High efficient battery backup system for lift trucks using interleaved-converter and increased EDLC voltage range

To obtain highest efficiency in electric vehicles and to increase the lifetime of the traction battery, a battery backup system is mandatory. In this paper, the investigation of a system for an electric lift truck propulsion system consisting of Electric Double Layer Capacitors and a DC/DC-converter, is presented. Primarily, the super capacitor voltage range is analyzed comparing super capacitor, inductor and MOSFET rating as well as prospected losses. The most suggestive range is determined. Accordingly, a high efficient interleaved DC/DC-converter is designed and its benefits against single phase converters are specified. The proposed configuration is analyzed and built up in the laboratory. Measurements confirm the theoretical considerations and show the advantages of this addional backup system.