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In this study, Fuel Cell Vehicles (FCVs) are implemented to reduce the negative impacts caused by electric vehicle parking lots connected to the electricity grid. The main objective of the current study is to propose a dual-function control method for grid integration of vehicular fuel cells located in FCVs to reduce the harmonic pollution emitted to the grid by other electric vehicles and connected charging stations. The proposed control method is tested on a single-stage grid connection and is provided directly via inverter without using an additional converter, in contrast to the traditional two-stage structure. A dual-function single-stage vehicular fuel cell system is designed and operated to verify the reduction of harmonic distortion problems caused by grid-connected electric vehicles in the charging process. With the proposed structure, in addition to harmonic elimination, the system contributes to the reduction of energy consumption by supplying power to the grid/electric vehicles. In the system, the vehicular fuel cell, which feeds electric vehicle parking lots ranging from 4 kW to 12.1 kW, is designed to have a maximum power of 24.57 kW. Distortion values varying between 5.76 % and 23.01 % are reduced up to 0.45 % and 1.52 % with the ability to eliminate the harmonics. • Design of single-stage vehicular PEM fuel cell connected to the grid. • Dual functional control capability including energy management and harmonic reduction. • Effects of electric vehicle parking lots in charging process. • Elimination of additional dc-dc converter interface in single-stage system. [ABSTRACT FROM AUTHOR]

Extending lithium-ion battery lifetime is essential for mainstream uptake of electric vehicles. However, battery degradation is complex and involves coupling of underpinning electrochemical, thermal and mechanical processes, with behaviours varying based on chemistry, operating conditions and design. Derating is an attractive approach for extending lifetime due to ease of implementation, however, uncertainties remain around the optimal approach and their impacts. In this paper, we present a critical review of derating methods; dividing approaches into dynamic or static approaches based on whether the derated parameters changed with battery aging or not. Furthermore, we analyse and comment on approaches which are classified as being either heuristic or model-based. Analysis, comparison, and discussion around the derating sub-categories are presented towards highlighting underpinning insights of derating. Benefits and impacts of derating are quantified, and challenges with implementation are identified along with identification of research gaps, practical considerations and perspectives for future directions. [Display omitted] • Derating methods for extending battery lifetime reviewed, classified and compared. • Highlight underpinning insights of derating by analysing complex aging mechanisms. • Quantify benefits and impacts of experimentally validated derating approaches. • Discuss the industry implementation of derating methods and its challenges. • Identify research gaps and deliver perspectives toward advanced derating methods. [ABSTRACT FROM AUTHOR]

Subzero-temperature charging for lithium-ion batteries is an unsolved challenge due to dramatically low charging speed and capacity and a high risk of lithium deposition. Here, we propose a multi-objective optimization framework for the heated-charging, where the battery is rapidly warmed up to enhance its performance followed by fast charging. The echelon-current charging approach is developed with the boundary of maximum acceptable charging current at different states, which facilitates fast charging while preventing lithium deposition. Three critical and competing objectives, the heated-charging time and energy consumption, and charging capacity, are formulated, enabling the framework capable of comprehensively assessing the heated-charging method. We systematically discuss the influence of witching temperature from heating to charging on three charging objectives. With the optimization algorithm, an optimal switching temperature is determined to achieve not only fast charging with a high charging capacity but also low energy consumption. Experimental and simulation results validate that the proposed optimal charging method can charge the battery to 95% state-of-charge in 27 min at −30 °C while circumventing lithium plating. The charging comparison confirms that the proposed method boosts the charging speed by 26 times, which provides an opportunity to develop a fast charging method in extremely cold conditions. [Display omitted] • A multi-objective optimization framework for the heated-charging method at <0 °C • Optimal switching temperature from heating to charging determined for −30 °C charging • Heated-charging is fully discussed and quantitatively assessed with three metrics • Experimentally validate the Li plating-free fast charging with low energy loss • The charging comparison demonstrates the rapidity of the proposed method [ABSTRACT FROM AUTHOR]

