Control unit for a power supply device, wherein the power supply device has: - a battery store having at least one battery unit that has a startup time (tB) and a battery power, - a first energy conversion device that converts nonelectrical energy into electrical energy, - a connecting unit that is connected to the battery store and the first energy conversion device and that is configured such that a summed energy for the electrical energy of the first energy conversion device and of the battery store is deliverable at its output, wherein - the control unit receives an instantaneous output power (Po(to)) of the first energy conversion device; - the control unit receives a predicted power (Pf(t)) of the first energy conversion device for at least one future time; - the control unit is configured such that firstly the instantaneous output power (Po(to)) and secondly the predicted power (Pf(t)) are used to ascertain a required power (PBESS) at the future time, the required power (PBESS) is compared with a first threshold value and at least one battery unit is switched on if said threshold value is exceeded, characterized in that - the control unit is configured such that the instantaneous output power (Po(to)) is used to ascertain a computed output power (Pmin(t)) for the at least one future time, the computed output power (Pmin(t)) and the predicted power (Pf(t)) being used to ascertain the required power (PBESS) for the at least one future time, and - the control unit is configured such that the computed output power (Pmin(t)) is the difference between the instantaneous output power (Po(to)) as minuend and a safety reduction as subtrahend, the safety reduction being a product of a rise per unit time and the time difference between future time and present time. - a battery store having at least one battery unit that has a startup time (tB) and a battery power, - a first energy conversion device that converts nonelectrical energy into electrical energy, - a connecting unit that is connected to the battery store and the first energy conversion device and that is configured such that a summed energy for the electrical energy of the first energy conversion device and of the battery store is deliverable at its output, wherein - the control unit receives an instantaneous output power (Po(to)) of the first energy conversion device; - the control unit receives a predicted power (Pf(t)) of the first energy conversion device for at least one future time; - the control unit is configured such that firstly the instantaneous output power (Po(to)) and secondly the predicted power (Pf(t)) are used to ascertain a required power (PBESS) at the future time, - the control unit is configured such that the instantaneous output power (Po(to)) is used to ascertain a computed output power (Pmin(t)) for the at least one future time, the computed output power (Pmin(t)) and the predicted power (Pf(t)) being used to ascertain the required power (PBESS) for the at least one future time, and - the control unit is configured such that the computed output power (Pmin(t)) is the difference between the instantaneous output power (Po(to)) as minuend and a safety reduction as subtrahend,