Due to the discrepancy among series-connected cells in a lead-acid battery pack, the restored capacities may not be the same during the charging/discharging processes. Through repeated charging and discharging, one can find that the unbalance of individual series-connected battery cell of lead-acid battery is getting worse, because those cells of poor state of charge may have negative voltage, causing reverse charging from the other cells. This abnormal operation results in not only more energy consumption, but also the acceleration of the battery-cell aging and the remarkable reduction of its lifetime. For the purpose of investigating this problem, the operating characteristics of each cell is under study. The battery cells are purposely charged by different floating voltages and discharged by different cutoff voltages. The investigation results show that the lifecycles of battery cells are affected more significantly by floating charging voltage than by the discharging cutoff voltage. It is also found that a long time reverse charging has a destructive effect on the battery cells.

The aim of this master´s thesis is optimalization and methods of measuring the internal resistance of lead acid accumulator. First focus is on the analysis of properties of lead acid accumulators, their construction and negative effects. After that a method of measuring the internal resistance of experimental accumulator is processed. In this thesis practical design of measuring workplace is completed. The frequency analysis of impedance of charging and discharging accumulator is performed. After that the graph of internal resistance for various amplitude intensities, for various signal forms and also for various size of frequencies of alternating current are processed. The result of this thesis is a comparison of graphic works addictions charging and discharging characteristics of lead acid accumulator and determination of optimal amplitude, form and intensity of frequency of alternating current in point when internal resistance is evaluated correctly.

Energy systems in every part of the world are experiencing accelerated shifts towards more sustainable solutions which will bring far-reaching changes to our daily lives. These rapid transitions will bring impactful and vital changes to the way we fuel our cars, heat our homes and power our industries in the approaching decades. [1] The automotive sector is in high pace to electrify their cars. The number of electric passengercar sales is expected to increase by more than a factor of 60 between 2018 to 2050. Which means by that time there could be approximately 2 billion EVs on the roads and they all need batteries to run on. [1] ManyEuropean electric vehicle manufacturers have started marketing their future models globally, but automotiveli.-ion battery manufacturing capacity in Europe is merely 2.1% of the total global automotive li-ion batteryproduction. [2] Increase in sales of EV-s and energy storage systems drives the demand for li-ion batteries. This research is conducted in collaboration with Northvolt, one of the newcomers to the li-ion batterymanufacturing market in Europe. Northvolt is a Swedish-founded company in 2016, and despite its young age, Northvolt has prominent partners including BMW Group, Epiroc, Scania and the Volkswagen Group. Northvolt is with global ambition to produce the world's greenest battery cell with minimal possible carbon footprint in its Gigafactory in Sweden with 32GWh annual manufacturing capacity. Also, together with Volkswagen a 50/50 joint venture has been established to produce batteries in a 16GWh factory in Germany. After entering in different supplier agreements, Northvolt has sold a considerable amount of its first Gigafactory NV Ett production capacity to its key customers with a united equivalent of over $13billion until 2030. [3]Setting up lithium-ion battery factories for the automotive industry is a challenging task. It requires high speed and flexibility to keep up with the growing demand in a short time and still meeting all the stakeholder's requirements while keeping the highest environmental standards in place during production. To keep up with the growing demand and customer requirements a state-of.the-art industrialization project management strategy is developed. Therefore, state-of.the-art automotive project management, new product industrialization and development practices are investigated together with the best practices from the wider industry. Furthermore, Northvolt's current industrialization project management strategies are examined, and improvement proposals and tools are developed to ramp-up the current and future factories with shorter time, less cost and highest possible quality. The main aim of the thesis is to develop a project management solutions to lead industrialization of li-ionbattery Giga-factories successfully and help Northvolt fuel our cars, heat our homes, and power our industries more sustainably and innovatively. The expected outcome of the thesis is five tools developed that support the industrialization of LIB production facilities in Europe to increase the EU LIB manufacturing capacity. / Energisystem genomgår en snabb omväxling till allt mer hållbara lösningar, vilket kommer påverka våra liv markant. Dessa snabba omväxlingar kommer påverka samt främja sättet hur vi driver våra bilar, värmer våra hus och försörjer våra industrier, flera år framåt. [1] Bilsektorn som har skiftat sitt fokus till elektrifiering av sina bilar, där antalet sålda elbilar förväntas att öka sextifaldigt mellan 2018 och 2050. Detta kommer att leda till att cirka 2 miljarder elbilar kommer att åka på vägarna globalt och alla dessabilar kommer behöva framförallt litiumjonbatterier. [1] Majoriteten av biltillverkare i Europa har börjatutveckla framtida elektrifierade bilmodeller. Tillverkningen av litiumjonbatterier för elbilar i Europa utgörendast 2.1 % av den globala tillverkningen totalt. [2] En ökad försäljning av elbilar och även av produkterför energilagring, ökar efterfrågan på litiumjonbatterier. Den här undersökningen har tagits fram i samarbete med Northvolt som är en av nykomlingarna inomtillverkningen av litiumjonbatterier i Europa. Northvolt är ett svenskt bolag som startades 2016 och trotsdess tidiga fas, har de lyckats samverka med prominenta samarbetspartners som BMW group, Epiroc, Scania och Volkswagen group. Northvolts ambition är att skapa världens grönaste batteri med ett minimalt klimatavtryck. Denna produkt utvecklas i deras så kallade Gigafactory som ligger i Skellefteå och vars årliga produktion uppnår 32 Gwh. Utöver det har Northvolt i samarbete med Volkswagen fått i uppdrag att bygga upp en batterifabrik i Tyskland, vars tillverkningskapacitet kommer att uppnå till 16Gwh årligen. Efter att ha ingått i flera leverantörsavtal har Northvolt sålt en avsevärd mängd av sin produktionskapacitet för den planerade fabriken Gigafactory NV Ett till sina nyckelkunder. Detta motsvarar en investering på 13 miljarder dollar fram till 2030. [3]Att etablera en fabrik som tillverkar litiumjonbatterier för bilindustrin är en utmanande uppgift. Det kräversnabba beslut och flexibilitet för att hålla jämna steg med den växande efterfrågan på batterier av denna typ. Batterierna ska hålla måttet för de krav som kunderna har, och även ska de uppfylla alla internationella standarder för ett miljövänligt batteri.För att kunna upprätthålla den växande efterfrågan och kundkraven utvecklas nya metoder inom projektledning för att effektivisera produktionen. Det allra senaste praxis i projektledning, produktion och produkttillverkning inom bilindustrin analyseras. Dessutom beaktas senaste metoderna och praxis från andra industrier. Vidare kartläggs northvolts nuvarande strategi för deras hantering av produktionsfasen för att föreslå förbättringar och verktyg, som kan effektivisera uppbyggnaden och driften av framtida fabriker. Huvudsyftet med denna avhandling är att utveckla nya metoder inom projektledning för att kunnautveckla produktionsfasen för framtida fabriker som tillverkar litiumjonbatterier. Detta kommer leda tillatt Northvolt kommer vara en del av våra framtida liv genom att hjälpa oss att driva våra fordon, värma våra hem och driva våra fabriker på ett hållbart och effektivt sätt. Det förväntade resultatet i denna avhandling är fem utvecklade verktyg som stödjer utbyggnaden av Litiumjonbatteri fabriker i Europa föratt öka dess totala årliga produktion.

