An extensive test has been conducted on a lithium-ion (Li-ion) cell under a variety of cycling conditions in order to evaluate factors that affect its cycle-life. The study is performed on a 900-mAh wound prismatic cell with contains a LiCoO2 positive electrode (cathode) and a synthetic graphite negative electrode (anode). Cycle-life is greatly influenced by the charge conditions, but is relatively insensitive to the discharge conditions. High charge cut-off voltages and a long float-charge period at 4.2 V or above have the most severe effects on cycle-life. Another damaging condition is high charge rates above the 1C rate, but reduction in the depth-of-discharge does not improve the cycle-life unlike the situation with other rechargeable batteries such as alkaline and lead-acid batteries. The dependence of the degradation rate on the charge voltage and the period of high charge voltage suggests that an electrochemical oxidation may be the cause.