Estimating Battery Pack SOC Using A Cell-to-Pack Gain Updating Algorithm
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Abstract:
Lithium-ion batteries are becoming the main energy storage in electric vehicles and electric grids. To elevate the battery capacity and the voltage supply, the battery cells are stacked to form a battery pack. The state-of charge (SOC) of the battery pack requires continuous monitoring for the operation safety. The current developed SOC estimation algorithms shows decent estimation accuracy but they are designed for individual cells. These algorithms stay in the battery cell level because they cannot capture the cell-to-cell difference which exists after manufactured. This paper proposed a battery pack SOC Co-Estimation algorithm based on the estimated battery cell SOC. The proposed battery pack SOC Co-Estimation algorithm can accurately estimates the SOC of a battery pack with three serial connected battery cells but without cell balancing. This algorithm also has the potential to reduce the computation effort on the battery management system (BMS) because it does not need to monitor every single cell in the battery pack.Keywords:
Battery pack
State of charge
Accurate estimations of cell state-of-charge (SoC) for multi-cell series-connected battery pack are remaining challenge due to the inconsistency characteristic inhabited in battery pack and the uncertain operating conditions in electric vehicles. This paper tries to add three contributions. (1) A data-driven filtering process is proposed to select one represented cell to typify the voltage behavior of battery pack. (2) An improved battery model considering model and parameter uncertainties is developed. (3) An adaptive SoC estimator has been developed, in which the SoC of each cell in battery pack can be accurately predicted. The SoC of battery pack can be located with the SoC values of each cell. It significantly improves the safety operation of battery. The result indicates that the estimation errors of voltage and SoC for all the LiPB cells are less than 3% even if given big erroneous initial state of estimator.
Battery pack
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Abstract: Unique Electric vehicles are most well known nowadays. EV's are the best vehicles for transportation. Electrical vehicles industry going to blast in India. It will happen on the grounds that India is a home all things considered dirtied urban areas on the planet additionally EV energy wises multiple times more energy productivity when contrasted with ICE vehicle and it has multiple times less parts. The Battery System, which is the core of EVs, comprises of cells, Battery Modules and Battery Packs that are acknowledged by joining battery modules. With the quick improvement of Lithium-Ion Battery Technologies in the electric vehicles (Ev's) industry, The lifetime of the battery cell increments significantly. For changing over the ICE vehicles into Electrical vehicle its fundamental to make the battery pack for that vehicle. For building or fostering the Battery pack we need to think about such countless things. Keywords: Li-Ion Battery cells, Battery Pack Structural design, Thermal Design, Cooling System, Battery Management System (BMS), Safety Majors.
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Depending on the application, power and energy requirements may differ significantly and, most likely, a single lithium-ion cell will not suffice. Battery packs offer cell interconnections that allow to obtain several possible voltage and discharge current ratings. Typically, the battery packs are designed to meet the specifications of the application within a certain range, and sometimes they are oversized just to consider degradation effects that may affect battery performance in the long term. However, operating a battery pack at different ranges for the state-of-charge and temperature, among other variables, might have a major impact on its lifespan. This paper, introduces a technique on how a modular battery pack can be designed in terms of extending the lifespan of the energy storage device, where each battery module has different capacity ratings. The available energy on each module of the battery pack is constrained and controlled to meet the electric demand, ensuring optimal ranges for the state-of-charge. Also, the article shows that it is possible to meet energy requirements with the modular battery pack at a lower cost than just a single module battery pack.
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Lithium ion (Li-ion) battery life and performance significantly depend on operating temperature and usage. There are four battery characteristics that are interlinked: Life, capacity, operating temperature, and usage. The goal of battery pack design is to minimize the battery pack cost or to maximize the battery pack life or both if possible. This paper develops a model based process that selects battery operating temperature and capacity to optimize the life and cost of the battery pack under prescribed usage. Simulations using experimentally validated performance and aging models demonstrate that for a particular application, battery cost can be reduced by 30% if the battery pack is operated at 45° C. Also there exists an optimal battery pack size for a specified battery temperature, and over-sizing the battery pack does not further increase the battery life.
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Abstract Efficiency of the battery pack largely depends on the resistive losses and heat generation between the interconnections of the battery cells. Grouping of battery cells usually is done in different ways in industries. However, losses vary depending on applications or states of electric vehicle (EV). Therefore, it is necessary to determine the efficiency and heat generation in battery cells as well as battery packs. In practical situations, some battery cells are charged rapidly in comparison to other battery cells. On the other hand, when an EV is in running condition some battery cells are discharged rapidly. As a results battery pack cannot provide better efficiency and its life span is reduced. As an alternative option the inter-cell connection of battery package is needed to reconfigure in an optimized way. In this paper firstly, a battery pack with switches is modeled and then efficiency and temperature variation with respect to time are determined. Then, an experimental setup is investigated to measure the efficiency and temperature rise with respect to time. Results, explained in the paper, demonstrate that battery pack with switches increases the efficiency if it is measured after switching (97–98 %), while temperature increases from 25 °C to 50 °C for different C-rates.
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The existing electric ATV in the Automotive Laboratory, P21 of UniversitiTeknologi Malaysia had left abandoned without any purpose due to the lack of a battery. Therefore, developing a battery pack for the electric ATV using the 40 Ah lithium-ion pouch cells can make the electric ATV functional again. To do this, the battery needs to be designed in a way that it can fit inside the cargo load of the ATV which is the space of the previous battery. Next, the capacity of the battery pack needed to be designed based on the requirement of the electric ATV existing in the automotive laboratory. The complete system of the battery must include cooling system, battery management system (BMS), charging system and the battery packaging. Finally, the objectives of this project are achieved whereby a good performance battery with 74 V 80 Ah of capacity equipped with cooling system, battery management system, charging system and battery packaging is successfully developed.
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Increasing the life cycle of battery packs is one of the most valuable endeavors in modern Li-ion battery technologies, especially for light electric vehicles whose material costs are often significantly determined by the costs of the battery pack. The main aim of the present study is to help manufactureres of LEV's to circumvent the type of discharge profiles that substantially degrade the LEV's battery pack. To this end, this paper describes a measurement setup in which various discharge patterns from light electric vehicles, acquired during actual use of the vehicles, are simulated in a lab environment in order to assess their influence on the degradation of the Li-ion battery packs. The results of these measurements can be used to optimize discharge profiles and improve battery management systems with the aim to extend the Li-ion battery life time.
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