Abstract: A method and an apparatus for monitoring a low-pass filter, preferably a capacitor in a low-pass filter, a battery management system and a battery are provided. The apparatus includes a switch connected in series with a resistor, and a capacitor connected in parallel with the resistor. When the switch carries out a switching operation, the voltage changes within a very short time from a first to a second voltage value. A voltage detection device measures the voltage during switching and at at least one further point in time, 0.5 to 5 milliseconds later. Determining the speed at which the voltage changes from the first voltage value to the second voltage value makes it possible to determine whether the capacitor is functional and/or makes it possible to determine the resistance. Determining the internal resistance of a battery cell also makes it possible to determine the state of charge of a battery.

Abstract: An electromotor can be selectively actuated for operation in both rotational directions. In the condition of the electromotor not energized with current, respectively one rotational direction of the electromotor is blocked and one rotational direction remains movable in a free-running manner. The circuit includes first and second diodes forward-connected from ground to first and second motor terminals, a respective change-over switch connecting each motor terminal selectively to power or ground, and a free-run blocking switch interposed preferably between one of the motor terminals and its associated change-over switch.

Abstract: The invention relates to a circuit arrangement of an electromotor comprising two terminals, in which the electromotor can be actuated for operation for both rotational directions, and in which, in the condition of the electromotor not energized with current, respectively one rotational direction of the electromotor is blocked and one rotational direction remains movable.