Extreme temperatures pose several limitations to electric vehicle (EV) performance and charging. To investigate these effects, we combine a hybrid artificial neural network-empirical Li-ion battery model with a lumped capacitance EV thermal model to study how temperature will affect the performance of an EV fleet. We find that at −10 °C, the self-weighted mean battery charging power (SWMCP) decreases by 15% compared to standard 20 °C temperature. Active battery thermal management (BTM) during parking can improve SWMCP for individual vehicles, especially if vehicles are charged both at home and at workplace; the median SWMCP is increased by over 30%. Efficiency (km/kWh) of the vehicle fleet is maximized when ambient temperature is close to 20 °C. At low (−10 °C) and high (+40 °C) ambient temperatures, cabin preconditioning and BTM during parking can improve the median efficiency by 8% and 9%, respectively. At −10 °C, preconditioning and BTM during parking can also improve the fleet SOC by 3–6%-units, but this also introduces a “base” load of around 140 W per vehicle. Finally, we observe that the utility of the fleet can be increased by 5%-units by adding 3.6 kW chargers to workplaces, but further improved charging infrastructure would bring little additional benefit. [ABSTRACT FROM AUTHOR]

Concerns have been expressed regarding the displacement of harmful emissions from internal combustion engine vehicle (ICEV) tailpipes to the sources of electricity generation used to charge electric vehicles (EV). The degree to which EVs can reduce the environmental impacts of road transportation is dependent on the fuel mix of electricity generation within a country and on the real-time charging behaviours of EV users since the fuel mix of electricity generation frequently changes. This paper analyses the varying environmental impacts of EVs based on contrasting user behaviours and compares them to the environmental impacts of ICEVs. Individual EV user profiles are developed which comprise real data emerging from charge events undertaken in Ireland, and information is gathered on the actual CO 2 intensity of the electrical grid in real-time, allowing for the carbon intensity of every individual charge event to be determined using time and date information. The results show that the environmental impacts of EVs are highly influenced by the charging behaviours of individual users, and night-time charging was found to produce the largest environmental impact. EVs are shown to be a more environmentally friendly choice of vehicle than ICEVs under a wide majority of scenarios. [ABSTRACT FROM AUTHOR]

Development of microbial fuel cell (MFC) technology must address the challenges associated with energy extraction from large-scale MFC systems consisting of multiple modules. Herein, energy extraction is investigated with a 200-L MFC system (effective volume of 100 L for this study) treating actual municipal wastewater. A commercially available energy harvesting device (BQ 25504) is used successfully to convert 0.8–2.4 V from the MFCs to 5 V for charging ultracapacitors and running a DC motor. Four different types of serial connection containing different numbers of MFC modules are examined for energy extraction and conversion efficiency. The connection containing three rows of the MFCs has exhibited the best performance with the highest power output of ∼114 mW and the conversion efficiency of ∼80%. The weak performance of one-row MFCs negatively affects the overall performance of the connected MFCs in terms of both energy production and conversion. Those results indicate that an MFC system with balanced performance among individual modules will be critical to energy extraction. Future work will focus on application of the extracted energy to support MFC operation. [ABSTRACT FROM AUTHOR]

Abstract: The cranking and charging processes of a VRLA battery during stop–start cycling in micro-hybrid applications were simulated by one dimensional mathematical modeling, to study the formation and distribution of lead sulfate across the cell and analyze the resulting effect on battery aging. The battery focused on in this study represents a conventional VRLA battery without any carbon additives in the electrodes or carbon-based electrodes. The modeling results were validated against experimental data and used to analyze the “sulfation” of negative electrodes – the common failure mode of lead acid batteries under high-rate partial state of charge (HRPSoC) cycling. The analyses were based on two aging mechanisms proposed in previous studies and the predictions showed consistency with the previous teardown observations that the sulfate formed at the negative interface is more difficult to be converted back than anywhere else in the electrodes. The impact of cranking pulses during stop–start cycling on current density and the corresponding sulfate layer production was estimated. The effects of some critical design parameters on sulfate formation, distribution and aging over cycling were investigated, which provided guidelines for developing models and designing of VRLA batteries in micro-hybrid applications. [Copyright &y& Elsevier]

