• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1759-1768
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• 2018

The energy density, power density and ohm resistance of battery change significantly as results of battery aging, which lead to decrease in the accuracy of the equivalent model. A parameter identification method of the equivale6nt circuit model with 3 R-C branches based on the test database of battery life cycle is proposed in this paper. This database is built on the basis of experiments such as updating of available capacity, charging and discharging tests at different rates and relaxation characteristics tests. It can realize regular update and calibration of key parameters like SOH, so as to ensure the reliability of parameters identified. Taking SOH, SOC and T as independent variables, lookup table method is adopted to set initial value for the parameter matrix. Meanwhile, in order to ensure the validity of the model, the least square method based on variable forgetting factor is adopted for optimizing to complete the identification of equivalent model parameters. By comparing the simulation data with measured data for charging and discharging experiments of Li-ion battery, the effectiveness of the full life cycle database and the model are verified.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.12
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• pp.113-118
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• 2020

Recently, eco-friendly electric motorcycles have been considered to replace aging gasoline motorcycles to reduce the amount of suspended fine dust in air. However, existing rechargeable battery-powered electric motorcycles have been found unacceptable by users because of their many limitations, such as long charging time, short travel distance per charge, and low driving speed. To overcome the drawbacks of conventional electric motorcycles, this paper proposes an exchangeable battery-powered electric motorcycle and a new frame shape for housing the exchangeable battery. The proposed frame is similar to that of current electric motorcycles; however, the shape and position of the saddle support, battery, and controller mount section are redesigned. The safety of the presented frame is verified through static and dynamic analyses using ABAQUS. In particular, the dynamic analysis is conducted under the most extreme condition among the various operating situations, thus confirming the robustness of the proposed frame design.

• Korean Chemical Engineering Research
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• v.59 no.3
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• pp.393-398
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• 2021

In order to optimize the performance of a lithium-ion battery, a performance prediction modeling technique that considers various degradation factors is required. In this work, mathematical modeling was carried-out to predict the change in discharging behavior and cycle life, taking into account the cycle aging of lithium-ion batteries. In order to validate the modeling, a cycling test was performed at the charge/discharge rate of 0.25C, and discharging behavior was measured through RPT (Reference Performance Test) performed at 30 cycle intervals. The accuracy of cycle life prediction was improved by considering the break-in mechanism, one of the phenomena occurring in the BOL (beginning of life), in the model for predicting the cycle life of lithium-ion batteries. The predicted change in cycle life based on the model was in good agreement with the experimental results.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.29-38
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• 2017

This paper presents a study on the state-of-charge (SOC) reference based active cell balancing in real-time. The optimal references of SOC are determined by using the proposed active cell balancing system with the bidirectional DC/DC converters via the dual active bridge (DAB) type. Then, the energies between cells can be balanced by the power flow control of DAB based bidirectional DC/DC converters. That is, it provides the effective management of battery by transferring energy from the strong cell to the weak one until the cell voltages are equalized to the same level and therefore improving the additional charging capacity of battery. In particular, the cell aging of battery and power loss caused from energy transfer are considered. The performances of proposed active cell balancing system are evaluated by an electromagnetic transient program (EMTP) simulation. Then, the experimental prototype is implemented in hardware to verify the usefulness of proposed system.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.4
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• pp.316-324
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• 2022

This paper uses seasonal auto-regressive integrated moving average (S-ARIMA), which is efficient in seasonality between time-series models, to predict the degradation tendency for lithium-ion batteries and study a method for improving the predictive performance. The proposed method analyzes the degradation tendency and extracted factors through an electrical characteristic experiment of lithium-ion batteries, and verifies whether time-series data are suitable for the S-ARIMA model through several statistical analysis techniques. Finally, prediction of battery aging is performed through S-ARIMA, and performance of the model is verified through error comparison of predictions through mean absolute error.

