MODELING AND APPLICATION STUDIES OF AN ELECTROCHEMICAL HYBRID SYSTEM

A first principle based mathematical model is presented to simulate the performance of a lithium-ion battery/electrochemical capacitor hybrid system. The advantages of the hybrid system over the battery system are discussed for pulse type of loads. The hybrid system predicted better utilization of the battery operated under high frequencies and low duty ratio pulse loads. Simulated specific energy and power relationships (Ragone plots) are also presented to identify regimes where the hybrid systems performed better than the battery system on a unit mass basis. The model was validated by comparing the simulations to the experimental data obtained from a Sony US 18650 lithium-ion battery/Maxwell PC100F electrochemical capacitor network hybrid system. Finally a case study comparing the response of the battery and a hybrid system to two different high power pulse profiles encountered in real time applications is presented. Simulation results indicate that hybrid systems exhibited superior performance over the battery system for pulse power profiles with sufficient relaxation times.