Method for controlling an energy storage device of a mild-hybrid-motor vehicle, wherein the energy storage device has a total capacity, comprising the following steps: a) by a state-of-charge control device of the energy storage device a state-of-charge of the energy storage device is set between an upper threshold (oSW) and a lower threshold (uSW) for a target state-of-charge range of the energy storage device, b) during at least one journey at least one charging process and one discharging process are monitored with reference to energy quantities exchanged with the energy storage device, and from the latter energy quantities to be expected for future charging and discharging processes are determined with a predeterminable probability, wherein the predeterminable probability is set in such a way that the target state-of-charge range is to be set such that the state-of-charge is outside the target state-of-charge range only in less than 10% of a predeterminable time period, and c) based on the determinations of step b) the upper threshold (oSW) and the lower threshold (uSW) for the target state-of-charge range of the energy storage device are determined, in the determination in step c) an upper, unusable charging range of the energy storage device and a lower, unusable charging range of the energy storage device and further an upper, unusable derating range and a lower, unusable derating range of the energy storage device are taken into account, wherein the derating range differs from the unusable range in that the derating range can be used in principle, but its use should be avoided as far as possible, since an output power of the energy storage device is reduced in the derating range, wherein in step c) the upper threshold (oSW) for the target state-of-charge range is determined as follows: upper threshold oSW = total capacity − upper, unusable charging range 14 − expected amount of energy for charging processes according to step b) and in step c) the lower threshold (uSW) for the target state-of-charge range is determined as follows: lower threshold uSW = lower, unusable charging range 16 + expected amount of energy for discharging processes accroding to step b). a) by a state-of-charge control device of the energy storage device a state-of-charge of the energy storage device is set between an upper threshold (oSW) and a lower threshold (uSW) for a target state-of-charge range of the energy storage device, b) during at least one journey at least one charging process and one discharging process are monitored with reference to energy quantities exchanged with the energy storage device, and from the latter energy quantities to be expected for future charging and discharging processes are determined with a predeterminable probability, wherein the predeterminable probability is set in such a way that the target state-of-charge range is to be set such that the state-of-charge is outside the target state-of-charge range only in less than 10% of a predeterminable time period, and c) based on the determinations of step b) the upper threshold (oSW) and the lower threshold (uSW) for the target state-of-charge range of the energy storage device are determined, in the determination in step c) an upper, unusable charging range of the energy storage device and a lower, unusable charging range of the energy storage device and further an upper, unusable derating range and a lower, unusable derating range of the energy storage device are taken into account, wherein the derating range differs from the unusable range in that the derating range can be used in principle, but its use should be avoided as far as possible, since an output power of the energy storage device is reduced in the derating range, wherein in step c) the upper threshold (oSW) for the target state-of-charge range is determined as follows: upper threshold oSW = total capacity − upper, unusable charging range 14 − expected amount of energy for charging processes according to step b) and in step c) the lower threshold (uSW) for the target state-of-charge range is determined as follows: lower threshold uSW = lower, unusable charging range 16 + expected amount of energy for discharging processes accroding to step b).