The fast-growing electric vehicles (EVs) market demands huge efforts from car manufacturers to develop and improve their current products’ systems. A fast charge of the battery pack is one of the challenges encountered due to the battery limitations regarding behaviour and additional degradation when exposed to such a rough situation. In addition, the outcome of a study performed on a battery does not apply to others, especially if their chemistries are different. Hence, extensive testing is required to understand the influence of design decisions on the particular energy storage device to be implemented. Due to batteries’ nonlinear behaviour that is highly dependent on external variables such as temperature, the dynamic load and aging, another defying task is the widely studied state of charge (SOC) estimation, commonly considered one of the most significant functions in a battery management system (BMS). This thesis presents an extensive battery fast charging aging test study equipped with promising current charging profiles from published literature to minimize aging. Four charging protocols are carefully designed to charge the cell from 10 to 80% SOC within fifteen minutes and have their performances discussed. A dual state estimation algorithm is modelled to estimate the SOC with the assistance of a capacity state of health (SOHcap) estimation. Finally, the dual state estimation model is validated with the fast charging aging test data. / Thesis / Master of Science in Mechanical Engineering (MSME)

The electric vehicle market has rapidly expanded due to technological advancements for the last decade and a key enabler is the development of high-performance batteries with greater energy density, faster charging, and longer lifespan. The construction equipment sector faces unique challenges in electrification, including high power demands, extended operating hours, and the need for minimal downtime. To address these challenges Volvo Construction Equipment is investigating a battery swap system solution that allows for quick battery swaps, reducing downtime and a decoupled lifetime from the machines. The aim for this study is to design a battery pack used for the battery swap system while answering the following research questions: RQ1: What configuration of battery modules, rack and auxiliary systems achieve the highest energy density when designing a battery pack for construction equipment? RQ2: What factors should be considered when designing the battery modules, rack, and auxiliary systems to achieve the highest energy density of a battery pack for construction equipment? This project followed a limited version of Ulrich et al.'s (2019) product development process, focusing on concept development and system-level design for a battery swapping system. An inductive research approach was taken, gathering qualitative and quantitative data from interviews, literature, documents, and meetings to create a holistic understanding of the project challenges. A structured literature review was conducted using relevant keywords across multiple databases, employing techniques like forward and backward snowballing. Data analysis methods, including conversation analysis, were employed to structure and analyze collected data, ensuring validity and reliability through triangulation, and cross-referencing with experts at Volvo. Empirical studies were conducted through benchmarking and a case study, providing quantitative data on specifications and qualitative insights from internal documentation and communication with product developers. The findings formed an iterative concept generation process, emphasizing the importance of exploring diverse possibilities in the early stages. The design process involved evaluating previous battery pack solutions, working within predefined constraints like using a specific shell, internally developed battery modules, auxiliary components while satisfying a set of stakeholder needs. Some auxiliary components and a rack that supports the battery modules were also developed as there is a new internal layout of the battery pack. This resulted in a conceptual battery pack that theoretically have a 30% higher energy density than the previous battery pack solutions. The proposed solution enables Volvo Construction Equipment to offer machines with longer runtimes and increased productivity by maximizing the energy storage capacity within the given constraints.

Lithium-ion based battery energy storage system has become one of the most popular forms of energy storage system for its high charge and discharge efficiency and high energy density. This dissertation proposes a high-efficiency grid-tie lithium-ion battery based energy storage system, which consists of a LiFePO4 battery based energy storage and associated battery management system (BMS), a high-efficiency bidirectional ac-dc converter and the central control unit which controls the operation mode and grid interface of the energy storage system. The BMS estimates the state of charge (SOC) and state of health (SOH) of each battery cell in the pack and applies active charge equalization to balance the charge of all the cells in the pack. The bidirectional ac-dc converter works as the interface between the battery pack and the ac grid, which needs to meet the requirements of bidirectional power flow capability and to ensure high power factor and low THD as well as to regulate the dc side power regulation. A highly efficient dual-buck converter based bidirectional ac-dc converter is proposed. The implemented converter efficiency peaks at 97.8% at 50-kHz switching frequency for both rectifier and inverter modes. To better utilize the dc bus voltage and eliminate the two dc bus bulk capacitors in the conventional dual-buck converter, a novel bidirectional ac-dc converter is proposed by replacing the capacitor leg of the dual-buck converter based single-phase bidirectional ac-dc converter with a half-bridge switch leg. Based on the single-phase bidirectional ac-dc converter topology, three novel three-phase bidirectional ac-dc converter topologies are proposed. In order to control the bidirectional power flow and at the same time stabilize the system in mode transition, an admittance compensator along with a quasi-proportional-resonant (QPR) controller is adopted to allow smooth startup and elimination of the steady-state error over the entire load range. The proposed QPR controller is designed and implemented with a digital controller. The entire system has been simulated in both PSIM and Simulink and verified with hardware experiments. Small transient currents are observed with the power transferred from rectifier mode to inverter mode at peak current point and also from inverter mode to rectifier mode at peak current point. The designed BMS monitors and reports all battery cells parameters in the pack and estimates the SOC of each battery cell by using the Coulomb counting plus an accurate open-circuit voltage model. The SOC information is then used to control the isolated bidirectional dc-dc converter based active cell balancing circuits to mitigate the mismatch among the series connected cells. Using the proposed SOC balancing technique, the entire battery storage system has demonstrated more capacity than the system without SOC balancing. / Ph. D.

