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Hybrid fuel cell powertrains are a promising strategy to reduce the environmental impact of vehicles and non-road mobile machinery. To preserve the state-of-health of fuel cells, an energy storage system with sufficient power capacity, such as ultra-capacitors or batteries, should be introduced in the system to help the fuel cell during sudden and abrupt changes in power demands. However, the presence of two or more energy sources necessitates the development of an energy management strategy. The energy management strategy should properly split the power request between the different energy sources. In this paper, the design and the experimental validation of a scaled test bench for the emulation of a fuel cell/battery powertrain for a vehicular application is presented. The fuel cell is emulated through an analogically controlled DC power source that reproduces its real voltage–current curve. To split the power between the emulated fuel cell and the batteries, controlled DC-DC is used and a simple energy management strategy based on a proportional-integral controller is developed. The external load is reproduced using a load unit composed of a programmable electronic load and a power supply. Experimental tests are performed to evaluate the system behaviour and to characterize its main components. The experimental results show that the system successfully emulates the powertrain in accordance with the proposed energy management strategy. [ABSTRACT FROM AUTHOR]

Nowadays, lithium-ion batteries are one of the most widespread energy storage systems, being extensively employed in a large variety of applications. A significant effort has been made to develop advanced materials and manufacturing processes with the aim of increasing batteries performance and preserving nominal properties with cycling. Nevertheless, mechanical degradation is still a significant damaging mechanism and the main cause of capacity fade and power loss. Lithium ions are inserted and extracted into the lattice structure of active materials during battery operation, causing the deformation of the crystalline lattice itself. Strain mismatches within the different areas of the active material caused by the inhomogeneous lithium-ions concentration induce mechanical stresses, leading ultimately to fracture, fatigue issues, and performance decay. Therefore, a deep understanding of the fracture mechanics in active materials is needed to meet the rapidly growing demand for next-generation batteries with long-term stability, high safety, excellent performance, and long life cycle. This review aims to analyze the fracture mechanics in the active material microstructure of electrodes due to battery operations from an experimental point of view. The main fracture mechanisms occurring in the common cathode and anode active materials are described, as well as the factors triggering and enhancing fracture. At first, the results obtained by performing microscopy and diffraction analysis in different materials are discussed to provides visual evidence of cracks and their relation with lattice structure. Then, fatigue phenomena due to crack growth as a function of the number of cycles are evaluated to assess the evolution of damage during the life cycle, and the effects of fracture on the battery performance are described. Finally, the literature gaps in the characterization of the fracture behavior of electrode active materials are highlighted to enhance the development of next-generation lithium-ion batteries. [ABSTRACT FROM AUTHOR]

In this article, the attention is focused on a specific battery testing methodology for high-power hybrid electric working vehicle applications. Due to the high power demand, a deep knowledge of the battery behaviour is necessary and requires specific testing procedures, different from the standard activities available in the literature for the automotive field. In this article, the attention focused on the power demand that an energy storage system must satisfy to achieve a certain performance, considering this testing approach closer to the real application. A numerical model of a full electric telescopic handler developed in previous works was used to test a LiFePO4 cell in a hardware-in-the-loop bench test configuration. The output voltage–current characteristic was compared with the same output generated by the numerical model of the considered battery. The same model was then tested according to a handling working cycle proposed by the authors for a telescopic handler derived from the experience of the research group in the field of this type of vehicles. This mission profile was then used to evaluate the performance of the proposed battery pack configuration in a real working scenario and at different SoC levels. [ABSTRACT FROM AUTHOR]

In this work, a comparative numerical analysis between the performance of a conventional specialized orchard tractor and those of three different hybrid electric tractor configurations is presented. The aim was to compare several powertrain configurations in the same working scenarios derived from field measurements. Peak power capabilities and endurance were numerically tested with specific load scenarios involving both transportation mission profiles and field activities with external implements powered through the power take off of the tractor. The proposed hybrid architectures were configured with the same battery-based energy storage system to perform the comparison with the same energy storage capabilities. Two parallel, two series and one electro-hydraulic hybrid configuration were modeled and tested through simulations. The parallel ones excelled in peak power performance, whereas the series configurations had the highest fuel savings. The electro-hydraulic configuration was proposed as an alternative able to allow for a downsized engine but also for the introduction of the Continuously Variable Transmission (CVT) functionality, which is always an interesting feature for such working machines. [ABSTRACT FROM AUTHOR]

Lithium ion batteries are one of the most widespread energy storage systems, but they still suffer some weak points, such as safety, limited energy density, and cycle life. The latter is caused by electrochemical and mechanical damaging mechanisms. The mechanical damaging mechanisms and their interplay with electrochemistry are reviewed in this paper. Lithium ions are inserted and extracted in the active materials of electrodes during battery operation, causing the deformation of the electrode microstructure. The deformation causes stresses and fractures ultimately, inducing electrochemical reactions on the crack surfaces, which lead to performance decay, such as loss of capacity and power. Then, proper mechanical models are needed to evaluate stress and crack propagation during battery operation. This review aims to give a comprehensive explanation of the following subjects: (a) The most general electrochemical–mechanical and transport models for intercalation materials; (b) Fundamentals of fracture mechanics; (c) Numerical implementation of fracture mechanics models applied to lithium ion batteries, covering the different approaches used in literature to estimate fracture in static and dynamic conditions; (d) Summary of the results of fracture mechanics models for lithium ion batteries; (e) Degradation models based on fracture mechanics. • Stress computation in active material and coupling with transport equations. • Fundamentals of fracture mechanics models: LEFM, phase-field model and cohesive zone model. • How to implement fracture mechanics models when dealing with LIBs. • Literature results: fracture maps, stability conditions, crack path and fatigue. • Relation between capacity fade and fracture mechanics. [ABSTRACT FROM AUTHOR]