State-of-Health (SOH) is a critical parameter for determining the safe operating area (SOA) of a battery cell and battery packs to avoid abuse and prevent failure and accidents. A set of experiments was performed to generate aging data on LiFePO4 batteries discharged with a specific load profile, with an emphasis on measuring changes in the 1 kHz – 0.1 Hz electrochemical impedance spectra (EIS). A parallel set of experiments was performed to identify a frequency range where the impedance response appears to be independent of the state of charge of the cell. Four 26650 cells were placed in a 4P1S array and discharged in parallel at 10 C (26 A) with the aforementioned load profile for a significant number of cycles to age the cells. Individual cell EIS measurements were taken, as well as measurements of the array as a whole. It is expected that deviations in the frequency-independent impedance response reflect SOH changes that may signal premature cell death. This work will discuss experimental results to date.