1,721,003 research outputs found
Hardware-in-the-Loop Platform for Assessing Battery State Estimators in Electric Vehicles
Full text linkThe development of new algorithms for the management and state estimation of lithiumion batteries requires their verification and performance assessment using different approaches and tools. This paper aims at presenting an advanced hardware in the loop platform which uses an accurate model of the battery to test the functionalities of battery management systems (BMSs) in electric vehicles. The developed platform sends the simulated battery data directly to the BMS under test via a communication link, ensuring the safety of the tests. As a case study, the platform has been used to test two promising battery state estimators, the Adaptive Mix Algorithm and the Dual Extended Kalman Filter, implemented on a field-programmable gate array based BMS. Results show the importance of the assessment of these algorithms under different load profiles and conditions of the battery, thus highlighting the capabilities of the proposed platform to simulate many different situations in which the estimators will work in the target application
Improvement of Sodium-Metal Halide Battery Electrical Equivalent Model Including Temperature Dependency
No full textSodium-Metal Halide Batteries are a very promising alternative to the Lithium-ion ones for stationary applications, but their chemical complexity requires an accurate battery model to optimize their use. The electrical equivalent model of the battery is ordinarily used to this aim. The temperature dependency of the model parameters is studied in this work. Three characterization tests are carried-out at 270, 300, and 330
and analyzed to identify the model parameters. The parameters obtained are then compared with the literature showing that introducing in the model the temperature dependency can improve the accuracy of about six times
A Novel and Robust Security Approach for Authentication, Integrity, and Confidentiality of Lithium-ion Battery Management Systems
Full text linkBattery management systems (BMSs) play a critical and crucial role in ensuring the safety and the efficiency of the batteries. The increasing BMS complexity, the expanding interconnections between batteries and applications, and the introduction of cloud-based energy storage system structures have led to growing concerns about battery cybersecurity. For instance, the data exchange between the local and remote BMS parts can be exposed to cybersecurity attacks. Classic BMSs are not equipped with security mechanisms that are instead essential to protect their integrity and reliability and prevent serious consequences such as loss of data, equipment damage, and counterfeiting of battery components. This work highlights the importance of securing BMSs against cyber threats and discusses the current state of the art of cybersecurity in BMSs. The main outcome is the proposal of a novel and robust security approach to design a BMS able to prevent misuse and undesired manipulation of battery equipment and data. The proposed design approach can be used as enabling technology to support the application to the BMSs of the most diffused security mechanisms adopted by the state of the art as cybersecurity protections
Electrical Circuit Model for Sodium-ion Batteries
No full textSodium-ion batteries offer a promising alternative to lithium-ion ones thanks to their lower cost, smaller ecological footprint, and less stringent safety requirements. The development of an accurate model to reproduce their behaviors is still an open issue, despite being essential for enabling their efficient utilization. This work investigates the repurposing of lithium-ion equivalent circuit models for sodium-ion cells. Four models with 1, 2, 3, and 4 RC groups are considered to investigate their trade-off between accuracy and computational efficiency. The model parameters are identified with a pulse current test carried out on two nominally identical commercial cells.
The performance of the models is evaluated using pulse current tests and a realistic electric vehicle current profile. In both cases, all the models achieve errors lower than 1% of the nominal cell voltage. These values are comparable with those obtained in lithium-ion cell models, suggesting the portability of model-based algorithms from lithium-ion batteries to sodium-ion ones. Moreover, the results highlight that the model with 2 RC groups is the best choice in low computational complexity systems. On the other hand, the model with 3 RC groups has the best trade-off between accuracy and computational complexity
Analysis of Thermal-Induced Shunt Current Sensor Errors in a Low-Cost Battery Management System
No full textLithium-Ion batteries are becoming a standard solution for automotive applications. These batteries must be equipped with a Battery Management System that monitors and controls the battery avoiding hazardous situations. The battery current measurement is crucial for both safety and control tasks. Shunt-based current sensors are widely used in automotive applications, thanks to the affordability and linearity of the measurement. This article discusses an unexpected current measurement error occurred during the test of a prototypal Battery Management System for a 12 V cranking battery. The current error only shows up during the cell balancing procedure, pointing to a thermal related effect. A theoretical assessment of the problem suggests the thermoelectric effect as the best candidate to explain the error. The thermal simulation of the circuit validated the hypothesis with perfect match. Finally, the guidelines for a correct shunt choice in a Battery Management System are provided
A novel methodology to study and compare active energy-balance architectures with dynamic equalization for second-life battery applications
Full text linkThe continuous growth of the electric vehicles market and the increasing environmental awareness impose to search for innovative solutions to reuse the exhausted vehicle batteries in different applications. One of the main problems of second-life batteries is the very high mismatch among their cell capacities which reduces the overall battery performance. The mismatch effect can be overcome by using dynamic equalization. This technique aims to keep balanced as much as possible the State of Charge of the cells during the battery operation, i.e. in both the charge and discharge phases. In order to do this, the dynamic equalization approach requires a high-current active energy balancing system able to move a quantity of charge among the battery cells much higher than the active balancing circuits sometimes used in first-life batteries. The use of a high equalization current increases the design complexity of the balance system.
