• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.1
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• pp.1-8
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• 2021

For the safe and reliable operation of lithium-ion batteries in electric vehicles or energy storage systems, having accurate information of the battery, such as the state of charge (SOC), is essential. Many different techniques of battery SOC estimation have been developed, such as the Kalman filter. However, when this filter is applied to multiple batteries, it has difficulty maintaining the accuracy of the estimation over all cells owing to the difference in parameter values of each cell. The difference in the parameter of each cell may increase as the operation time accumulates due to aging. In this paper, a novel deep neural network (DNN)-based SOC estimation method for multi-cell application is proposed. In the proposed method, DNN is implemented to determine the nonlinear relationships of the voltage and current at different SOCs and temperatures. In the training, the voltage and current data obtained at different temperatures during charge/discharge cycles are used. After the comprehensive training with the data obtained from the cycle test with a cell, the resulting algorithm is applied to estimate the SOC of other cells. Experimental results show that the mean absolute error of the estimation is 1.213% at 25℃ with the proposed DNN-based SOC estimation method.

• Korean Journal of Metals and Materials
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• v.49 no.2
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• pp.174-179
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• 2011

We investigated the surface morphology changes of a lithium/sulfur battery using multi-walled canbon nanotube added sulfur electrode during charge-discharge cycling. The Li/S cell showed the first discharge capacity of 1286 mAh/g-S, which utilized is 71% of the theoretical value. It decreased to 328 mAh/g-S at the 100th cycle, which corresponds to about 19% utilization of the total sulfur in the cathode. The spherical lumps of the reaction product were observed on the surface of the sulfur electrode. This material was verified as lithium sulfide by X-ray diffraction measurement. The pores in the separator were filled with reaction product. Thus the diffusion of the $Li^+$ ion decreased, which resulted in the decreased capacity of the Li/S cell.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.12
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• pp.1889-1894
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• 2017

Global automobile manufacturers are developing electric vehicles (EVs) to eliminate the pollutant emissions from internal combustion vehicles and to minimize fossil fuel consumptions for the future generations. However, EVs have a disadvantage of shorter traveling distance than that of conventional vehicles. To answer this shortfall, more batteries are installed in the EV to satisfy the consumer expectation for the driving range. However, as the energy capacity of the battery mounted in the EV increases, the amount of heat generated by each cell also increases. Naturally, a better battery thermal management system (BTMS) is required to control the temperature of the cells efficiently because the appropriate thermal environment of the cells greatly affects the power output from the battery pack. Typically, the BTMS is divided into an active and a passive system depending on the energy usage of the thermal management system. Heat exchange materials usually include gas and liquid, semiconductor devices and phase change material (PCM). In this study, an application of PCM for a BTMS was investigated to maintain an optimal battery operating temperature range by utilizing characteristics of a PCM, which can accumulate large amounts of latent heat. The system was modeled using Dymola from Dassault Systems, a multi-physics simulation tool. In order to compare the relative performance, the BTMS with the PCM and without the PCM were modeled and the same battery charge/discharge scenarios were simulated. Number of analysis were conducted to compare the battery cooling performance between the model with the aluminum case and PCM and the model with the aluminum case only.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.6
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• pp.732-741
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• 2018

In order to maximize the usable capacity of a BMS (battery management system) that uses several battery cells connected in series, a cell balancing technique that equips each cell with the same voltage is needed. In the active cell balancing circuit using a multi-winding transformer, a balancing circuit that transfers energy directly to the cell (cell-to-cell) is composed of a PMOS switch and a gate driving chip for driving the NMOS switch. The TLP2748 photocoupler and the TLP2745 photocoupler are required, resulting in increased cost and reduced integration. In this paper, instead of driving PMOS and NMOS switching devices by using photocoupler, we proposed 70V BCD process based PMOS gate driving circuit, NMOS gate driving circuit, PMOS gate driving circuit and NMOS gate driving circuit with improved switching time. ${\Delta}t$ of the PMOS gate drive switch with improved switching time was 8.9 ns and ${\Delta}t$ of the NMOS gate drive switch was 9.9 ns.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1740-1749
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• 2009

As mobile devices evolve and digital convergence trend is here to stay, mobile phones are built with multiple functions including cameras, MP3s, TVs and game consoles. As a consequence, such multi-functional mobile phones come to spend more power, facilitating development of next-generation ultra-capacity lithium ion battery. In addition, environmental regulations and rising oil prices cause demand for hybrid cars to keep rising. Accordingly, more and more attention is being paid to medium and large batteries and more efforts are being made to realize lower battery prices, higher outputs and stability. This study presented a patent technology related to the lithium ion battery packing that allows reducing processes related, increasing productivity and recycling parts other than the body. The lithium ion battery pack to which protection circuits are elastically attached provides short circuit protection for the circuit and the body and makes electric connection of the circuit and the body easier.

