A secondary on-board network battery for a secondary on-board network that is redundant to a primary on-board network of a motor vehicle, includes: a battery cell composite for providing electrical energy; a first connection for electrically connecting the secondary on-board network battery to at least one secondary on-board network component; a second connection for electrically connecting the secondary on-board network battery to the primary on-board network; a first switching device between the first connection and a connection point that is electrically connected to the battery cell composite; a second switching device between the second connection and the connection point, and a control unit configured to provide a conducting state for both switching devices for supplying the at least one secondary on-board network component from the primary on-board network, and for providing a locking state for the second switching device for keeping an overload on the primary on-board network side away.