Electric vehicle using a combination of ultracapacitors and zebra battery

Abstract

The Sodium Nickel-Chloride battery, commonly known as ZEBRA, has been used for an experimental electric vehicle. These batteries are cheaper than Li-ion cells, have a comparable specific energy (Wh/kg), but one important limitation is their poor specific power (W/kg). The main objective of this paper is to demonstrate experimentally that the combination of ZEBRA batteries and ultracapacitors can solve the lack of specific power, allowing an excellent performance in both, acceleration and regenerative braking in an EV (Electric Vehicle). The ultra capacitor system was connected to the ZEBRA battery and to the traction inverter through a Buck-Boost type DC-DC converter, which manages the energy flow with the help of DSP controllers. The vehicle uses a brushless dc motor with a nominal power of 32 kW, and a peak power of 53 kW. The control system measures and stores the following parameters: battery voltage, car speed to adjust the energy stored in the ultracapacitors, instantaneous currents in both terminals (battery and ultracapacitors), and present voltage of the ultracapacitor. The increase in range with ultracapacitors results in more than 16% in city tests, where the application of this type of vehicle is being oriented. The results also show that this alternative is cheaper than Li-ion powered electric cars.