A methodology to study and compare the main balance system topologies suitable for second-life batteries with dynamic equalization approach is presented in this work. The Adjacent Cell-to-Cell, Direct Cell-to-Cell, Cell-to-Pack, and Pack-to-Cell active balance topologies are analyzed considering the case study of a second-life battery composed of 10 series-connected cells with capacity values uniformly distributed around
15 % of the nominal value.
The investigation proves that the Direct Cell-to-Cell topology has the best performance. This balancing topology improves the usable battery capacity of around 16 % with respect to the case in which no dynamic equalization is applied if a DC/DC converter with a power efficiency of only 70 % is used. Finally, the results show that the Adjacent Cell-to-Cell performance is strongly affected by the position of the cell mismatches in the battery
Implementation of the fast charging concept for electric local public transport: The case-study of a minibus
Full text linkThis paper shows an effective implementation of the fast charging concept in the electric local public transport context. An electric minibus powered with a lead-acid battery is considered as a case-study. Its traction battery is redesigned using 12 V standard lithium-iron-phosphate modules to benefit from the higher performance of the lithium battery technology compared to the lead-acid one. The minibus can achieve a continuous operation characterised by 20 min of traveling alternated with 10 min of standstill for fast recharging of the battery. Experiments performed on a single module of the battery show that the load profile is sustained without appreciable issues both in temperature and life degradation of the lithium cells
A Dynamic Equalization Topology Based on Auxiliary Cell: Theoretical and Simulative Analyses
No full textThe dynamic equalization approach can significantly increase the use of electric vehicle second-life batteries in stationary applications. Dynamic equalization aims to face the very high variability of the capacity values of the second-life battery cells that strongly reduces the battery usable capacity. This work proposes an alternative dynamic equalization architecture based on an auxiliary cell to support the less-performing cells, maximizing the battery usable capacity. A theoretical methodology has been presented to analyze the proposed architecture. The obtained preliminary theoretical results are then validated using a simulation platform. The final results show a potential increase in usable battery energy of up to 16 % using an ideal DC/DC converter, and 13 % with a DC/DC converter efficiency of 0.8
Aging-Aware Electric Vehicle Simulation Platform for Battery Charging Strategy Optimization
No full textThe constant growth of the electric vehicles market is exposing the open issues related to battery management. One of them is the need for long recharging time compared with the refueling of thermal vehicles. Several fast-charging protocols have been developed and studied in the literature aiming to mitigate this issue. However, fast-charging involves high charging current and determines consistent heat generation, causing detrimental effects on battery health and premature aging of electric vehicle batteries. This paper proposes a simulation platform developed in Matlab-Simulink environment that embeds a vehicle model and a battery model including thermal, electrical, and aging phenomena. The aim is to evaluate the performance of the charging protocols and estimate their effects on battery health in a realistic scenario. A case study was considered to assess the functionalities of the platform. A year of daily usage of an electric vehicle with typical driving and different fast charging profiles was simulated. The results highlight the battery health degradation due to the specific usage profile, charging protocols, and thermal-related issues. Moreover, the results suggest that the proposed platform could serve as a preliminary benchmark in designing optimized fast-charging protocols
Low-Cost Lithium-Ion Battery Characterization Setup Based on Auxiliary Batteries
No full textCharacterization tests are key to improve the Lithium-Ion batteries performance. Unfortunately, they require expensive equipment that small companies and laboratories can hardly afford. In this paper a novel low-cost battery characterization setup is proposed. It uses an auxiliary battery to strongly reduce the required maximum instrument power and cost. A simulation framework of the proposed setup is developed in Matlab/Simulink environment and is applied to the characterization of a 48 V mild hybrid battery. This case study is used to both explore setup advantages and guide through its sizing. The obtained results show a strong reduction of the power required to the test equipment and a reduction up to about 70% of the energy drawn from the grid
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