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.