Integration and Testing of a DC/DC Controlled Supercapacitor into an Electric Vehicle

The primary goal of this project was to demonstrate improved performance and equipment reliability in a Solectria Force electric vehicle associated with the installation of a Maxwell PowerCache ultracapacitor module and a Solectria prototype integrated controller. A supercapacitor provides a high efficiency energy storage unit that can provide short bursts of power and rapidly capture braking regenerative energy. These characteristics are consistent with the energy use associated with acceleration/deceleration in electric vehicles[2]. The test program included summer and winter testing on a suburban test course, acceleration testing on a flat roadway and dynamometer, an urban driving course, cold and warm temperature dynamometer testing on the FUDDS cycle, and dynamometer testing on the US EPA IM240 cycle. The supercapacitor efficiently responded to high power demands and effectively recovered regenerative energy, modulating peak battery current. The capacitor system allowed more total energy to be drawn from the batteries. Due to the inefficiency of energy transfer into and out of the capacitor through the DC/DC controller, range and performance improvements as compared to the control vehicle depended strongly on the driving cycle.