A method/controller for operating a vehicle regenerative braking system by operating in a first braking mode, in which a generator braking torque of a generator is not zero and is equal to a first regenerative portion predefined for the first mode, and controlling the system out of the first mode into a second braking mode having a second regenerative portion, which is smaller than the first portion, so that brake fluid is pumped out of a storage volume of the system into at least one wheel brake cylinder and/or at least one brake circuit of the system via at least one brake fluid delivery mechanism; by activating the delivery mechanism via a setpoint delivery output variable, which is established/predefined for a setpoint brake pressure having a setpoint pressure rise which increases over time, so that an actual brake pressure having an actual pressure rise increase over time is built up.