Abstract: A drive system may have at least one electric motor which can be fed via power electronics which can be connected via a DC circuit to a voltage source and an energy storage apparatus for buffering energy fed back from the electric motor. An energy storage apparatus for such a drive system may include at least one electrical storage block, a bidirectional DC/DC converter for connecting the named DC voltage circuit to the internal voltage circuit of the storage block and a control unit for controlling the DC/DC converter. The control unit may include output and feed control means for controlling the DC/DC converter. The DC/DC converter, the storage block and the control unit may be combined into an energy storage unit having a common housing in which the named components are received and at whose outer side two connections are provided for connecting to the DC voltage circuit.