This paper introduces a pseudo three-dimensional electrochemical-thermal coupled battery model for a cylindrical Lithium Iron Phosphate battery. The model comprises a pseudo two-dimensional electrochemical cell model coupled with three-dimensional lumped thermal model. The cell is disassembled to obtain the physical dimensions of the cell components. The thermal characteristics of the cell are studied during the discharge process over a range of temperatures and discharge rates. The validity of the numerical model is demonstrated experimentally via a 26650 cylindrical Lithium Iron Phosphate/graphite battery cylindrical cell.Instead of infrared thermal images, series of regression models are utilized to quantify the thermal behavior at various depth of discharge under various discharge rates. The results demonstrated that the battery cell performs differently at a lower ambient temperature and lower discharge rate where the exothermic reactions are milder.

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This paper presents an integrated state-of-charge (SOC) estimation model and active cell balancing of a 12-cell lithium iron phosphate (LiFePO4) battery power system. The strong tracking cubature extended Kalman filter (STCEKF) gave an accurate SOC prediction compared to other Kalman-based filter algorithms. The proposed groupwise balancing of the multiple SOC exhibited a higher balancing speed and lower balancing loss than other cell balancing designs. The experimental results demonstrated the robustness and performance of the battery when subjected to current load profile of an electric vehicle under varying ambient temperature.

The use of fuel cell technology as a backup power source for the uninterruptible power supply (UPS) requires quick response to sudden load change. However, slow dynamic behavior of a PEM fuel cell, compared to the typical power conditioner and load, limits the fuel cell rapid transient response to load change. To increase the fuel cell response to load change, the energy storage such as battery, micro turbine, photovoltaic and super-capacitors are conventionally installed in the system thus increasing in its size and cost. In this work, the PEM fuel cell transient behaviors in the cool-start, hot-start and load change were investigated by using in-house running control software and high precise oscilloscope. The effects of fuel cell structure (area of flow field, cell number and materials used in MEA) and operation conditions (pressure, temperature etc.) were also studied. The electrical response results from experimental curves indicate that the transient behavior of fuel cell stack is highly impacted by the fuel cell structure, operating conditions and the strategy of gas input into the fuel cell. The better understanding of the electrical response of PEM fuel cell would be helpful to the design of a fuel cell and its system with high efficiency and compact structure.

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