mechanisms were [...] Read more.
This paper examines the benefits of a drivetrain that is able to disengage its propulsion motor from the driveline in an electric vehicle. The drivetrain was developed for an ultra-efficient eco vehicle competing in the Shell 2013 Eco Marathon. Various clutch mechanisms were examined. In spite of the complexity and losses associated with additional bearings and release surfaces, an actuated dog clutch was chosen as it offers superior performance due to the dual capability of freewheeling and regenerative braking that results. Track data from the event is presented along with experimental work that indicates that the clutch mechanism reduces power consumption by more than 35% for a ferrous permanent magnet propulsion motor. Savings were reduced to 5% for a coreless permanent magnet motor coupled to the driveline via an 11:1 straight cut spur gear arrangement. This reduced saving was due to the removal of hysteresis and eddy current losses from the stator. The paper also demonstrates during a competition in which the driver was aware of the energy consumption, the driving style changed when the technological option to free wheel was available. Finally the study was inferred onto a real world application with further experimental and simulation work on the Delta E4 Coupe, a high performance electric sports car. The vehicle uses a ferrous permanent magnet direct drive arrangement, indicated a reduction in power consumption of 10 to 14%. It is hoped that these insights are relevant when considering the development of electric vehicle drivetrains where machine topology and drive cycle will determine the value of a clutch mechanism. Full article
Article
Mechanically actuated variable flux IPMSM for EV and HEV applications
World Electr. Veh. J. 2013, 6(3), 684-695; https://doi.org/10.3390/wevj6030684 - 27 Sep 2013
Cited by 13 | Viewed by 553
Abstract
The current trend in production EVs/HEVs is to use interior permanent magnet synchronous motors (IPMSM) as the means of providing power to the vehicle drive train. The efficiency of these machines can be extremely high (>95%) although this typically occurs in a relatively [...] Read more.
The current trend in production EVs/HEVs is to use interior permanent magnet synchronous motors (IPMSM) as the means of providing power to the vehicle drive train. The efficiency of these machines can be extremely high (>95%) although this typically occurs in a relatively narrow range in the middle of the machine speed-torque curve. This is a concern for automotive applications as vehicles operate across the full range of speeds and torques; typical urban drive cycles operate in the low speed/torque region where efficiencies can drop to below 80%. Clearly there is a mismatch between the region of high efficiency of the machine and the region of highest operation duty of EVs/HEVs. This paper presents a method of expanding the peak efficiency region of the machine by introducing a method for adjusting the permanent magnet flux linkage utilising a mechanism that short circuits the flux at the end caps of the rotor using solid steel plates. These plates are operated such that they can switch between open and closed positions depending on the demand on the machine allowing the flux linkage to be varied. Analysis shows that by applying the plates to short the flux in the rotor the flux linkage in low torque/high speed applications is lowered whilst reducing the need for high flux weakening currents in the d-axis. This reduces current consumption, improving the power factor and therefore increases the overall efficiency of the machine. The performance of the system is verified using a proof of concept IPMSM. Full article
Article
An Approach to an Optimal Design of Permanent Magnet Synchronous Machines for Battery Electric Vehicles
World Electr. Veh. J. 2013, 6(3), 673-683; https://doi.org/10.3390/wevj6030673 - 27 Sep 2013
Cited by 2 | Viewed by 674
Abstract
The described design of a permanent magnet synchronous motor for battery electric vehicles is based on a drive cycle. For a given vehicle a set of operating points of the electric machine can be derived from the cycle. The next step in the [...] Read more.
