Evaluation of high power energy storage devices for use in compact pulsed power systems

摘要

The desire and need to field more compact pulsed power systems continues to grow with each passing day for use in many different applications. In the past, many pulsed power systems have been developed which use rechargeable batteries for the source of their prime power. In the time since the development of most of those systems, the demand for portable electronics and the growing desire to field hybrid electric vehicles has provided researchers with the resources needed to drastically improve the lifetime, safety, energy density, and power density of rechargeable batteries to technology levels only previously dreamed of. Improvements in these properties enable the development of prime power sources for pulsed power systems that are much more efficient and compact than those previously implemented. In these applications, where size is critical, the batteries are required to source currents at rates much higher than they are designed for in a high frequency, pulsed mode of operation. It is unclear how this extreme mode of operation impacts the size of the prime power system as well as how the capacity of the batteries will degrade compared to when they are discharged at their rated current. To gain a better understanding of the impact, the University of Texas at Arlington (UTA) is conducting experiments in which high power cells are pulsed discharged at an elevated rate. In the experiments presented here, a 3 Ah, lithium-ion battery has been discharged at a 100C rate, 300 A, using a switching frequency of 10 kHz and 50% duty cycle. The cell is periodically cycled at its rated current and the capacity fade and impedance variations are being evaluated and compared against a second identical cell which is being cycled under rated conditions. The test conditions, results collected thus far, and an analysis of how new technologies improves the size and efficiency of the prime power source will be presented. The results obtained are used to develop the model for the cell - hich shows the change in ESR and capacity as the cycle continues.