Lithium-ion batteries are more commonly used today in a variety of applications from portable power to automotive and stationary energy storage. Due to the high cost of lithium-ion batteries and the fact that these batteries can perform really well even after 20% capacity loss, the batteries used in automotive applications are being considered for reuse in stationary energy storage installations. However, it is well known that although these types of second use installations have been initiated, very little has been understood regarding any changes that may occur with respect to the safety of these once-used or aged cells and batteries. The current study included studying single cells as well as modules to understand the cycle life trends as well as safety trends. Under cycle life testing of the cells and modules, two voltage ranges were studied and a set of cells were also subjected to HEV profiles at three different temperatures. Safety tests (overcharge and external short) were carried out on fresh and cycled cells and modules. Destructive physical examination with SEM and EDS analysis provided more insight into the physical and chemical changes that occur inside the cells under test. The results of this extensive study will be provided in this presentation.