Due to climate change, the energy system needs to change from traditional fossil fuels to be dominated by renewable energy sources. Not only the energy system, but the increasing number of vehicles and emissions from the transport sector are a problem for climate change and that need to be solved. Both can be solved with batteries, to handle climate change issue. The lithium-ion batteries (LIBs) have a high energy density which is important due to the less needed materials for the batteries. LIBs can be used in a battery energy storage system (BESS) to store the excess energy for later usage, and as an electric vehicle (EV) battery. For these high energy density batteries, there comes drawbacks such as safety issues by deviating temperatures which have effects on the capacity, lifetime, performance, and in worst case a thermal runaway can occur which may lead to fire and explosions. These temperature issues can be solved with a battery thermal management system (BTMS), which can manage temperature deviation. Cylindrical battery cells with the dimension 18650 with the cell chemistry Lithium-Nickel-Cobalt-Aluminum-Oxide (NCA) will be investigated with different discharge rates, how the heat generation increases, and how it can be handled by cooling systems. A battery pack will be built up in computational fluid dynamics (CFD) software called Ansys Fluent, to be simulated and see how the influence of cooling methods affect the energy density of the 18650 batteries. Air-cooling and liquid-cooling with fan as air-cooling and plate cooling as liquid cooling will be used in this work. 20 cells were investigated with air and liquid cooling, with two different cases with air-cooling. 100 cells with just liquid cooling during 0,5C was investigated on how the number of cells impacted on the energy density. It was seen that the different discharge rates (C-rate) had an impact on the amount of cooling, with air cooling being not as good as liquid cooling for cooling the battery pack and more flow was needed. The energy density in relation to weight showed that 20 cells with less spacing using air-cooling had the best energy density at 196,68 Wh/kg. It was also seen that the number of cells had an impact on the energy density in relation to volume. With the best energy density with 100 cells using liquid cooling at 279,96 Wh/L.

