Lithium-Ion Performance Testing and AC Impedance Characterization

The performance and life of lithium-ion batteries is highly dependent on factors such as temperature, charge/ discharge rate, depth-of-discharge (DOD), charge cut-off voltage, and battery design. The purpose of this on-going investigation is to characterize the state-of-the-art in lithium-ion battery performance and life as a function of some of these factors. Cycle life data on 18650 cells as well as a four cell series connected 20 Ahr lithium-ion battery (16.4 volt) is presented. External cell temperatures as a function of discharge rate and location for 20 Ahr lithium-ion cell are given. Preliminary ac impedance results for the 20 Ahr cell are also given.