A method for detecting an actual capacity of a battery using a characteristic curve field, the method comprising the steps of: determining at the beginning of a charging process an initial voltage (UL Beginn) of the battery, a charging rate and a temperature of the battery, by comparison of the charging rate and the temperature with data contained in the characteristic curve field, selecting a characteristic curve and determining an initial state of the battery, measuring at the end of the charging process a final voltage (UL Mess) and the charging current of the battery, comparing the final voltage (UL Mess) with an expected voltage (UL Erwartet) expected at the end of the charging process based on the selected characteristic curve and taking into consideration the magnitude of charging current input, and when the final voltage (UL Mess) is greater than the expected voltage (UL Erwartet) expected at the end of the charging process based on the selected characteristic curve, concluding that the actual capacity of the battery is smaller than the removable capacity assumed at the beginning of the charging process, determining at the beginning of a discharge process the initial voltage (UE Beginn) of the battery, a discharge rate and a temperature of the battery, by comparison of the discharge rate and temperature with data.contained in the characteristic curve field, selecting a characteristic curve and determining the initial state of the battery, measuring at the end of the discharge process the final voltage (UE Mess) of the battery, comparing the final voltage (UE Mess) with an expected voltage (UE Erwartet) expected at the end of the discharge process based on the selected characteristic curve, and when the final voltage (UE Mess) is smaller than the expected voltage (UE Erwartet) expected at the end of the discharge process based on the selected characteristic curve, concluding that the actual capacity of the battery is smaller than the removable capacity assumed at the beginning of the discharge process, and taking equally into account the results of the charging process and the results of the discharge process for determining the actual capacity of the battery. determining at the beginning of a charging process an initial voltage (UL Beginn) of the battery, a charging rate and a temperature of the battery, by comparison of the charging rate and the temperature with data contained in the characteristic curve field, selecting a characteristic curve and determining an initial state of the battery, measuring at the end of the charging process a final voltage (UL Mess) and the charging current of the battery, comparing the final voltage (UL Mess) with an expected voltage (UL Erwartet) expected at the end of the charging process based on the selected characteristic curve and taking into consideration the magnitude of charging current input, and when the final voltage (UL Mess) is greater than the expected voltage (UL Erwartet) expected at the end of the charging process based on the selected characteristic curve, concluding that the actual capacity of the battery is smaller than the removable capacity assumed at the beginning of the charging process, determining at the beginning of a discharge process the initial voltage (UE Beginn) of the battery, a discharge rate and a temperature of the battery, by comparison of the discharge rate and temperature with data.contained in the characteristic curve field, selecting a characteristic curve and determining the initial state of the battery, measuring at the end of the discharge process the final voltage (UE Mess) of the battery, comparing the final voltage (UE Mess) with an expected voltage (UE Erwartet) expected at the end of the discharge process based on the selected characteristic curve, and when the final voltage (UE Mess) is smaller than the expected voltage (UE Erwartet) expected at the end of the discharge process based on the selected characteristic curve, concluding that the actual capacity of the battery is smaller than the removable capacity assumed at the beginning of the discharge process, and taking equally into account the results of the charging process and the results of the discharge process for determining the actual capacity of the battery.