• Journal of Energy Engineering
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• v.11 no.3
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• pp.254-261
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• 2002

The fabrication method for the main components of the polymer electrolyte membrane fuel cell stack such as electrodes, membrane-electrode assemblies, and bipolar plates was established for the effective electrode area of 240 ㎠. A counter-flow type 100-cell stack was fabricated by using the above components and then a maximum power of 7.44 kW for H$_2$/O$_2$ and 5.56 kW for H$_2$/air could be obtained at 70$\^{C}$ and 1 atm. It was seen that the distribution of the OCV for unit cells in the stack was uniform but the voltage deviation increased as the load increased due to the IR drop and the electrode polarization. The stack was applied to the power source of the fuel cell/battery hybrid electric golf car. It produced about 1 kW at a room temperature operation during the test run, which occupied about 43% of the total power required by the 2.3 kW motor.

• Journal of Power Electronics
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• v.3 no.4
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• pp.230-238
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• 2003

Electric vehicles (EV) demands for greater acceleration, performance and vehicle range in pure electric vehicles plus mandated requirements to further reduce emissions in hybrid electric vehicles (HEV) increase the appeal for combined on-board energy storage systems and generators. And the power electronics plays an important role in providing an interface between fuel cells (FC) and loads. This paper deals with a multiple input DC-DC power converter devoted to combine the power flowing of multi-source on energy systems. The multi-source is composed of (i) FC system as a prime power demands, (ii) super capacitor banks as energy storage devices for high and intense power demands, (iii) superconducting magnetic energy storage system (SMES), (iv) multiple input DC-DC power converter and (v) a three phase inverter-fed permanent magnet synchronous motor as a drive. In this system, It is used super capacitor banks and superconducting magnetic energy replaces from the battery system. The modeling and transient performance simulation is effective for reducing transient influence caused by sudden charge of effective load. The main purpose of power electronic converters is to convert the DC power output from the fuel cell and other to a suitable AC voltage, which can be connected to electric loads directly (PMSM). The fuel cell and other output is connected to the DC-DC converter, which regulates the DC link voltage.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.5
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• pp.469-473
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• 2009

We present high-voltage liquid-electrolyte microbatteries, inspired from the high-voltage generation mechanism of electric eels using serially connected multiple-cell arrays. In the microbatteries, we purge air into the electrolyte filled in a channel layer to isolate serially connected multiple cell arrays using three surface-tension valves (cell-front, outlet, and cell-end valves). Compared to the previous multi-cell stack or interconnection, present microbatteries provide a reduced multi-cell charging time. We have designed and characterized four different prototypes C1, C10, C20, and C40 having 1, 10, 20, and 40 cells, respectively. In the experimental study, the threshold pressures of cell-front, outlet, and cell-end valves were measured as $460{\pm}47$, $1,000{\pm}53$, and $2,800{\pm}170$ Pa, respectively. The average charging time for C40 was measured as $26.8{\pm}4.9$ seconds where the electrolyte and air flow-rates are 100 and $10{\mu}l/min$, respectively. Microbatteries showed the maximum voltage of 12 V (C40), the maximum power density of $110{\mu}W/cm^2$ (C40), and the maximum power capacity of $2.1{\mu}Ah/cm^2$ (C40). We also proposed a tapered-channel to remove the reaction gas from the cell chamber using a surface tension effect. The present microbatteries are applicable to high-voltage portable power devices.

• Current Applied Physics
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• v.18 no.11
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• pp.1345-1351
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• 2018

To allow stable cycling of layered nickel-rich cathode material at high voltage, silyl-functionalized dimethoxydimethylsilane is proposed as a multi-functional additive. In contrast to typical functional additive, dimethoxydimethylsilane does not make artificial cathode-electrolyte interfaces by electrochemical oxidation because it is quite stable under anodic polarization. We find that dimethoxydimethylsilane mainly focuses on scavenging nucleophilic fluoride species that can be produced by electrolyte decomposition during cycling, leading to improving interfacial stability of both nickel-rich cathode and graphite anode. As a result, the cell cycled with dimethoxydimethylsilane-controlled electrolyte exhibits 65.7% of retention after 100 cycle, which is identified by systematic spectroscopic analyses for the cycled cell.

• Journal of Information Processing Systems
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• v.6 no.1
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• pp.53-66
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• 2010

The energy efficiency is a key design issue to improve the lifetime of the underwater sensor networks (UWSN) consisting of sensor nodes equipped with a small battery of limited energy resource. In this paper, we apply a hexagon tessellation with an ideal cell size to deploy the underwater sensor nodes for two-dimensional UWSN. Upon this setting, we propose an enhanced hybrid transmission method that forwards data packets in a mixed transmission way based on location dependent direct transmitting or uniform multi-hop forwarding. In order to select direct transmitting or uniform multi-hop forwarding, the proposed method applies the threshold annulus that is defined as the distance between the cluster head node and the base station (BS). Our simulation results show that the proposed method enhances the energy efficiency compared with the existing multi-hop forwarding methods and hybrid transmission methods