The described design of a permanent magnet synchronous motor for battery electric vehicles is based on a drive cycle. For a given vehicle a set of operating points of the electric machine can be derived from the cycle. The next step in the design of the traction motor is to find a suitable lamination layout. Common motor design procedures take only a few representative operating points into account. This paper describes an approach which includes a large number of operating points at early stages of the motor design process. It is based on a specialized motor model and an optimization strategy which are described in this paper. As an example a traction motor for the VW Golf CityStromer is designed by using the proposed method. Full article
Article
Air-Cooled Full-SiC High Power Density Inverter Unit
World Electr. Veh. J. 2013, 6(3), 669-672; https://doi.org/10.3390/wevj6030669 - 27 Sep 2013
Cited by 2 | Viewed by 525
Abstract
A 70 kVA/L air-cooled full-SiC three-phase inverter unit including power semiconductor modules, power capacitors, bus bars, gate drive circuits, a PWM wave generator and blower fans has been fabricated as a prototype for EV-use. SiC JFETs and SBDs of 1200 V were used. [...] Read more.
A 70 kVA/L air-cooled full-SiC three-phase inverter unit including power semiconductor modules, power capacitors, bus bars, gate drive circuits, a PWM wave generator and blower fans has been fabricated as a prototype for EV-use. SiC JFETs and SBDs of 1200 V were used. It has generated three-phase alternative power of 25 kVA to drive a 15 kW-class induction motor with only 190 W of dissipation. The module's temperature was at most 90 ºC. Full article
Article
Fuel Displacement Potential of a Thermoelectric Generator in a Conventional Vehicle
World Electr. Veh. J. 2013, 6(3), 663-668; https://doi.org/10.3390/wevj6030663 - 27 Sep 2013
Cited by 2 | Viewed by 454
Abstract
This paper evaluates the fuel displacement potential of a Thermoelectric Generator (TEG) device in a conventional gasoline vehicle using vehicle simulation and engine in the loop. A TEG device was modelled in Simulink, to exhibit the thermal and electrical characteristics of such a [...] Read more.
This paper evaluates the fuel displacement potential of a Thermoelectric Generator (TEG) device in a conventional gasoline vehicle using vehicle simulation and engine in the loop. A TEG device was modelled in Simulink, to exhibit the thermal and electrical characteristics of such a device. This TEG model was integrated into the vehicle simulation software, Autonomie and evaluated in a real engine – virtual vehicle scenario using Engine in the loop (EIL) technique. The EIL approach was used to evaluate the fuel consumption benefit of TEG under cold and hot conditions. The complete vehicle model was then validated and used to evaluate the impact of the current TEG system on additional drive cycles as well as future TEG systems (i.e. no device temperature limits). EIL evaluation shows a fuel economy gain within the current device of 1% on the US06 cycle. The simulation study will quantify the impact of driving cycles and TEG design on fuel displacement potential. Full article
Article
High power LiFePO4 cell evaluation: Fast charge, Depth of Discharge and Fast discharge dependency
World Electr. Veh. J. 2013, 6(3), 653-662; https://doi.org/10.3390/wevj6030653 - 27 Sep 2013
Cited by 3 | Viewed by 630
Abstract
High power lithium iron phosphate (LFP) batteries suitable for Electric Vehicles are tested in this work. An extended cycle-life testing is carried out, consisting in various types of experiments: standard cycling, optimized fast charge with high constant current discharge (4 C) and simulating [...] Read more.
High power lithium iron phosphate (LFP) batteries suitable for Electric Vehicles are tested in this work. An extended cycle-life testing is carried out, consisting in various types of experiments: standard cycling, optimized fast charge with high constant current discharge (4 C) and simulating driving dynamic stress protocols (DST). The fast charge/DST discharge tests are carried out with depth of discharge (DOD) dependency (100% DOD and partial 50% DOD discharge). A complete analysis of the cycling results is developed, showing an overall good performance of the tested batteries. In all of experiments, long term U.S. Advanced Battery Consortium goals are met: fast charging, cycle life and specific energy. Only the long term specific energy goal is not achieved, which is a drawback intrinsic in this technology. The results provide useful information for battery selection, BMS designs and other applications in EV industry. Full article
Article
Modelling of Li-ion Batteries Dynamics using Impedance Spectroscopy and Pulse Fitting: EVs Application
World Electr. Veh. J. 2013, 6(3), 644-652; https://doi.org/10.3390/wevj6030644 - 27 Sep 2013
Cited by 1 | Viewed by 560
Abstract
One of the most relevant tasks that must be carried out by a Battery Management System (BMS) is the diagnosis of the battery state. An important part of the algorithms used for determining the State of Charge (SOC) or the State of Health [...] Read more.
