Battery system with a voltage equalizing circuit

1. A battery system comprising:

a battery cell; and

a voltage balancing circuit for balancing a voltage at the battery cell;

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 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.

2. The battery system as claimed in claim 1 , wherein the measuring arrangement is electrically connected on the signal-input side to the negative power connection terminal of the battery cell and is configured to detect a second voltage potential at the negative power connection terminal.

3. The battery system as claimed in claim 1 , wherein the analog-to-digital converter is electrically connected to the negative power connection terminal of the battery cell by a second signal input and is configured to:

form a second digital voltage potential value from the second voltage potential; and

form the measurement voltage from the first and the second digital voltage potential value.

4. 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.

5. 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.