Law / In this essay I consider whether or not there is a need for the creation of the crime of negligent assault. I start off by giving a brief exposition of the current position in South Africa with regard to assault. From this exposition it becomes clear that negligent assault is not recognised in South African law. I give a brief summary of the concepts of intention and negligence. After this I briefly discuss what criteria should be considered before invoking the criminal sanction. In the next section of the essay I consider the need for, and the benefits of, creating the crime of negligent assault. Lastly, I critically analyse whether the legislature should intervene or not. My conclusion is that the social benefits of criminalising the conduct do in fact outweigh the negative implications of not criminalising it, and that the legislature would not err if it were to create the crime of negligent assault. / LL.M.

Li-ion batteries are currently the most efficient technology available for electrochemical energy storage. The technology has revolutionized the portable electronics market and is becoming a corner stone for large scale applications, such as electric vehicles. It is therefore important to develop materials in which the energy storage relies on abundant redox active species, such as iron. In this thesis, new iron based electrode materials for positive electrodes in Li-ion batteries were investigated. Lithium iron pyrophosphate (Li2FeP2O7) and two polymorphs of lithium iron sulphate fluoride (LiFeSO4F) were studied. For Li2FeP2O7, preferred oxidation of iron with different coordination numbers within the crystal structure was studied, and six-coordinated iron was found to be oxidized preferentially at lower potentials compared to five‑coordinated iron. Electrochemical cycling resulted in structural changes of Li2FeP2O7 through an increased Li-Fe mixing in the compound, forming a metastable state during battery operation. For tavorite LiFeSO4F, the influence of the amount of a conductive polymer (poly(3,4-ethylenedioxythiophene), or PEDOT) was studied. All the different amounts of PEDOT coating reduced the polarization significantly, but the trade-off between functionality and weight added also has to be considered. Additionally, the effect of densifying the electrodes to different degrees is reported, and was found to have a significant influence on the battery performance. Also triplite LiFeSO4F was coated with PEODT, and it was found that the electrochemical performance improved, but not to the same extent as for tavorite LiFeSO4F. The faster solid state transport of Li-ions in tavorite type LiFeSO4F possibly accounts for the difference in electrochemical performance. Together, the results presented herein should be of importance for developing new iron based materials for Li-ion batteries. / Av de idag tillgängliga teknologierna för elektrokemisk energilagring så har litium-jonbatterier de bästa egenskaperna när det gäller energiförluster och energilagringskapacitet. De har revolutionerat marknaden för portabel elektronik (telefoner, laptops etc.), och blir mer och mer viktiga för storskaliga tillämpningar såsom elbilar. För den typen av applikationer måste teknologin baseras på vanligt förekommande material och grundämnen, t.ex. järn. I den här avhandlingen har järnbaserade material för den positiva elektroden hos litium-jonbatterier studerats. Olika aspekter som påverkar spänningen och effektiviteten hos elektroderna har undersökts. Ett exempel på det är hur olika omgivningar kring järnatomerna i en förening påverkar spänningen hos ett batteri. För föreningen litiumjärnpyrofosfat visade det sig att sex närmaste grannar ger lägre spänning än fem närmaste grannar till järn. Dessutom har förändringar i föreningens struktur studerats då den används i ett batteri. Den här typen av grundforskning är viktig för förståelsen av nya elektrodmaterial i Li-jonbatterier. Ur en mer praktisk synvinkel så har elektroder baserade på en annan järnförening, litiumjärnsulfatfluorid, utvecklats. Ledningsförmågan hos dessa elektroder har förbättrats genom att belägga föreningen med ett ledande skikt, samt att mekaniskt pressa samman elektroderna genom mangling. Båda metoderna är viktiga för att tillverka välfungerande elektroder. Föreningen litiumjärnsulfatfluorid förekommer i två olika former, och en jämförelse av hur elektriskt ledande beläggningar påverkar de bägge materialen har också gjorts i den här avhandlingen. Tillsammans visar resultaten från de olika studierna på hur man kan arbeta och tänka kring utvecklingen av nya material för litium-jonbatterier.