Over the last ten years the Li-ion battery cells plays a significant role in the world’s decarbonization and reduction of CO2 emission. They are widely applied in many industries, such as consumer electronics, transportation and energy storage industries. The number of batteries cells varies from a few to thousands in a battery application, they are connected in series and/or parallel according to their designed voltage and capacity. It is a great advantage to be able to electrically connect the positive and negative sides of the battery from one side when designing and manufacturing battery modules and battery packs, because the whole built height of module could be a little lower and the rest of space below the cell body is free for cooling or thermal management. In this thesis project, different bonding technologies were compared, and ultrasonic wire bonding was selected to connect the negative electrode (shoulder) of battery and busbar. However, bonding on the shoulder of battery was still a challenge. The mechanism of ultrasonic wire bonding and the surface condition of the shoulder were studied in the project in order to develop the bonding process. Besides, the DoE experiment was used to further optimize the parameters of the wire bonding process. The 4 most influential factors were obtained from 7 factors from the screening factor experiment. Then a full factorial experiment was carried out for evaluation. Finally, a series of optimized parameters could be summarized. / Under de senaste tio åren har litiumjonbattericellerna spelat en betydande roll för världens koldioxidutsläpp och minskning av CO2-utsläpp. De används i stor utsträckning inom många industrier, såsom hemelektronik, transport och energilagringsindustrier. Antalet battericeller varierar från några få till tusentals i en batteriapplikation, de är seriekopplade och/eller parallellt beroende på den spänning och kapacitet de är avseddaför. Det är en stor fördel att kunna koppla ihop batteriets positiva och negativa sidorelektriskt på samma sida när man designar och tillverkar batterimoduler ochbatteripaket, eftersom hela bygghöjden på modulen kan vara lite lägre och resten av utrymmet under cellkroppen är fri för kylning eller termisk hantering. I detta examensarbete jämfördes olika bindningsteknologier och ultraljudstrådsbindning valdes för att ansluta den negativa elektroden (axeln) på batteriet och samlingsskenan. Att fästa på axeln av batteriet var dock fortfarande en utmaning. Mekanismen för ultraljudstrådbindning och axelns yttillstånd studerades i projektet för att utveckla bindningsprocessen. Dessutom användes DoE-experimentet för att ytterligare optimera parametrarna för trådbindningsprocessen. De 4 mest inflytelserika faktorerna erhölls från 7 faktorer från screeningfaktorexperimentet. Därefter utfördes ett fullständigt faktorexperiment för utvärdering. Slutligen kunde en serie optimerade parametrar sammanställas.

The demand for high energy battery assemblies is growing in sectors such as transportation. Alongwith it is the need for reliable, efficient and cost-effective ways to electrically connect the batteries toensure their performance. Battery cells are most often put into modules or packs when produced forelectrically driven vehicles. The variable of greatest influence when welding battery packs is thecontact resistance between the cell and the connection tab. It is crucial to minimize this variable asmuch as possible to prevent energy loss in the form of heat generation. The purpose of this project is to conduct a comparative literature study of different weldingtechniques for welding batteries. The compared techniques are resistance spot welding, laser beamwelding and ultrasonic welding. The performance was evaluated in terms of numerous factors such asproduction cost, degree of automation and weld quality. All three methods are tried and proven to function in the production of battery applications. Eachmethod has separate strengths and limitations which makes them complement each other. Thus, it isimportant to look at several factors when deciding which welding technique is the most suitable forthe desired application. The scale of production, economical aspects as well as battery cell geometrywere concluded to be the most important in making this decision.

This presented work deals with the development of an automated station for the measuring of experimental cells of the Lead Acid Battery. The principle is to design a measuring station and make programs for cycling of cells in standard and PSoC modes.

