IMPEDANCE EFFECTS OF RECHARGEABLE BATTERIES ON DIGITAL-COMMUNICATION DEVICES

Present (and future) wireless communications use (will use) digital electronics to bunch and pack more data into the available communications spectrum. This strategy requires an energy storage device capable of delivering large, pulsed currents which may approach 4A for 15msec once every 90msec. Emerging energy storage technologies, such as nickel-metal hydride and Li-ion cells, have enhanced energy densities but greater internal impedance when compared to the traditional nickel-cadmium cells. Experiments simulating battery discharge in a digital wireless communications application demonstrate the effects of internal impedance on the overall ability of the cells to meet digital device requirements. Results indicate that, currently, nickel-cadmium may be the best available technology for these digital applications.