A method is disclosed to supply power to one or more battery-backup assemblies. The method supplies a first controller, a second controller, a first battery-backup assembly, and a second battery-backup assembly. The method further supplies a power bus interconnected to the first controller, the second controller, the first battery-backup assembly, and the second battery-backup assembly, and a first power supply and a second power supply interconnected with the power bus. The method provides power to the first controller and to the second controller and to the first battery-backup assembly over a first period of time, and provides power to the first controller and to the second controller and to the second battery-backup assembly over a second period of time, where the first period of time differs from the second period of time.