Application of battery-ultracapacitor hybrid system in the hybrid electric vehicles

The main factors which include low charge/discharge efficiency of high current, low power density and poor low-temperature performance lead to the unsatisfactory situation for hybrid electric vehicles (HEVs), which involves the inadequate braking-energy recovery and short battery lifetime and limitation of working environment. To make up the performance of single battery, a battery and ultracapacitor (UC) hybrid system is used to give full play to the energy of the battery and power of the UC. This paper aims to put forward the design method of a battery-UC hybrid system from the perspective of the vehicle requirements and parameter matching. The experiment indicates that the hybrid power system has improved the efficiency of braking-energy recovery and has decreased the demanding power of battery markedly, thus prolonged the battery lifetime. Meanwhile, the UC's high low-temperature performance has improved the low-temperature performance of integrated power system. © 2013 Springer-Verlag.