A novel scheme for optimal paralleling of batteries and ultracapacitors

A hybrid power pack consisting of batteries and ultracapacitors has the advantage of combining high energy capability (batteries) with high power capability (ultracapacitor). This paper suggests a new scheme for combining batteries and ultracapacitors with new modes of operation. The scheme supports high speed dynamic cell voltage equalization of a series connected battery string and can transfer charge between batteries and ultracapacitors in addition to improving the specific power capabilities of a battery system (charge and discharge). A circuit topology is proposed and operation modes are defined. Efficiency is improved by better utilization of battery capacity and decreased stress on batteries. These lead to performance improvements and better utilization of ultracapacitors compared to other schemes in existence.