Fast charge of Li-ion cells is one of the main challenges in automotive battery application. As a particular problem at low temperatures and high charging rates, lithium deposits as metal on the anode surface (so-called lithium plating) instead of intercalation. Electrochemical models help to understand internal processes and predict aging effects, which finally lead to optimized charging strategies. In this work, a 1D + 1D (pseudo-2D) electrochemical model is developed, applied over a wide range of temperature (T = −25 °C to 40 °C) and current (I = 0.1 C to 6 C), and coupled with a 0D thermal model. The model is parameterized with measurement data in frequency domain using electrochemical impedance spectroscopy (EIS) and validated with time-domain data. In experiments cells are charged under different operating conditions. Capacity fade is measured after a significant number of cycles and compared to the simulated anode potential. A qualitative correlation is found between the degradation in experiment and the anode potential dropping below 0 V vs. Li/Li+ at the separator-anode boundary in the simulation. Furthermore a semi-quantitative expression for degradation is introduced. The transformation of the model into an on-board applicable form is presented in the companion contribution (part II). [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with occurrence of lithium plating on the negative electrode of lithium-ion batteries, a significant ageing phenomenon known to damage lithium-ion battery performances. Charge transfer process, one of the two different steps of the process of Li insertion in the negative active material being the cause of this ageing, was considered here to be the limiting process. This transfer occurs at short-time scales. The second process, the diffusion of lithium in the solid insertion compound, occurring at relatively long-time scales, has not been fully examined here. The aim of this paper was to develop a new method to evaluate the maximal rate of a charge pulse solicitation to prevent this ageing phenomenon. The approach relies on the use of a fundamental model of lithium ion battery with coupled mass and charge transfer. To validate the method, 2 s microcycles have been performed on a commercial VL41M SAFT cell. Theoretical and experimental works led to the maximum current density to be applied without undesired Li deposition, depending on the state of charge (SOC). The abacus established for the cell of interest can orient further specifications for suitable use of the battery. [Copyright &y& Elsevier]

Abstract: In this study, the sorting of nickel–metal hydride batteries is investigated based on their charging thermal behavior. A self-organization map (SOM) model affiliated to artificial neural network is constructed to conduct the sorting work. The sorting principle is described in detail to support the model. A batch of batteries is charged in various rates to collect training data closely related to battery thermal behavior. It is indicated that the model can master the regulation of sorting well after training. As a result, the batteries are classified by the SOM model into three categories of high heat generation battery, middle heat generation battery, and low heat generation battery, which corresponds well with the training result. The model thus allows the batteries in the same category to be selected for the consistency in thermal behavior as well as discharge performance. [Copyright &y& Elsevier]

Abstract: A simple circuit model is developed to describe supercapacitor behavior, which uses two resistor–capacitor branches with different time constants to characterize the charging and redistribution processes, and a variable leakage resistance to characterize the self-discharge process. The parameter values of a supercapacitor can be determined by a charging-redistribution experiment and a self-discharge experiment. The modeling and characterization procedures are illustrated using a 22F supercapacitor. The accuracy of the model is compared with that of other models often used in power electronics applications. The results show that the proposed model has better accuracy in characterizing the self-discharge process while maintaining similar performance as other models during charging and redistribution processes. Additionally, the proposed model is evaluated in a simplified energy storage system for self-powered wireless sensors. The model performance is compared with that of a commonly used energy recursive equation (ERE) model. The results demonstrate that the proposed model can predict the evolution profile of voltage across the supercapacitor more accurately than the ERE model, and therefore provides a better alternative for supporting research on storage system design and power management for wireless sensor networks. [Copyright &y& Elsevier]

Abstract: Electric vehicles are commonly seen as one of the alternatives to reduce the oil dependency and the greenhouse gas emissions in the transport sector. The aim of this paper is to evaluate the impact of different electric vehicle charging strategies on the national grid including the storage utilization of electric vehicles (V2G-vehicle to grid). Furthermore, an economic analysis of electric vehicle utilization is performed and the results are compared with the conventional diesel vehicle. To accomplish this aim the availability of passenger cars in Germany to be plugged into the grid showed to be high at any time over the day (>89%), which is advantageous for the V2G concept. The impact of the different electric vehicle charging strategies is investigated by employing three scenarios. The first scenario (unmanaged charging) shows that 1 mil. electric vehicles only impacts slightly on the daily peak electricity demand. In the second scenario (Grid stabilizing storage use) a maximum reductions of grid fluctuations of 16% can be achieved with the use of 1 mil. electric vehicles as storage. The last scenario (profit maximization by power trading) the maximum daily revenues from V2G activities are calculated to be 0.68 EUR2009. [ABSTRACT FROM AUTHOR]