One of the most relevant tasks that must be carried out by a Battery Management System (BMS) is the diagnosis of the battery state. An important part of the algorithms used for determining the State of Charge (SOC) or the State of Health (SOH) requires a cell model to run. The most precise is the model used, the best is the estimation achieved by the algorithm. In this paper, two techniques for obtaining a model of the cell dynamics and calculating its parameters are analyzed: the time domain characterization and the frequency domain or impedance-based characterization. Their principal characteristics and some relevant considerations to take into account are explained, as well as the obtained results. The performance of both models is compared in terms of the voltage error and the requirements to use them. Finally, a combined methodology is proposed to overcome the problems which can appear when each technique is employed. The resultant model is validated at 25 ºC in all SOC range using real measurements of a 40 Ah Li-ion cell with different current profiles, including pulses of diverse lengths and FUDS driving cycles. The tests show small error between the real response of the cell and the output of the model. Full article
Article
Application of the Thermal Impedance Spectroscopy method in three dimensions to a large prismatic Li-ion cell
World Electr. Veh. J. 2013, 6(3), 638-643; https://doi.org/10.3390/wevj6030638 - 27 Sep 2013
Viewed by 476
Abstract
Thermal impedance spectroscopy (TIS) is applied for the thermal characterization of a large prismatic battery cell. The method is based on previously published work and is extended to a three dimensional system. By using a discretized three dimensional model, the experimental results can [...] Read more.
Thermal impedance spectroscopy (TIS) is applied for the thermal characterization of a large prismatic battery cell. The method is based on previously published work and is extended to a three dimensional system. By using a discretized three dimensional model, the experimental results can be fitted to obtain the specific heat capacity and heat conductivity of the cell in three dimensions. The results show good agreement with the available data in the literature. Suggestions are made to improve the test setup to gain more confidence in the results and to increase the precision of the model. Full article
Article
Development of 2D Thermal Battery Model for Lithium-ion Pouch Cells
World Electr. Veh. J. 2013, 6(3), 629-637; https://doi.org/10.3390/wevj6030629 - 27 Sep 2013
Cited by 16 | Viewed by 794
Abstract
This paper represents a simulation model for a 2D-thermal model applied on a Lithium-ion pouch battery. This model is able to describe the transient response of the thermal distribution accurately. The heat generation parameters used in this model have been obtained experimentally from [...] Read more.
This paper represents a simulation model for a 2D-thermal model applied on a Lithium-ion pouch battery. This model is able to describe the transient response of the thermal distribution accurately. The heat generation parameters used in this model have been obtained experimentally from dedicated estimation technique. The experimental and simulation are performed at different charge and discharge current rates. The experimental results are in good agreement with the developed model. The battery thermal distributions using natural and forced convection cooling are studied. Full article
Article
Energy Management Strategy Based on Frequency-Varying Filter for the Battery Supercapacitor Hybrid System of Electric Vehicles
World Electr. Veh. J. 2013, 6(3), 623-628; https://doi.org/10.3390/wevj6030623 - 27 Sep 2013
Cited by 4 | Viewed by 583
Abstract
Hybrid Energy Storage System (HESS), which combines the battery and supercapacitor (SC), is a potential solution for the energy system of Electric Vehicles (EV). In this paper, a battery and SC hybrid system for small-scale EV with Energy Management Strategy (EMS) and power [...] Read more.
