Battery system with a voltage equalizing circuit

A method for identifying a faulty state of a voltage balancing circuit comprising a balancing current path electrically connected between a positive power connection terminal and a negative power connection terminal of a battery cell, two resistors, and a balancing switch connected in series with the two resistors, and a measuring arrangement electrically connected on a signal-input side to an electrical connecting point between the two resistors and configured to detect a first voltage potential at the electrical connecting point, an analog-to-digital converter electrically connected to the electrical connecting point by a first signal input and configured to form a first digital voltage potential value from the first voltage potential, and a filter electrically connected between the electrical connecting point and the analog-to-digital converter and configured to suppress AC potential components in the first voltage potential, a controllable bypass switch electrically connected between the electrical connecting point and the analog-to-digital converter in parallel with the filter and configured to bypass the filter in a closed switching state, and a further filter electrically connected between the negative power connection terminal and the second signal input of the analog-to-digital converter, the method comprising:

• opening the balancing switch;
• detecting a first measurement voltage at the battery cell;
• closing the balancing switch;
• detecting a second measurement voltage at the battery cell;
• calculating a voltage difference between the first and the second measurement voltage;
• comparing the voltage difference to a prescribed voltage tolerance range;
• identifying a fault in the voltage balancing circuit or in the electrical connection to the battery cell if the voltage difference is outside of the prescribed voltage tolerance range;
• wherein detecting the second measurement voltage includes measuring the second measurement voltage when the bypass switch is closed;
• and
• measuring further voltages for checking of a possible fault caused by a deviating cutoff frequency of one of the two filters while the balancing switch is closed and the bypass switch is open.

An electrical drive arrangement comprising:

• an electric machine for electrical driving;
• a power output stage for operating the electric machine;
• a battery system for providing electrical energy for the electric machine, the battery system comprising:
• a battery cell;
• and
• a voltage balancing circuit for balancing a voltage at the one;
• wherein the voltage balancing circuit includes:
• a balancing current path electrically connected between a positive power connection terminal and a negative power connection terminal of the battery cell, two resistors, and a controllable balancing switch connected in series with the two resistors;
• and
• a measuring arrangement electrically connected on a signal-input side to an electrical connecting point between the two resistors and configured to detect a first voltage potential at the electrical connecting point;
• wherein the battery system is electrically connected to the power output stage by electrical connection terminals and to the electric machine by the power output stage;
• wherein the measuring arrangement comprises:
• an analog-to-digital converter electrically connected to the electrical connecting point by a first signal input and configured to form a first digital voltage potential value from the first voltage potential;
• a filter electrically connected between the electrical connecting point and the analog-to-digital converter and configured to suppress AC potential components in the first voltage potential;
• and
• a controllable bypass switch electrically connected between the electrical connecting point and the analog-to-digital converter in parallel with the filter and configured to bypass the filter in a closed switching state.