<p>The lithium ion battery is today mainly used in cell phonesand laptops. In the future, this kind of battery might beuseful in hybrid electric vehicles as well.</p><p>In this work, the main focus has been to gain more knowledgeabout the lithium ion battery in the hybrid electric vehicle(HEV) and more precisely to examine what processes of thebattery that are limiting at HEV currents. Both experiments andmathematical modelling have been used. In both cases, highrate, pulsed currents typical for the HEV, have been used.</p><p>Two manuscripts have been written. Both of them concern thebehaviour of the battery at HEV load, but from different pointsof view. The first one concerns the electrochemical behaviourof the battery at different ambient temperatures. Theexperimental results of this paper were used to validate amathematical model of a Li-ion battery. Possiblesimplifications of the model were identified. In this work itwas also concluded that the mass transfer of the electrolyte isthe main limiting process within the battery. The mass transferof the electrolyte was further studied in the second paper,where the concentration of lithium ions was measured indirectlyusing in situ Raman spectroscopy. This study showed that themathematical description of the mass transfer of theelectrolyte is not complete. One main reason of this issuggested to be the poor description of the physical parametersof the electrolyte. These ought to be further studied in orderto get a better fit between concentration gradients predictedby experiments and model respectively.</p>

This project represents a descriptive analysis of Forms I and II of the Luria-Nebraska Neuropsychological Battery and an investigation of the applicability of Item Response Theory in neuropsychological assessment. Test protocols of 1280 Form I examinees and 405 Form II examinees were analyzed by item and scale using Item Response Theory. The analysis consisted of investigation of the fit of LNNB data to the one and two-parameter IRT models, analysis of item and scale residuals and information values, comparison of traditional and IRT approaches in derivation of the Pathognomonic, Right Hemisphere and Left Hemisphere scales and comparison of two IRT approaches to the identification of biased items. In general, the one-parameter model did not fit the LNNB data. The two-parameter model, however provided a generally good fit to the data. Scale residuals and information functions indicate that the LNNB scales are unidimensional and accurately measure their underlying pyschological constructs. Item analysis identified several items on each scale that do not contribute to the measurement of the scalar trait. Suggestions were made for deletion, relocation or alteration of these items to improve their measurement properties. Substantial differences were found between Form I and Form II based on item characteristic curves and b-value differences. The nature of these differences suggested that the size and ability distribution of the Form II sample may have prevented accurate parameter estimation, obscuring the comparison of the two forms of the battery. A number of items on the Pathognomonic, right Hemisphere and Left Hemisphere scales were identified that contribute little to the measurement properties of these scales. Additional items not on these scales, were identified that are candidates for inclusion on these scales. Comparison of the statistical tests of b-value differences with ICC differences, for identification of potentially biased items, suggests that the latter method may be more efficacious in the neuropsychological domain. It is concluded that the LNNB is an accurate and content valid test of neuropsychological abilities; that IRT methods could improve the measurement properties of the scales and that ICC differences are an effective approach to item bias detection.

No description available.

This project examines the implications of the photovoltaic power generation as well as the battery storage systems on the distribution network tariff structures. Different types of existing distribution tariffs were applied to the residential households’ demand patterns. Several scenarios of demand profiles were theoretically investigated. First scenario included households’ consumption under current situation without on-site power production and any storage, second scenario concerned penetration of average size of solar panel installations and the last demand profile with maximum possible size of photovoltaic panels complemented with battery storage use. The distribution tariffs included in the comparison are: power based tariff and two energy based tariffs, one with flat-rate and another with time-of-use structure. Distribution tariffs were normalized with the aim to research the implications of the on-site production and storage use. Normalization factors were used when comparing financial bills from the households under above mentioned scenarios. Energy distribution tariffs have higher potential for households to save on their energy bill with the introduction of the on-site solar power utilization. On the other hand power tariff provides higher incentive for the implementation of the demand response strategies in the households.

The viability of any electric vehicle is critically dependent on it having an acceptable range between charges, a feature which is ultimately dictated by the capacity of the battery energy store. Considerable improvements in vehicle range are possible, however, by ensuring the most effective use of this limited energy resource through the minimisation of the losses in the electric drive-train, i.e. the combined machine and power electronic controller. A particular consideration is that, for the majority of the time, the electric drive-train will be operating at part load. The thesis investigates the operation of induction motor based electric traction drive-trains, with a view to minimising the system loss over typical driving cycles. The study is based around a 26kW induction motor and IGBT inverter drive, which is typical of the technology used to power a small urban vehicle. A potential advantage of an induction motor based drive-train is the ability to vary the level of excitation field in the motor, and therefore the balance of iron and copper loss. The control of the supply voltage magnitude necessitates the use of some form of modulation on the output of the power converter. The method of modulation employed will influence the harmonic content of the supply to the motor, the level of parasitic harmonic loss in the machine and the switching losses of the power semiconductors. A theoretical study supported by experimental work on a DSP controlled drive is presented and used to determine the most appropriate modulation strategy at a given operating point to achieve an optimal balance between the motor copper, iron and harmonic loss and inverter switching and conduction loss. It is shown that compared to the established method of constant flux and fixed inverter switching frequency control, a significant reduction in the traction system loss can be achieved. Some different modulation schemes involve varying amounts of computational overhead in a DSP, the implementation of candidate modulation and control schemes has also been investigated to ensure the defined scheme is practically realisable.