Hybrid Energy Storage System (HESS), which combines the battery and supercapacitor (SC), is a potential solution for the energy system of Electric Vehicles (EV). In this paper, a battery and SC hybrid system for small-scale EV with Energy Management Strategy (EMS) and power interface design is introduced. The energy management and power sharing strategy based on frequency-varying filter method is proposed, aiming to realize both high energy density output and high power density output from HESS. The design and control aspects of the converter as the interface of SC bank are introduced. The experiment results in reduced scale test validate that the energy management strategy is effective and the converter control satisfies the requirement of HESS in our hybrid EV prototype. Full article
Article
Research on Simplification of Simulating the Heat Conduction in the Lithium-ion Battery Core
World Electr. Veh. J. 2013, 6(3), 611-622; https://doi.org/10.3390/wevj6030611 - 27 Sep 2013
Cited by 1 | Viewed by 579
Abstract
This paper discusses the model simplifing issue in battery thermal simulation. The paper verifies that for the large power battery simplifying the multilayer battery core as a lumped cuboid is reasonable. So when doing simulation, building a multilayer core is unnecessary. And the [...] Read more.
This paper discusses the model simplifing issue in battery thermal simulation. The paper verifies that for the large power battery simplifying the multilayer battery core as a lumped cuboid is reasonable. So when doing simulation, building a multilayer core is unnecessary. And the calculation cost can be reduced by the lumped model. Specific power battetry of 70Ah is dissembled to be modeld. Thermal models of are established, including models with a lumped core and with multilayer cores. For the lumped core, the anisotropic thermal conductivities are got by equations calculating series and parallel equivalent thermal conductivity. While for the multilayer core models, the core contains numbers of unit cells and the volume of which is equal to that of the lumped. In addition, under the boundary conditions of inner heat source and surface heating, steady state simulations are performed. Simulation results indicate that the temperature distributions of the lumped model and the multilayer model are almost the same. For one thing, large number of multilayers and low shell thermal conductivity contribute to a uniform temperature distribution within the core, so it is reasonable to simplify the multilayer core as a lumped cuboid. For another, due to the size of the battery and the shell property, it is difficult to find a simple curve to fit the simulation temperature on the battery surface. Although minor differences still exist, the lumped core can well subsitute the multilayer core in battery thermal simulation. Full article
Article
Lithium-ion Battery Electro-thermal Model and Its Application in the Numerical Simulation of Short Circuit Experiment
World Electr. Veh. J. 2013, 6(3), 603-610; https://doi.org/10.3390/wevj6030603 - 27 Sep 2013
Cited by 3 | Viewed by 629
Abstract
As a key issue in EVs (Electric Vehicles) development, Li-ion battery’s thermal safety is focused on in which the thermal abuse model is an important tool. This paper has established a 3-D electro-thermal model taking side reaction into account, in order to study [...] Read more.
As a key issue in EVs (Electric Vehicles) development, Li-ion battery’s thermal safety is focused on in which the thermal abuse model is an important tool. This paper has established a 3-D electro-thermal model taking side reaction into account, in order to study on MGL100Ah lithium manganite battery’s safety issue. This paper firstly states the mechanism of heat generation, types of thermal model, and the mesh model, then analyzes the simulation on the model under the short circuit condition, one of thermal abuse condition. On one hand, the paper verifies the liability of the model, so as to apply the model on other thermal abuse condition in the future; on the other hand, the paper discusses in detail the internal temperature distribution, voltage and current changes under the short circuit condition. Analyzing this typical safety issue in details, this paper can help reduce cost, raise design efficiency and avoid thermal abuse in future development of battery. Full article
Article
Energy Storage Systems for Electric Vehicles: Performance Comparison based on a Simple Equivalent Circuit and Experimental Tests
World Electr. Veh. J. 2013, 6(3), 592-602; https://doi.org/10.3390/wevj6030592 - 27 Sep 2013
Viewed by 494
Abstract
The decision to select the most suitable type of energy storage system for an electric vehicle is always difficult, since many conditionings must be taken into account. Sometimes, this study can be made by means of complex mathematical models which represent the behavior [...] Read more.
