Droop control as a well known approach is used as the basis of the power sharing among different paralleled voltage sources and battery energy storage systems (BESS). In order to extend the lifetime of BESS and avoid the overuse of a certain battery, the State of the Charge (SoC) of BESS should be balanced. This paper reviews and compares three different droop control methods in an islanded DC microgrid that are based on balancing the SoC of different BESS. All of the presented methods are compared together and the best one is selected. The feasibility of the selected method is verified through computer simulations in MATLAB/Simulink for a DC microgrid consisting of three BESS, PV (Photovoltaic) arrays and DC load.