A Practical Supercapacitor Model for Power Management in Wireless Sensor Nodes

In this paper, a new practical method is presented to estimate supercapacitor state for wireless sensor nodes. The self-discharge process of supercapacitor, as an energy storage device in sensor nodes, is usually considered as the main factor that needs to be taken into account for power management. Recent studies have demonstrated that a supercapacitor charge-redistribution process may also have significant impact on power management. To consider charge redistribution in power management of a real-time system, a practical method is presented to estimate the state of a supercapacitor. The accuracy of the method is validated by experiments. The impact of time step on the proposed model is also investigated. The results indicate that the proposed model can achieve good accuracy with relatively large time step. Moreover, the model is easy to implement, and has low memory usage and computational cost for practical applications in a real-time system. Based on the practical model, estimations of charge and energy transferred during the redistribution process are presented, which provide important information toward developing energy aware algorithms in wireless sensor networks.