Algorithm for Charging a Supercapacitor Energy Storage System

This paper presents a fast charging algorithm for battery bank made of connected in series supercapacitor cells. This algorithm allows simultaneously charging of all sells up to preliminary set up maximum voltage. Considering the tolerance in the capacitance of each cell and the fact that they are connected in series, we know that when the charging current is equal for all cells, the voltage across each cell will increase with different rate. In the presented algorithm, the charging current for each cell is different. The voltages across cells increase simultaneously. The fast charging time is a function of the capacitance and the current. Considering some limitations, we propose analytical equations for calculating the fast charging time as well as the required charging current for each cell. These limitations are in close connection to the varying capacitance of each cell as well as other parameters, described in the text below. The proposed algorithm is verified by a simulation model, representing four connected in series supercapacitor cells. Of course, the algorithm could also be applied to more than four cells. The presented results are obtained by using an LTSpice simulation software.