The decision to select the most suitable type of energy storage system for an electric vehicle is always difficult, since many conditionings must be taken into account. Sometimes, this study can be made by means of complex mathematical models which represent the behavior of a battery, ultracapacitor or some other devices. However, these models are usually too dependent on parameters that are not easily available, which usually results in nonrealistic results. Besides, the more accurate the model, the more specific it needs to be, which becomes an issue when comparing systems of different nature. This paper proposes a practical methodology to compare different energy storage technologies. This is done by means of a linear approach of an equivalent circuit based on laboratory tests. Via these tests, the internal resistance and the self-discharge rate are evaluated, making it possible to compare different energy storage systems regardless their technology. Rather simple testing equipment is sufficient to give a comparative idea of the differences between each system, concerning issues such as efficiency, heating and self-discharge, when operating under a certain scenario. The proposed methodology is applied to four energy storage systems of different nature for the sake of illustration. Full article
Article
Thermal Impedance Spectroscopy for Li-Ion Batteries with an IR Temperature Sensor System
World Electr. Veh. J. 2013, 6(3), 581-591; https://doi.org/10.3390/wevj6030581 - 27 Sep 2013
Cited by 5 | Viewed by 722
Abstract
Thermal impedance spectroscopy (TIS) is a non-destructive method for characterizing thermal properties of entire battery cells. Heat capacity, thermal conductivity and heat exchange with environment are deter-mined by an evaluation of the heat transfer behavior of the battery. TIS measurements are usually conduct-ed [...] Read more.
Thermal impedance spectroscopy (TIS) is a non-destructive method for characterizing thermal properties of entire battery cells. Heat capacity, thermal conductivity and heat exchange with environment are deter-mined by an evaluation of the heat transfer behavior of the battery. TIS measurements are usually conduct-ed with contact-based temperature sensors, such as thermocouples or thermistors, which show drawbacks at higher convection rates and higher temperature differences between battery and environment. To elude drawbacks in these kinds of sensors, an infrared-based temperature sensor system for battery sur-face temperature measurements is implemented. TIS measurements are conducted with this sensor system and with conventional, contact-based temperature sensors. Accuracy and reliability of thermal parameter identification is analyzed for the different sensor systems. Moreover, thermal parameters are identified for different cylindrical 18650 Li-ion cells with capacities between 1.1 Ah and 2.7 Ah. The comparison of different types of temperature sensors shows that contact-based sensors underestimate surface temperatures even at low temperature differences to environment. This causes an error in thermal parameter identification. The TIS measurements performed with contact-based sensors show divergence of 20 - 60 % for heat capacity, 30 - 70 % for thermal conductivity and 20 - 60 % for convective heat exchange with environment. With our IR temperature sensor system, parameter identification is performed for different batteries. Re-sulting values for specific heat capacity are in a range between 900 and 1020 J/kgK and thermal conduc-tivities in radial direction lies between 3.1 and 3.6 W/mK. Our investigations show that IR-based temperature sensors are an effective progression for TIS measure-ments and improve quality of parameter identification at low cost. Moreover, discrepancies mentioned in TIS literature can be explained by our findings. Full article
Article
Electrical safety of commercial Li-ion cells based on NMC and NCA technology compared to LFP technology
World Electr. Veh. J. 2013, 6(3), 572-580; https://doi.org/10.3390/wevj6030572 - 27 Sep 2013
Cited by 15 | Viewed by 2682
Abstract
Since a laptop caught fire in 2006 at the latest, Li-ion cells were considered as more dangerous than other accumulators [1]. Recent incidents, such as the one involving a BYD e6 electric taxi [2] or the Boeing Dreamliner [3], give rise to questions [...] Read more.
