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Effects of High Frequency Discontinuous Current Cycling in Ultracapacitors

Mark Stevens
Ohio Northern University

An ultracapacitor (UC) is an electrochemical capacitor that has an unusually high energy density when compared to common capacitors. They have recently become of particular interest in automotive applications for hybrid vehicles and as supplementary storage for electric vehicles powered by batteries, fuel cells, solar cells, and hybrid electrical energy storage systems. Most applications of ultracapacitors require a way to make output voltage consistent as it varies with the state of charge. In this situation, the DC/DC buck converter is commonly used. The buck converter, however, uses a discontinuous current to regulate voltage. Internally, the UC contains a non-ideality called the Equivalent Series Resistance (ESR). We aim to study the effects of this discontinuous current cycle on the overall lifespan of the UC using the ESR and capacitance as indicators. Testing design and setup as well as initial results will be presented.

ONU Student Research Colloquium