<p>Electrospinning has gained immense interests in recent years due to its potential application in various fields, including energy storage application. The V₂O₅/GO as a layered crystal structure has been demonstrated to fabricate nanofibers with diameters within a range of ~300nm through electrospinning technique. The porous, hollow, and interconnected nanostructures were produced by electrospinning formed by polymers such as Polyvinylpyrrolidone (PVP) and Polyvinyl alcohol (PVA), separately, as solvent polymers with electrospinning technique. </p> <p> </p> <p>In this study, we investigated the synthesis of a graphene-modified nanostructured V₂O₅ through modified sol-gel method and electrospinning of V₂O₅/GO hybrid. Electrochemical characterization was performed by utilizing Arbin Battery cycler, Field Emission Scanning Electron Microscopy (FESEM), X-ray powder diffraction (XRD), Thermogravimetric analysis (TGA), Mercury Porosimetery, and BET surface area measurement. </p> <p> </p> <p>As compared to the other conventional fabrication methods, our optimized sol-gel method, followed by the electrospinning of the cathode material achieved a high initial capacity of <b>342 mAh/g</b> at a high current density of 0.5C (171 mA/g) and the capacity retention of ~80% after 20 cycles. Also, the prepared sol-gel method outperforms the pure V₂O₅cathode material, by obtaining the capacity almost two times higher.</p> <p>The results of this study showed that post-synthesis treatment of cathode material plays a prominent role in electrochemical performance of the nanostructured vanadium oxides. By controlling the annealing and drying steps, and time, a small amount of pyrolysis carbon can be retained, which improves the conductivity of the V₂O₅ nanorods. Also, controlled post-synthesis helped us to prevent aggregation of electro-spun twisted nanostructured fibers which deteriorates the lithium diffusion process during charge/discharge of batteries.</p>

<p>A battery assembly experiences both mechanical and thermal loadings during its operation. It is critical to perform the thermomechanical analysis to propose a novel design for the highest efficiency.In this study,two main goals include mechanical characterization and deformation responses for a battery cell and assembly, as well as air-cooled concepts design and analysis.Initially, the cell dimensions were measured by cell-sectioning method, and then the mechanical properties were empirically measured by both 3-point flexural, and nanoindentation experiments. Moreover, three pairs of experiments and simulations were conducted to study mechanical behaviors on both a single cell and a battery assembly. They include (1) point-force loading for single, open cell; (2) internal pressurization for single, sealed cell; and (3) internal pressurization for battery assembly.Additionally, both parametric and experimental studies were executed to design, analyze,and validate air-cooled concepts based on the idea of microchannel heatsink. The proposed concepts have the features, which are integrated into the battery cell for generating the cooling channels. A series of thermomechanical simulations and a forced convection testbed were built for computationally and empirically analyzing the performances of the concepts. The results from the mechanical characterization showed a significant difference between the actual and nominal values of both cell dimensions and mechanical properties. Therefore, the effect of the manufacturing process to such values must be considered before inputting for analyzing the deformation responses. From the thermomechanical analyses, it was found that the mechanical loading might negatively influence the thermal performance if there were not enough mechanical supports from the air-cooling structure. The impact was minimal in the tapered-channel battery assembly. This configuration also significantly reduced the temperature difference on the cell compared with other concepts and the reference design.<br></p>

The (Battery management system)BMS has the task of ensuring that for the individual bat-tery cell parameters such as the allowed operating voltage window or the allowable temperature range are not violated. Since the battery itself is a highly distinct nonlinear electrochemical de-vice it is hard to detect its internal characteristics directly. The requirement of predicting battery packs’ present operating condition will become one of the most important task for the BMS. Therefore, special algorithms for battery monitoring are required.In this thesis, a model based battery state estimation technique using an adaptive filter tech-nology is investigated. Different battery models are studied in terms of complexity and accuracy. Following up with the introduction of different adaptive filter technology, the implementation of these methods into battery management system is decribed. Evaluations on different estimation methods are implemented from the point of view of the dynamic performance, the requirement on the computing power and the accuracy of the estimation. Real test drive data will be used as a reference to compare the result with the estimation value. Characteristics of different moni-toring methods and models are reported in this work. Finally, the trade-offs between different monitor’s performance and their computational complexity are analyzed. / BMS (eng. battery management system) har till uppgift att se till att viktiga parametrar såsom tillspännings- och temperaturintervall upprätthålls för varje individuell battericell. Då en battericells beteende är ickelinjärt är det svårt att bestämma cellens interna karakteristika direkt. Att kunna förutsäga dessa karakteristika för ett komplett batteripack kommer att en mycket viktig funktion hos framtida BMS. I detta examensarbete har en modellbaserad tillståndsestimeringsmetod med användande av adaptiv filtrering undersökts. Olika batterimodeller har studerats med avseende på komplexitet och noggrannhet. Efter introduktionen av olika metoder för adaptiv filtrering har dessa metoder implementerats i en BMS modell. Utvärdering av de olika metoderna för att åstadkomma tillståndsestimering har sedan utförts med avseende på dynamisk prestanda, krav på beräkningskraft och noggrannhet hos de resulterande estimaten. Data från uppmätta kördata från ett fordon har använts som referens för att jämföra de olika estimaten. Slutligen presenteras en jämförelse mellan de olika tillståndsestimeringsmetodernas prestanda när de appliceras på de olika batterimodellerna.