Method for controlling an electrical system of an electrically drivable motor vehicle, wherein the electrical system comprises at least one lead-acid battery and at least one lithium battery which can be electrically coupled to one another via a coupling device, wherein a first battery monitoring module is assigned to the at least one lead-acid battery and a second battery monitoring module is assigned to the at least one lithium battery, comprising the following steps: a) determining a lower threshold value and a first upper threshold value (USW, OSW1) for a state of charge of the lithium battery (step 100); b) determining a second upper threshold value above the first upper threshold value (step 110); c) during driving operation of the motor vehicle: adjusting a state of charge of the lithium battery between the lower threshold value and the second upper threshold value for the state of charge of the lithium battery (step 150); and d) when the motor vehicle is switched off: d1) determining the state of charge of the lithium battery (step 160); d2) if the state of charge of the lithium battery is greater than the first upper threshold value: lowering the state of charge of the lithium battery to the first upper threshold value (step 170, step 180, step 190), characterised in that a state of charge between 10 and 25% of the total capacity of the lithium battery is used as the lower threshold value for the lithium battery, a state of charge between 70 and 90% of the total capacity of the lithium battery is used as the first upper threshold value, and a state of charge between 80 and 100% of the total capacity of the lithium battery is used as the second upper threshold value. wherein a first battery monitoring module is assigned to the at least one lead-acid battery and a second battery monitoring module is assigned to the at least one lithium battery, comprising the following steps: a) determining a lower threshold value and a first upper threshold value (USW, OSW1) for a state of charge of the lithium battery (step 100); b) determining a second upper threshold value above the first upper threshold value (step 110); c) during driving operation of the motor vehicle: adjusting a state of charge of the lithium battery between the lower threshold value and the second upper threshold value for the state of charge of the lithium battery (step 150); and d) when the motor vehicle is switched off: d1) determining the state of charge of the lithium battery (step 160); d2) if the state of charge of the lithium battery is greater than the first upper threshold value: lowering the state of charge of the lithium battery to the first upper threshold value (step 170, step 180, step 190), a) determining a lower threshold value and a first upper threshold value (USW, OSW1) for a state of charge of the lithium battery (step 100); b) determining a second upper threshold value above the first upper threshold value (step 110); c) during driving operation of the motor vehicle: adjusting a state of charge of the lithium battery between the lower threshold value and the second upper threshold value for the state of charge of the lithium battery (step 150); and d) when the motor vehicle is switched off: d1) determining the state of charge of the lithium battery (step 160); d2) if the state of charge of the lithium battery is greater than the first upper threshold value: lowering the state of charge of the lithium battery to the first upper threshold value (step 170, step 180, step 190), d1) determining the state of charge of the lithium battery (step 160); d2) if the state of charge of the lithium battery is greater than the first upper threshold value: lowering the state of charge of the lithium battery to the first upper threshold value (step 170, step 180, step 190), characterised in that a state of charge between 10 and 25% of the total capacity of the lithium battery is used as the lower threshold value for the lithium battery, a state of charge between 70 and 90% of the total capacity of the lithium battery is used as the first upper threshold value, and a state of charge between 80 and 100% of the total capacity of the lithium battery is used as the second upper threshold value.