According to at least one aspect embodiments herein provide a rack power system for providing DC power to equipment installed in a rack, comprising a first shelf containing a plurality of power supplies, each of the plurality of power supplies configured to receive AC power and to provide DC power to equipment installed in the rack, a second shelf containing a plurality of battery units, each of the plurality of battery units configured to provide DC power, and a controller coupled to the first shelf and the second shelf and configured to control each of the plurality of power supplies and configured to control each of the plurality of battery units.