In this paper, we consider the provision of primary frequency control by using battery energy storage systems (BESSs). In particular, we use a standard droop-based frequency control for a BESS where the control action (i.e. the BESS power output) consists in the contribution of two additive terms: the regulating power, proportional to the frequency deviations, and an offset term computed to manage the BESS State-of-Energy (SOE). In the context of such a control scheme, we propose a method to forecast the BESS energy for regulation needs and we show that the inclusion of such a forecast can increase the regulating power provision. Finally, we demonstrate the performance of the proposed approach by means of a real-scale experimental setup composed by a grid-connected 720 kVA/560 kWh BESS installed at the EPFL campus in Lausanne, Switzerland.