Monitoring System for Testing the Performance of an Electric Vehicle Using Ultracapacitors

A monitoring system for an Electric Vehicle, which uses an ultracapacitor bank, has been implemented. The purpose of this system is to test the performance of the vehicle under different road conditions (city road and highway), with and without the ultracapacitors connected. One of the most important objectives of the work is to test the efficiency gain of the vehicle, and the current flow coming from the batteries in both cases, to allow the evaluation of the battery life change. These results will lead to conclusions about the overall economical and technical advantage of the use of ultracapacitors in combination with batteries in electric vehicles. The efficiency gain is being monitored at the ultracapacitor level, at the battery level, and at the vehicle level. Related with the design of the ultracapacitor system, this has been optimized in weight and size, by using a watercooled IGBT power converter, and an aluminum inductor with air core. The ratings of the ultracapacitor bank are: nominal voltage: 300 Vdc; nominal current: 200 Adc; capacitance: 20 Farads. The amount of energy stored allows having 40 kW of power during 20 seconds, which is enough to accelerate the vehicle with minimum help of the traction batteries. The vehicle uses a brushless dc motor with a nominal power of 32 kW, and a peak power of 53 kW. The control system, based on a DSP, measures and stores the following parameters: battery voltage, battery state-of-charge, car speed, instantaneous currents in both terminals (battery and ultracapacitor), and actual voltage of the ultracapacitor. Once the tests on the streets are finished, data will be analyzed and compared with previous results, with and without the ultracapacitors connected. The increase in range with ultracapacitors has been estimated in 16% in city tests, but the difference looks almost negligible in highway tests. However, tests are still under way. The car used for this experiment is a Chevrolet LUV truck, similar in shape and size to a Chevrolet S-10, which was converted to an electric vehicle at the Catholic University of Chile. Copyright 2002 EVS19