Since a laptop caught fire in 2006 at the latest, Li-ion cells were considered as more dangerous than other accumulators [1]. Recent incidents, such as the one involving a BYD e6 electric taxi [2] or the Boeing Dreamliner [3], give rise to questions concerning the safety of L#i-ion cells. This is a crucial point, since Li-ion cells are increasingly integrated in all kinds of (electric) vehicles. Therefore the economic success of hybrid electric vehicles (HEV) and battery electric vehicles (BEV) depends significantly on the safety of Li-ion cells. Lithium nickel manganese cobalt oxide (NMC) and lithium nickel cobalt aluminium oxide (NCA) are two standard Li-ion cathode chemistries, which are often used for today’s HEVs and BEVs Li-ion batteries. Cells with this two cathode technologies are investigated in detail and compared to cells with the alleged save lithium iron phosphate (LFP) technology. Furthermore only commercially available and mass produced Li-ion cells were tested, in order to get as close to real end-user applications as possible. To ensure comparability, cells with the most common 18650 casing have been used. Furthermore all cells had no built-in resistor with positive temperature coefficient (PTC-device). For each abuse test at least 2 cells have been tested to get to know the statistical dispersion. The spread was in all tests for all measured values of each cell type lower than 11 %. Consequently it can be supposed, that mass produced cells show equal behaviour also in abusive test. The performed electrical safety tests on these cells, involve overcharge, overdischarge and short circuit tests. These tests represent real abuse scenarios and are geared to established standards [15], [16], [17], [18]. To complete these measurements an accelerated rate calorimetry (ARC) test has been carried out, to determine the thermal stability of the cells. As in the literature discussed, the investigated LFP/C cells show a higher thermal stability and are therefore safer, although they do not have any overcharge buffer as the investigated NCA/C and NMC/C cells. Full article
Article
Development and realization of lithium-ion battery modules for starting applications and traction of off-road electric vehicles
World Electr. Veh. J. 2013, 6(3), 562-571; https://doi.org/10.3390/wevj6030562 - 27 Sep 2013
Cited by 1 | Viewed by 595
Abstract
The paper describes the development and realization of standard battery modules 12 V, made by LiFePO4 cells selected in a previous study by ENEA and the University of Pisa. Module means the group of four cells series connected, the electronic battery management [...] Read more.
The paper describes the development and realization of standard battery modules 12 V, made by LiFePO4 cells selected in a previous study by ENEA and the University of Pisa. Module means the group of four cells series connected, the electronic battery management system, the thermal management system and the mechanical case. Standard means that the same battery module can be used for different applications: in fact, the previous study showed that three standard battery modules, 30 Ah (little size), 60 Ah (medium size) and 100 Ah (large size), are sufficient to reach the levels of voltage/capacity requested by the most part of the applications in the field of the starting/auxiliary supply batteries (also for the nautical sector) and traction of off-road electric vehicles. More units of standard modules can be series/parallel connected to build complete battery systems able to satisfy the required performances. The development and realization of the modules mostly consisted of testing the selected cells to verify their suitability for the above mentioned applications, to make a thermal battery characterization so to define the thermal management system, to develop an electronic battery management system and to build a mechanical case. The paper shows all these aspects in detail. Full article
Article
Analysis of Degradation Mechanism of Lithium Iron Phosphate Battery
World Electr. Veh. J. 2013, 6(3), 555-561; https://doi.org/10.3390/wevj6030555 - 27 Sep 2013
Cited by 3 | Viewed by 664
Abstract
The degradation mechanisms of lithium iron phosphate battery have been analyzed with 150 day calendar capacity loss tests and 3,000 cycle capacity loss tests to identify the operation method to maximize the battery life for electric vehicles. Both test results indicated that capacity [...] Read more.
The degradation mechanisms of lithium iron phosphate battery have been analyzed with 150 day calendar capacity loss tests and 3,000 cycle capacity loss tests to identify the operation method to maximize the battery life for electric vehicles. Both test results indicated that capacity loss increased under higher temperature and SOC conditions. And also, large increase of internal resistance on the high temperature and high SOC conditions was confirmed by AC impedance tests. The real cycle capacity loss characteristic was derived by subtracting the capacity decrease due to calendar capacity loss during the cycle test from the overall capacity loss characteristic obtained from the cycle test. As a result, it is found that the real capacity loss contains not only structural disorders of electrode but also degradation factors due to the chemical reactions. Characteristics of degradation were quantified with equations based on the chemical kinetics. With this degradation prediction, an operation method was proposed that is compatible with the long life of batteries and the safety driving of a vehicle. As a result, with optimizing the SOC range used in the operation as follows: 30-10% in the warm seasons, 45-25% in the cold seasons, it was found that batteries can last 4 times longer than it used with high SOC range in every season. Full article
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