Battery pack imbalance is one of the most pressing issues for companies involved in Battery Energy Storage. The importance of Battery Balancing with respect to Xtreme Power has been analysed in detail. Various methods of Battery Balancing have been researched and presented. Methods that were the most suitable to Xtreme Power's battery pack topology were selected and tested. The results of these experiments are presented and relevant conclusions are shown. / text

With increasing research on lithium batteries, the technology of electric vehicles equipped with lithium battery packs as the main energy storage system has become more and more mature, and the design and testing of lithium ion battery packs are becoming extremely important. As the battery system becomes more complex, it is necessary to optimize its structural design and to monitor its dynamic performance accurately. This research considers two related topics. The first is the design of a battery submodule made up of cylindrical lithium cells. The objective of this design is to improve its energy density and optimize the heat dissipation performance according to the installation position and space constraints in Ford Focus EV 2013, and, produce a submodule prototype based on this design; The second objective is to derive and verify an equivalent circuit model for a prismatic lithium battery cell of high energy capacity based on experimental results. In terms of mechanical structure, the basic structure of a battery pack is determined by the desired performance as well as cell characteristics. In this research, the Samsung 35E 18650 cylindrical cells are chosen. 20 battery cells are connected in parallel to form a battery submodule, and 13 battery submodules are connected in series to form a battery pack. The battery pack design process mainly includes positioning and connection of battery cells, heat dissipation mechanism, cabling and inside the pack. The above considerations were applied to prototype battery submodule with an energy density of 216.87 Wh/kg. Some key considerations in the design of the battery pack include checking the conductivity and the welding connection. Chemistry of lithium-ion batteries are constantly evolving with industrial demands which call for higher energy storage capacity. Therefore, this research selected a new high-capacity prismatic cell to establish an equivalent circuit model using characterization and experiments, followed by verification. A 280 Ah Lithium Iron Phosphate (LFP) prismatic battery cell was selected and characterized by testing under various operating conditions for validation, the Urban Dynamometer Driving Schedule (UDDS) was used. / Thesis / Master of Applied Science (MASc) / This thesis introduces how to design a battery pack using cylindrical battery cells, also shows how to conduct characterization tests and build a equivalent circuit battery model.

Electrification is essential to decarbonise the transport sector, which accounts for the highest share of greenhouse gas emissions by all sectors. The transition requires a large amount of batteries which bring challenges, not least when it comes to raw material supply and sustainability issues during the mineral mining. Long-term battery recycling is one way to address these challenges. To achieve an efficient recycling process the implementation of lifecycle perspectives in the EV battery pack design phase is of great importance. One of the major activities in the recycling process is the battery disassembly, which requires standardisation and design simplifications to minimize labour time and facilitate automated disassembly. Some of the most important design features is component standardisation, linear pack design and decreased number of parts, including screws, fasteners, and modules, which applies for all pack designs. In recent years new EV battery pack designs have entered the market, which has an improved performance in terms of energy density and cost per kWh. The development of these pack designs is strongly interacting with improvements in the cell design and cell chemistry. The overarching design trend is moving towards battery packs which remove modules, such as Cell-to-pack, and where the battery is integrated as a structural part in the vehicle frame, such as Cell-to-chassis. However, there are uncertainties about the impact of these design trends on the battery disassembly and recycling, which need to be investigated. Comparisons between the new trends and the traditional Module-to-pack design indicate that Cell-to-pack brings advantages to the recycling process as it usually contains less components and does not require labour to disassemble the modules. The chassis-integrated designs need more research to draw general conclusions, but the recyclability may not exceed the Cell-to-pack as the use of structural adhesives and chassis integration likely bring aggravating circumstances on the disassembly. Besides recyclability, the new pack designs also have a strategic impact on the actors in the value chain. EV battery packs with high recyclability should also be in all actors’ interest when moving towards a circular economy, as the recycling cost will be distributed along the entire value chain. / Elektrifiering är en nyckelfaktor för att minska koldioxidutsläppen inom transportsektorn, som står för den största andelen av alla sektorers utsläpp av växthusgaser. Övergången kräver en stor mängd batterier, vilket medför utmaningar, inte minst när det gäller råvarutillgången och hållbarhetsaspekter under mineralbrytningen. Återvinning av batterier är ett sätt att hantera dessa utmaningar långsiktigt. För att uppnå en effektiv återvinningsprocess är det av stor betydelse att tillämpa ett livscykelperspektiv i designfasen för batteripaket i elfordon. En av de viktigaste aktiviteterna i återvinningsprocessen är demontering av batterier, vilket kräver standardisering och förenklad konstruktion för att minimera arbetstiden och underlätta automatiserad demontering. Några av de viktigaste designegenskaperna är komponentstandardisering, linjär design och minskat antal delar, inklusive skruvar, fästelement och moduler, vilket gäller för alla packdesigner. Under de senaste åren har nya batteripackdesigner för elfordon kommit till marknaden, med förbättrad prestanda när det gäller energitäthet och kostnad per kWh. Utvecklingen av dessa batteripack interagerar tydligt med förbättringar inom celldesign och cellkemi. Den övergripande designtrenden går mot batteripack där moduler tas bort, till exempel Cell-to-pack, och där batteriet är integrerat som en strukturell del i fordonsramen, till exempel Cell-to-chassi. Det finns dock osäkerheter gällande designtrendernas påverkan på demontering och återvinning av batterierna, vilket kräver ytterligare undersökning. Jämförelser mellan de nya trenderna och den traditionella konstruktionen Module-to-pack visar att Cell-to-pack medför fördelar för återvinningsprocessen eftersom den vanligtvis innehåller färre komponenter och inte kräver arbete för att demontera modulerna. De chassiintegrerade konstruktionerna kräver mer forskning för att kunna dra några allmänna slutsatser, men återvinningsbarheten överträffar möjligen inte Cell-to-pack designen, eftersom användningen av strukturella lim och chassiintegrering sannolikt leder till försvårande omständigheter vid demonteringen. Förutom återvinningsbarheten har de nya förpackningarna också en strategisk inverkan på aktörerna i värdekedjan. Batteripaket med hög återvinningsbarhet bör även ligga i alla aktörers intresse vid implementering av en cirkulär ekonomi, eftersom återvinningskostnaderna kommer att fördelas över hela värdekedjan.

