Integrating a battery energy storage system (BESS) with a large wind farm can smooth out the intermittent power from the wind farm. This paper focuses on development of a control strategy for optimal use of the BESS for this purpose. The paper considers a conventional feedback-based control scheme with revisions to incorporate the operating constraints of the BESS, such as state of charge limits, charge/discharge rate, and lifetime. The goal of the control is to have the BESS provide as much smoothing as possible so that the wind farm can be dispatched on an hourly basis based on the forecasted wind conditions. The effectiveness of this control strategy has been tested by using an actual wind farm data. Finally, it is shown that the control strategy is very important in determining the proper BESS size needed for this application.