Abstract: A system for controlling multiple energy storage devices in an uninterruptible power supply (UPS) system is provided. In one embodiment of the invention, the system generally includes a charger coupled to a direct current (DC) bus of the UPS system, and two or more energy storage circuits, each of which includes a power regulator coupled to the charger and coupled to the DC bus, at least one energy storage device coupled to the power regulator, and a processor coupled to the power regulator for controlling the charge and discharge of the at least one energy storage device. In another embodiment of the invention, digital communication between two or more controllers is accomplished over the DC bus through use of the Control Area Network (CAN) protocol.