Abstract: The main battery type employed in standby applications is the valve-regulated lead-acid (VRLA) battery. Float charging is normally used to maintain the battery in its fully charged state, however, float charging has limitations that can damage the battery and shorten its life. New charge regimes have evolved in recent years to tackle the intrinsic problems of float charging. The intermittent charge (IC) regime and the interrupted charge control (ICC) regime have been developed to prolong the service life of the battery in standby applications. The battery is normally maintained in the standby mode for a long period of time and there are infrequent discharge tests to verify the efficacy of the battery. Hence, the service life of the battery is highly correlated to its charge regime. This paper reviews the charge regimes for VRLA batteries, and assesses their charging performance and their impact on the service life of the battery. Recognising that temperature plays a significant role in battery operation, temperature compensation schemes are described for different charge regimes. [Copyright &y& Elsevier]

Abstract: Dynamic charge acceptance and charge acceptance under constant voltage charging conditions are for two reasons essential for lead-acid battery operation: energy efficiency in applications with limited charging time (e.g. PV systems or regenerative braking in vehicles) and avoidance of accelerated ageing due to sulphation. Laboratory tests often use charge regimes which are beneficial for the battery life, but which differ significantly from the operating conditions in the field. Lead-acid batteries in applications with limited charging time and partial-state-of-charge operation are rarely fully charged due to their limited charge acceptance. Therefore, they suffer from sulphation and early capacity loss. However, when appropriate charging strategies are applied most of the lost capacity and thus performance for the user may be recovered. The paper presents several aspects of charging regimes and charge acceptance. Theoretical and experimental investigations show that temperature is the most critical parameter. Full charging within short times can be achieved only at elevated temperatures. A strong dependency of the charge acceptance during charging pulses on the pre-treatment of the battery can be observed, which is not yet fully understood. But these effects have a significant impact on the fuel efficiency of micro-hybrid electric vehicles. [Copyright &y& Elsevier]

Abstract: The effect of the charging protocol on the cycle life of a commercial 18650 Li-ion cell was studied using three methods: (1) constant current (CC) charging, (2) constant power (CP) charging, and (3) multistage constant current (MCC) charging. The MCC-charging consists of two CC steps, which starts with a low current to charge the initial 10% capacity followed by a high current charging until the cell voltage reaches 4.2V. Using these methods, respectively, the cell was charged to 4.2V followed by a constant voltage (CV) charging until the current declined to 0.05C. Results showed that the cycle life of the cell strongly depended on the charging protocol even if the same charging rate was used. Among these three methods, the CC-method was found to be more suitable for slow charging (0.5C) while the CP-method was better for fast charging (1C). Impedance analyses indicated that the capacity loss during cycling was mainly attributed to the increase of charge-transfer resistance as a result of the progressive growth of surface layers on the surface of two electrodes. Fast charging resulted in an accelerated capacity fading due to the loss of Li+ ions and the related growth of a surface layer, which was associated with metallic lithium plating onto the anode and a high polarization at the electrolyte–electrode interface. Analyses of the cell electrochemistry showed that use of a reduced current to charge the initial 10% capacity and near the end of charge, respectively, was favorable for long cycle life. [Copyright &y& Elsevier]

Abstract: A three-electrode Li-ion cell with metallic lithium as the reference electrode was designed to study the charging process of Li-ion cells. The cell was connected to three independent testing channels, of which two channels shared the same lithium reference to measure the potentials of anode and cathode, respectively. A graphite/LiCoO2 cell with a C/A ratio, i.e., the reversible capacity ratio of the cathode to anode, of 0.985 was assembled and cycled using a normal constant-current/constant-voltage (CC/CV) charging procedure, during which the potentials of the anode and cathode were recorded. The results showed that lithium plating occurred under most of the charging conditions, especially at high currents and at low temperatures. Even in the region of CC charging, the potential of the graphite might drop below 0V versus Li+/Li. As a result, lithium plating and re-intercalating of the plated lithium into the graphite coexist, which resulted in a low charging capacity. When the current exceeded a certain level (0.4C in the present case), increasing the current could not shorten the charging time significantly, instead it aggravated lithium plating and prolonged the CV charging time. In addition, we found that lowering the battery temperature significantly aggravated lithium plating. At −20°C, for example, the CC charging became impossible and lithium plating accompanied the entire charging process. For an improved charging performance, an optimized C/A ratio of 0.85–0.90 is proposed for the graphite/LiCoO2 Li-ion cell. A high C/A ratio results in lithium plating onto the anode, while a low ratio results in overcharge of the cathode. [Copyright &y& Elsevier]

