Due to the increasing concern for energy efficient storage devices, extensive research is being done on the mechanisms which are involved in the battery degradation process. The electric battery loses capacity with use throughout its lifetime, decreasing the total amount of energy it can store and deliver. As the battery degrades, the internal resistance also increases resulting in a difficult extraction of the stored energy as well as the loss of part of this energy, during charging and discharging, in the form of heat. Optimality in electric vehicle energy management has been traditionally pursued from the perspective of efficient grid operation, but barely considering battery degradation in the process. The objective is to formulate a battery degradation model which will yield the degradation suffered by a battery as a function of its use, allowing both the comparison between different energy management strategies as well as including the model in linear optimization algorithms. A number of Li-ion battery cells experimentally subjected to different depth-of-discharges, currents and temperatures, were studied in order to identify the variables which categorize best, using self-organizing maps, the degradation suffered by the cells. A model is proposed which yields the rate of degradation of the battery as a function of both temperature and depth-of-discharge. This model is then linearized and used in an electric vehicle energy management optimization problem where the degradation suffered by the battery, due to a managed charge, is minimized as a function of the depth-of-discharge and the temperature. The results are compared with other charging methods.
Director: Álvaro Sánchez Miralles
Autor: Ismael J. Fernandez
Lugar: Aula de seminarios

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