Thesis deals with the design of a battery box with lithium-ion technology, for the largest possible driving range of the BUT SuperEL II electric car. Based on the analysis of the electric vehicle available space and the parameters of the electronic system, the maximum size of the entire set of 84s130p batteries was designed. 18650 cells with NMC technology were selected due to the very high gravimetric and volumetric density, which reaches 274 Wh/kg and 564 kWh/m3. The total nominal capacity of the designed battery boxes in the electric car is 138 kWh. The total gravimetric energy density of the designed box is 215.6 Wh/kg. It allows the electric car to reach the theoretical range with a consumption of 14 kWh/100 km of almost 1000 km. The individual battery modules of the battery box are controlled for optimal operating conditions by means of a BMS. The whole set is divided into 5 battery boxes. These boxes are manufactured using the technology of bent welded sheets from aluminum alloy EN AW 1050A and steel 1.4301. FEM analyzes were performed to verify the mechanical strength of the designed structure. The work also deals with the design of battery modules and their connection.

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The transient thermal response of a 15-cell, 48 volt, lithium-ion battery pack for an unmanned ground vehicle was simulated with ANSYS Fluent. Heat generation rates and specific heat capacity of a single cell were experimentally measured and used as input to the thermal model. A heat generation load was applied to each battery and natural convection film boundary conditions were applied to the exterior of the enclosure. The buoyancy-driven natural convection inside the enclosure was modeled along with the radiation heat transfer between internal components. The maximum temperature of the batteries reached 65.6 °C after 630 seconds of usage at a simulated peak power draw of 3,600 watts or roughly 85 amps. This exceeds the manufacturer's maximum recommended operating temperature of 60 °C. The pack was redesigned to incorporate a passive thermal management system consisting of a composite expanded graphite matrix infiltrated with a phase-changing paraffin wax. The redesigned battery pack was similarly modeled, showing a decrease in the maximum temperature to 50.3 °C after 630 seconds at the same power draw. The proposed passive thermal management system kept the batteries within their recommended operating temperature range.

Med övergången till elektrifiering inom transport uppstår nya utmaningar när det gäller batterisystem som placeras i elfordon. Det finns för närvarande en möjlighet att minska riskerna med toxiciteten hos partiklar som sprutas ut med de gaser som bildas under termisk rusning i litiumjonbattericeller som är placerade i batterisystem. Syftet med denna avhandling är att identifiera potentiella material för partikelfiltrering från dessa gaser, undersöka de valda materialens prestanda i ett experiment, och föreslå material för framtida studier. Filtermaterialet är avsett att sitta vid ventilen i batteripacket. Totalt valdes 5 filter för experimenten, där 3 av dessa var mikrofiberfilter gjorda av kvarts och 2 var mikrofiberfilter av glas. Filtren klämdes mellan stålplattor med ett hål, och placerades 40 cm ovanför battericellens ventil. Battericellerna utlöstes till termisk rusning och filtren placerades i den direkta vägen för utslungade partiklar för att testa deras termiska motstånd och partikelretentionsförmåga. Filtren karaktäriserades med hjälp av vägning, svepelektronmikroskopi, samt energidispersivt röntgenspektroskopi. Efter ett första test ansågs glasfiberfiltren inte ha tillräckligt hög värmeresistens för att fortsätta testas. Kvartsmikrofiberfiltren varierade i fråga om värmeresistens, där de ibland brann upp och ibland förblev helt intakta. Detta berodde troligtvis till stor del på skillnader i termisk rusning mellan experimenten på grund av varierande uppvärmningsparametrar. Kvalitativt sett lyckades kvartsmikrofiberfiltren fånga upp partiklar, men det kan inte kvantifieras i detta experiment hur effektiva de var när det gäller partikelretention. Filtren visade potential för en enkel tillämpning i batteripacket, men ytterligare forskning bör göras för att undersöka viktiga faktorer, såsom mottryck från filtren. Dessutom finns det vissa material som kan vara intressanta att testa i framtiden, bland annat keramiska material, sintrade metallfiberfiltar och ablativa material. / With the shift towards electrification in transportation, new challenges arise with regards to battery systems placed in electric vehicles. There is an opportunity to reduce risks associated with the toxicity of particles ejected from the gases that form during thermal runaway (TR) in lithium-ion battery cells placed in battery systems. The aim of this thesis is to identify potential materials for particle filtration from these gases, investigate the performance of the chosen materials in an experiment, and suggest materials for future studies. The filter material is intended to sit by the vent in the battery pack. In total 5 filters were chosen for the experiments, where 3 of those were quartz microfibre filters and 2 were glass microfibre filters. The filters were sandwiched between steel plates with a hole, placed 40 cm above the battery cell vent. The battery cells were triggered into thermal runaway, and the filters were placed in the direct path of ejected particles in order to test their thermal resistance and particle retention capabilities. The filters were characterized using weighing, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. From an initial test, the glass fibre filters were deemed not sufficient enough in terms of thermal resistance to continue being tested. The quartz microfibre filters varied in terms of thermal resistance, where they at times burned away and other times remained intact. This was largely attributed to differences in TRs between the experiments due to varying heating parameters. Qualitatively, the quartz microfibre filters succeeded in catching particles, but it cannot be quantified in this experiment how efficient they were in terms of particle retention. The filters showed potential in an easy application in battery packs, but further research should be done to investigate important factors, such as back pressure from the filters. Furthermore, there are certain materials that could be interesting to trial in the future. These include ceramic materials, sintered metal fibre felts, and ablative materials.