An overview of the design and development of a valve-regulated lead–acid (VRLA) battery with thin tubular plates is presented. Substantially improved specific energy in driving-cycle tests shows how the strategy of increasing the number of plate couples through the production of plates with component thicknesses that are 50% of those for existing technology plates is effective in meeting the requirements of the target application. Exploring the possibilities for removing inactive materials shows how reducing spine material to an extent limited to maintenance of an acceptable metal/active-material surface ratio (‘gamma’ value) by using an elliptical spine is effective, but that further reductions impair cell performance on cycling. Matching recharge characteristics with cell design and controlled initial electrolyte of the cells is discussed in terms of the influence of the oxygen-recombination rate on the recharge response. Changes during stable operation are illustrated in terms of charge response data during long cycle-life with 80% depth-of-discharge and a low, overcharge, viz., 4% C5. With an appropriate alloy, thin spines remain intact after more than 1000 cycles of service. Growth and non-penetrating corrosion rates are low for the optimized operating conditions. [Copyright &y& Elsevier]

The market for valve-regulated lead−acid (VRLA) batteries is growing steadily and will be given a further boost as the market for 36-V batteries for the 42-V PowerNet develops over the next few years. The manufacture of VRLA batteries poses, however, a number of complex technical problems that are not experienced in the manufacture of conventional flooded batteries. For the large-scale manufacture of automotive batteries or other small VRLA batteries of 100 Ah or less, jar formation rather than plate formation and dry charge would seem to be a logical and economically sound decision. For this to be successful, however, a number of key issues need to be reviewed, starting with a detailed consideration of battery design. This paper reviews issues associated with the jar formation of VRLA batteries. Guidance is given concerning filling techniques (gravity or vacuum fill), the formation process, charging techniques, and formation algorithms. Battery design and separator optimisation is discussed. The properties of the separator, e.g. wicking rate, fibre composition, surface area and compression, may have a critical impact on acid filling and jar formation, and may partially determine the filling and formation conditions to be used. The control of temperature during formation is particularly important. Formation algorithms and temperature data are presented. Attention is drawn to the possible loss of plate-group compression during the formation process, and how this may be avoided. [Copyright &y& Elsevier]

An expert panel replies to questions on lead-acid technology and performance asked by delegates to the Ninth Asian Battery Conference. The subjects are as follows. Grid alloys: effects of calcium and tin levels on microstructure, corrosion, mechanical and electrochemical properties; effect of alloy-fabrication process on mechanical strength and corrosion resistance; low dross-make during casting of lead–calcium–tin alloys; future of book-mould casting; effect of increasing levels of silver; stability of continuously processed grids at high temperature. Negative-plate expanders: function of lignosulfonates and barium sulfate; benefits of pre-blended expanders; optimum expander formulations. Valve-regulated batteries: effect of oxygen cycle; optimum methods for float charging; charging and deep-cycle lifetimes; reliability testing. [Copyright &y& Elsevier]

Lithium-ion batteries are considered fully charged when they are charged to the battery manufacturer's specified cut-off voltage using the specified cut-off C-rate. To assess the consequences of going beyond this charged state, four types of 18650 lithium-ion battery cells were charged from 100% state of charge until the cells' internal safety mechanisms were triggered, or thermal runaway occurred. The electrical, thermal, and mechanical behavior of the cells was monitored and compared using X-ray computed tomography, visual inspection, cross-sectional analysis, and scanning electron microscopy/energy dispersive X-ray spectroscopy analysis. In some samples, a unique degradation mechanism — electrode layer fracturing is identified, which is shown and discussed. Image 1 • Charged 4 types of 18650 cells from 100% state of charge until CIDs were triggered. • Analyzed the electrical, thermal and mechanical behavior during and post charge. • Identified a unique degradation mechanism during charge — electrode layer fracturing. • Analyzed the initiation of the electrode layer fracturing phenomenon. [ABSTRACT FROM AUTHOR]