A sensor for position determination of a drive system comprising: a magnetic sensor adapted to determine the rotational position of a magnet linked to the drive system; at least one Hall sensor to determine rotational movement and direction of rotation of the magnet; a microcontroller unit for evaluating data of the magnetic sensor and of the Hall sensor; and a rechargeable battery connected to a power supply of the sensor and that represents an alternative power supply, wherein, on a failure of the power supply, the sensor is adapted only to supply the Hall sensor and the microcontroller unit with energy from the rechargeable battery when the Hall sensor does not detect any rotational movement of the magnet and to supply at least one further component of the sensor with energy from the rechargeable battery when the Hall sensor detects a rotational movement of the magnet.