A contract was awarded to the Virginia Power Electronics Center to compare two battery discharger topologies for use on the Earth Observing System. The following report is the result of the optimal design, build and test of Voltage-Fed, Push-Pull Autotransformer battery discharger topology. The main thrust of this document is to achieve an optimal efficiency. The list of available parts is restricted to only those that are approved. Derating guidelines restrict the choice of power stage semiconductors in a manner that degrades efficiency so efficiency gains are sought by optimization of the power stage magnetics. A second goal of the design is to achieve optimal small and large signal performance. / Master of Science

Indiana University-Purdue University Indianapolis (IUPUI) / There is a strong urge for advanced diagnosis method, especially in high power battery packs and high energy density cell design applications, such as electric vehicle (EV) and hybrid electric vehicle segment, due to safety concerns. Accurate and robust diagnosis methods are required in order to optimize battery charge utilization and improve EV range. Battery faults cause significant model parameter variation affecting battery internal states and output. This work is focused on developing diagnosis method to reliably detect various faults inside lithium-ion cell using electrochemical model based observer and fuzzy logic algorithm, which is implementable in real-time. The internal states and outputs from battery plant model were compared against those from the electrochemical model based observer to generate the residuals. These residuals and states were further used in a fuzzy logic based residual evaluation algorithm in order to detect the battery faults. Simulation results show that the proposed methodology is able to detect various fault types including overcharge, over-discharge and aged battery quickly and reliably, thus providing an effective and accurate way of diagnosing li-ion battery faults.