• Proceedings of the Korean Society of Computer Information Conference
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• 2022.07a
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• pp.149-152
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• 2022

최근 전기차의 기술 발전이 급속도로 증가함에 따라 이차전지의 수요가 증가하게 되었다. 그로인해 다량의 고품질 전지를 생산하기 위해 제조 공장이 가동되고 있지만 생산된 전지의 품질의 핵심이 되는 화성공정의 에이징 과정 진행 중 온도 관리에 실패할 경우, 전지의 폭발 및 화재의 위험이 있다. 본 논문은 이차전지를 생산하는 에이징 공정의 효율적인 온도 관리를 위해 목업 모형을 만들어 온도 센서를 통한 온도 수집 및 모니터링 시스템을 개발하고, 공조기 바람을 통해 전지의 온도가 변화하는 속도를 계산하고, 이상온도에 도달해 고온의 상태가 되었을 경우 주변 전지로 전달되는 열을 시뮬레이션 통한 효율적인 공조 대책을 제시하여 이차전지 생산의 품질 향상과 화재 예방을 통해 전기차 생산에 따른 리튬이온 전지의 수요 해결에 기여한다.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.2
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• pp.149-155
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• 2016

In this study, we investigated the adhesive strength by molecular weight, mixture ratio, coating thickness, lamination temperature and aging condition of adhesive in manufacture process of Nylon-Aluminum for secondary aluminum pouch. It found that as the molecular weight of adhesive gets lower, the adhesive strength increases. In the mixture ratio, as the content of hardener get higher and as the content of solvent get lower, the adhesive strength increases. Also, as the coating thickness of adhesive get thicker, the adhesive strength increase. In addition, the adhesive strength is higher at 90 degrees of lamination temperature. So, it found that 90 degrees of lamination temperature is appropriate. In the aging condition when aged for 5 days, it found that the reaction and curing of adhesive is sufficient by measuring the adhesive strength.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.2
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• pp.223-229
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• 2023

Seawater batteries are next-generation secondary batteries that use seawater as a cathode. They utilize marine resources to provide competitive prices, high eco-friendliness, and a structure suitable for marine applications. Based on these advantages, pouch types and prismatic types have been studied and developed assuming natural seawater exposure. However, because of the electrical characteristics of the secondary battery, its capacity and internal resistance vary depending on the use environment. These characteristics are not only utilized for predicting the life of a battery but also have a direct effect on the capacity and power suitable for a specific situation. Therefore, the internal resistance was analyzed in this study by measuring the capacity depending on the seawater battery use environment and the state-of-charge-open-circuit-voltage measurement method.

• Journal of IKEEE
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• v.27 no.4
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• pp.477-485
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• 2023

In this paper, the effect of AC ripple on the lifetime of lithium-ion batteries is experimentally analyzed. Bidirectional power conversion system(PCS) is used to increase the efficiency of energy storage systems (ESS). When connected to the grid, a current ripple with a frequency twice the grid frequency is applied to the battery due to its structure. Therefore, to analyze the effect of AC ripple on Li-ion battery aging, cycle life test are performed by applying charge/discharge profiles of DC current and DC+AC current ripple specifications. Based on the experimental results, direct current internal resistance (DCIR), incremental capacitance (IC), and surface temperature were analyzed. As a result, it is confirmed that AC ripple does not directly affect degradation and that battery degradation slows down after a certain cycle. These results can serve as a guideline for optimizing filters to reduce ripple on the battery side in applications where AC ripple occurs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.585-593
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• 2020

Until now, 29 fire accidents have occurred; 22 of them were caused by the interconnection of renewable energy sources that occurred during the rest period after the lithium-ion battery had been fully charged regardless of the seasons. The fire accidents of ESS were attributed to thermal runaway due to the overcharging of a few cells with the phenomenon of self-energy balancing, which is unintentional current flow from cells with a high SOC to the low cells if the SOC condition of each cell connected in parallel is different. Therefore, this paper proposes a novel configuration and operation algorithm of the BMS to prevent the self-energy balancing of ESS and presents a hybrid SOC estimation algorithm. From the test results of the self-energy balancing phenomenon between aging and normal cells based on the proposed algorithm and BMS, it was confirmed the possibility of self-energy balancing, which is unintentional current flow from cells with a high SOC to cells with a low SOC. In addition, the proposed configuration of the BMS is useful and practical to improve the safety of lithium-ion batteries because the BMS can reliably disconnect a parallel connection of the cells if the self-energy balancing current becomes excessively high.