Management of Supercapacitor Battery Charging

The main goal during charging a battery made of supercapacitors connected in series is reaching the rated voltages across all cells at the end of the charging process. The voltage imbalance is due to the tolerance in the nominal capacitance of the cells. The voltage equalization could be done by active and passive balancing methods. This work proposes active equalizing method with increasing charging current of the cell higher capacitance. For adding additional charging current to each cell, individual converters are used. The values of the additional charging currents have been obtained.

1. Introduction

There are many methods and algorithms allowing charging and voltage equalization for connected in series cells [1], [2]. Active and passive voltage equalizations are mainly used techniques. The active methods use electronic converters for transferring the excess energy between the cells. This energy could be distributed to some particular cell or to all cell simultaneously. For achieving higher coefficient of performance (KOP), synchronous converters are used [3], [4], [5], [6]. Choosing the right active balancing algorithm depends on the system application. There are requirements for minimum energy transfer or minimum power of the converters or minimum charging time or achieving equal voltages across the cells during the whole charging period and so on. What could be the power of the converters and what kind of algorithm we need depend on the required charging time. Some algorithms are inapplicable for fast charging. Transferring a minimum energy have difficulties in other algorithms if they make possible the voltage across all sells equal during the charging period.