Abstract
Load variation shortens the lifetime of the fuel cell (FC) in an electric vehicle. The transient load should be buffered by an energy storage device, such as lithium ion battery. A new kind of lithium battery using Li4Ti5O12 (LTO) as anode can buffer the most. Since the LTO battery can suffer high rate current, it can be exploited to be a substitute for the battery with graphite anode (LC) in the fuel cell hybrid powertrain. However, since the LTO battery costs more, will it be a better choice? In this paper, dynamic cost evaluation models for the fuel cell hybrid powertrain is established. Comparisons are made between the powertrain structures of FC+LTO and FC+LC. By data collection, we find that the price of the LTO battery is probably three times than that of the ordinary Li-ion battery. However, the rated power for the FC can be reduced for the high power output capability of the LTO battery. So the FC costs in FC+LTO structure is less than that used in FC+LC structure. Then, reserved value is proposed to evaluate the life degradation of the fuel cell and the battery during road running. We propose possible dynamics by empirical formula to calculate the real-time life degradation of the powertrain. And the life degradation is transformed to reserved value. Simulation results of the reserved value show that by using LTO battery, the lifetime of the fuel cell hybrid powertrain extends to about 2 times than that of the original one. So the LTO battery may be a promising substitute used in the fuel cell hybrid powertrain.
KEYWORDS – Fuel cell, Li4Ti5O12 battery, hybrid powertrain, reserved value, dynamic cost analysis