The Idaho National Laboratory (INL) tested six Saft America HP-12 (Generation 2000), 12-Ah lithium ion cells to evaluate cycle life performance as a power assist vehicle battery. The cells were tested to investigate the effects of temperature on capacity and power fade. Test results showed that five of the six cells were able to meet the power assist power and energy goals at the beginning of test and after 300,000 cycles using a battery size factor (BSF) of 44.3 cells. The initial static capacity tests showed that the capacities of the cells were stable for three discharges and had an average of 16.4Ah. All the cells met the self-discharge goal, but failed to meet the cold cranking goal. As is typical for lithium ion cells, both power and capacity decreased during the low-temperature thermal performance test and increased during the high-temperature thermal performance test. Capacity faded as expected over the course of 300,000 life cycles and showed a weak inverse relationship to increasing temperature. Power fade was mostly a result of cycling while temperature had a minor effect compared to cycle life testing. Consequently, temperature had very little effect on capacity and power fade for the proprietary G4 chemistry.