Experimental characterization of hybrid power systems under pulse current loads

Lithium-ion batteries, ultracapacitors, and parallel combinations of these devices were characterized with respect to their ability to meet the power demands of pulsed loads. Data are presented in the form of Ragone plots that relate the impact of current amplitude and pulse duty to the specific power and energy storage capacities. Adding a 50 F ultracapacitor in parallel with the battery exhibited up to a 20.3% increase in energy capacity as compared to a continuous discharge of the battery alone. The peak current capacity of the hybrid system was limited to 10 A, to prevent exceeding the maximum safe current of 2.4 A for the battery alone. The hybrid systems also suffered less voltage droop during the pulse ‘on’ time when compared to the battery alone. However, when considered on a per mass basis, the energy and power densities were lower for the hybrids than for the battery alone.