Control strategy and lifetime optimization of Electrochemical Double-Layer Capacitors

Today, the most commonly used energy storage device in embedded systems is bat-teries. But unfortunately, batteries are associated with short lifetime. By introducing Electrochemical Double-Layer Capacitors (EDLCs) as an alternative power source, the lifetime of the backup energy source can be significantly increased. The lifetime is dependent on two predominant factors; temperature and volt-age. To evaluate the aging behavior of EDLCs, accelerated lifetime tests where per-formed. The measurements were carried out on capacitors from two different man-ufacturers (Cooper Industries and Maxwell Technologies). The results were then used for lifetime estimations. To accomplish an increased lifetime, a control system is suggested which mon-itors the capacitance and controls the applied voltage i.e. optimizing the amount of stored energy. A complete power back up system with EDLCs as power source and an associated control system, was built and simulated in Simulink. Furthermore, an electrical hardware prototype was implemented to create a proof-of-concept. It is found that the lifetime can be significantly increased when controlling the applied voltage, since the voltage can be held as low as possible at all time