Direct current energy storage system based on echelon utilization of retired batteries

The utility model discloses a DC energy storage system based on echelon utilization of decommissioned batteries, comprising a decommissioned battery module comprising a plurality of battery module units, each battery module unit being a decommissioned battery pack; the direct-current conversion module is used for being connected with a direct-current output bus end, the direct-current conversion module comprises a plurality of direct-current conversion channels which are arranged in parallel, and the input ends of the direct-current conversion channels correspond to the output ends of the battery module units one by one; the input end of the matrix switch module is connected with the output ends of the plurality of battery module units, and the output end of the matrix switch module is connected with the input ends of the plurality of direct current conversion modules; and the monitoring management module is used for controlling the matrix switch module to selectively open the number of the direct current con