Operating method for a dual-voltage battery for a vehicle • comprising a plurality of battery cell blocks (A1, A2, A3, C, D) and • comprising battery electronics having a plurality of power switching elements (P0+, P1+, P2+, P3+, P2-, P3-, S1, S2, S3) for selectively connecting individual battery cell blocks (A1, A2, A3, C, D) in parallel and/or in series, wherein a first battery cell block and at least one further battery cell block (A2, A3) of a group (2, 3) of battery cell blocks (A1, A2, A3) • are connected in parallel in a first connection arrangement in order to provide a first voltage between a first terminal point and a ground terminal and • are connected in series in a second connection arrangement in order to provide a second voltage between a second terminal point and the ground terminal, • wherein at least one of the power switching elements (P0+, P1+, P2+, P3+, P2-, P3-, S1, S2, S3) as parallel connection switch (P1+, P...) and one of the power switching elements (P0+, P1+, P2+, P3+, P2-, P3-, S1, S2, S3) as series connection switch is associated with each battery cell block (A1, A2, A3) of the group (2, 3) of battery cell blocks (A1, A2, A3) in order to establish the parallel and/or series connection and wherein, in the first connection arrangement, the parallel connection switches (P1+, P2+, P3+, P2-, P3-) of all the battery cell blocks (A1, A2, A3) of the group (2, 3) of battery cell blocks (A1, A2, A3) are put into a closed position and the series connection switches (S1, S2, S3) of all the battery blocks (A1, A2, A3) of the group (2, 3) of battery cell blocks (A1, A2, A3) are put into an open position, wherein, in the first connection arrangement, at least one third battery cell block (C, D) can be connected in parallel with the group (2, 3) of battery cell blocks (A1, A2, A3), in the second connection arrangement, in which • by closing the series connection switches (S1, S2, S3) of all the battery cell blocks (A1, A2, A3) of the group (2, 3) of battery cell blocks (A1, A2, A3) and • by opening the parallel connection switches (P2+, P3+, P2-, P3-) of the further battery blocks (A2, A3) of the group (2, 3) of battery cell blocks (A1, A2, A3), the battery cell blocks (A1, A2, A3) of the group (2, 3) of battery cell blocks (A1, A2, A3) are connected in series in order to provide a second voltage, characterized in that, in the second connection arrangement, the parallel connection switch (P1+) of the first battery cell block is put selectively into a closed position or into an open position depending on an operating state of the vehicle, wherein, in the closed position of the parallel connection switch (P1+) of the first battery cell block, the first battery cell block of the group (2, 3) of battery cell blocks (A1, A2) can be connected in parallel with the at least one third battery cell block (C, D) in order to increase the capacity of the at least one third battery block (B, C) designed to provide the first voltage and in order to stabilize the energy supply at the first voltage. • comprising a plurality of battery cell blocks (A1, A2, A3, C, D) and • comprising battery electronics having a plurality of power switching elements (P0+, P1+, P2+, P3+, P2-, P3-, S1, S2, S3) for selectively connecting individual battery cell blocks (A1, A2, A3, C, D) in parallel and/or in series, • are connected in parallel in a first connection arrangement in order to provide a first voltage between a first terminal point and a ground terminal and • are connected in series in a second connection arrangement in order to provide a second voltage between a second terminal point and the ground terminal, • wherein at least one of the power switching elements (P0+, P1+, P2+, P3+, P2-, P3-, S1, S2, S3) as parallel connection switch (P1+, P...) and one of the power switching elements (P0+, P1+, P2+, P3+, P2-, P3-, S1, S2, S3) as series connection switch is associated with each battery cell block (A1, A2, A3) of the group (2, 3) of battery cell blocks (A1, A2, A3) in order to establish the parallel and/or series connection and • by closing the series connection switches (S1, S2, S3) of all the battery cell blocks (A1, A2, A3) of the group (2, 3) of battery cell blocks (A1, A2, A3) and • by opening the parallel connection switches (P2+, P3+, P2-, P3-) of the further battery blocks (A2, A3) of the group (2, 3) of battery cell blocks (A1, A2, A3),