For reliable operation of an islanded microgrid, at least one of its distributed resources should assume the responsibility of forming the off-grid power system. This responsibility is usually assumed by energy storage systems based on their capability of compensating the unbalance between generation and consumption. However, the storage units lose this capability when they reach the maximum and minimum limits of charge. Under these conditions, the regulation of the power grid may be assumed by another unit with enough capability or the power balance should be adjusted coordinately. This paper proposes a coordination architecture for islanded ac microgrids, which considers the appropriate charge profiles for battery-based energy storage systems. The architecture is based on distributed decision-making mechanisms, which use only local measurements for determining the operation mode of each unit independently. The coordination relies on a bus-signaling method, which enables the distributed units to have a global perception about the operation of the microgrid, without any communication infrastructure. The proposed architecture includes cooperative operation between distributed energy storage systems for achieving the equalization of the states of charge. Experimental results in a lab-scale microgrid with network configuration validate the proposed strategy under different operational conditions.