Supercapacitor Energy Delivery Capability During a Constant Power Discharge Process

This paper studies the supercapacitor energy delivery capability during a constant power discharge process, which refers to the amount of energy delivered by a supercapacitor when a constant power load is applied. Extensive constant power discharge experiments are conducted using three supercapacitor samples with different rated capacitances from different manufacturers. The relationship between the delivered energy and the discharge power is examined. In the upper bound case corresponding to a fully charged supercapacitor, the delivered energy increases when the discharge power decreases if the discharge power is above a certain threshold, i.e., Peukert's law applies. When the discharge power is below the threshold, this law does not apply anymore. In the lower bound case corresponding to a partially charged supercapacitor, the delivered energy peaks at a particular discharge power. These relationships are due to the combined effects of three aspects of supercapacitor physics: porous electrode structure, charge redistribution, and self-discharge. This paper also compares the bounds of the delivered energy and shows that the difference is significant.