This work reports the experimental and numerical study of the thermal management of Li-ion battery packs under the context of electric vehicle (EV) or hybrid EV (HEV) applications. Li-ion batteries have been extensively demonstrated as an important power source for EVs or HEVs. However, thermal management is a critical challenge for their widespread deployment, due to their highly dynamic operation and the wide range of environments under which they operate. To address these challenges, this work developed several experimental platforms to study adaptive thermal management strategies. Parallel to the experimental effort, multi-disciplinary models integrating heat transfer, fluid mechanics, and electro-thermal dynamics have been developed and validated, including detailed CFD models and lumped parameter models. The major contributions are twofold. First, this work developed actively controlled strategies and experimentally demonstrated their effectiveness on a practical sized battery pack and dynamic thermal loads. The results show that these strategies effectively reduced both the parasitic energy consumption and the temperature non-uniformity while maintaining the maximum temperature rise in the pack. Second, this work established a new two dimensional lumped parameter thermal model to overcome the limitations of existing thermal models and extend their applicable range. This new model provides accurate surface and core temperatures simulations comparable to detailed CFD models with a fraction of the computational cost. / Ph. D.

L’électrification des moyens de transport est de plus en plus importante. Sa mise en œuvre nécessite des systèmes de stockage de l’énergie plus performants, moins coûteux, et plus sûrs. Actuellement, les batteries lithium-ion équipent la majorité de ces véhicules innovants. Toutefois, ces systèmes sont complexes, onéreux, et leur performance se dégrade au cours du temps. Leur durabilité constitue donc un enjeu majeur.Son estimation est complexe car elle ne dépend pas que des kilomètres parcourues mais des conditions d’usage. Actuellement, les outils de prédiction de durée de vie des batteries sont simplificateurs ou pas compatible avec l’usage automobile.L’objet de ces travaux consiste à développer un outil de simulation capable de reproduire le comportement électrique, thermique, et de vieillissement d’un pack batteries au cours de sa vie. Cet outil doit permettre l’optimisation de la conception et l’usage des packs afin d’augmenter leur durabilités. Des campagnes d’essais ont permis de calibrer et de valider des modèles électrothermiques au niveau de la cellule puis à l’échelle de l’assemblage. De même, la mise en place et l’analyse de tests de vieillissement accélérés ont permis de développer une loi de vieillissement et de mettre en avant un optimum d’usage.Le comportement du pack a été par la suite testé dans différentes conditions d’usage par l’intermédiaire d’un simulateur de scénario. Des stratégies de conception et de recharges ont été donc proposées et vérifiées par simulation. / Lithium batteries are key solutions as power storage systems for several applications including portable devices, aviation, space, and electrified vehicles. Their success is principally due to their high power and energy density. Therefore, several researchers are attempting to develop more powerful, cheaper, longer-lived and more secure batteries. One drawback of lithium batteries is their durability: lithium batteries’ energy and power capability decrease over time. The degradation rate is sensitive to operating conditions. A crucial step towards the large-scale introduction of electrified vehicles in the market is to reduce the cost of their energy storage devices.The aim of this study is to develop a simulation tool at the pack level able to reproduce its electro-thermal-aging behavior overtime. Thanks to an accelerated aging tests and experimental approach the models are calibrated and coupled with a usage scenario simulator at the vehicle level. The behavior of the pack is thus studied under different conditions and simulations were compared and discussed. Strategies of usage and charging were then proposed and validated by simulation.