Sensor to detect a mechanical stress on the battery pack

1. A method for controlling a system having a power tool, at least one battery having at least one energy storage cell, at least one acceleration sensor for detecting at least one acceleration value in an X, Y and Z direction, at least one piezoelectric sensor, a controller, signal transmitter and a measurer for measuring a voltage, the method comprising the steps of:

determining vibration values acting upon the system by detecting acceleration values within a predetermined range;

determining a free-fall state of the system by detecting an acceleration value in the X, Y and Z direction being equal to a predetermined range;

determining an impact of the system by detecting at least one acceleration value in the X, Y and Z direction exceeding a first predetermined threshold value;

determining a traveling distance between the detecting the acceleration value in the X, Y and Z direction being equal to the predetermined range and the detecting the at least one acceleration value in the X, Y and Z direction exceeding the first predetermined threshold value;

determining a shock value via the at least one piezoelectric sensor or the at least one acceleration sensor;

detecting a first and second voltage values of the at least one energy storage cell via the measurer for measuring the voltage; and

sending out a first signal via the signal transmitter if the acceleration values within the predetermined range for determining vibrations exceed the first predetermined threshold value for a first predetermined time period, a determined drop height exceeds a further predetermined threshold value, the determined shock value for determining a shock exceeds a yet further predetermined threshold value or a difference value between the first and second voltage values exceeds a still yet further predetermined threshold value.

2. The method as recited in claim 1 further comprising sending out a second signal via the signal transmitter if the acceleration values within the predetermined range for determining vibrations exceed a second predetermined threshold value for a second predetermined time period, the determined drop height exceeds a second further predetermined threshold value, the determined shock value for determining a shock exceeds a second yet further predetermined threshold value or a difference value between the first and second voltage values exceeds a second still yet further predetermined threshold value.

3. The method as recited in claim 2 further comprising sending out a third signal via the signal transmitter if the acceleration values within the predetermined range for determining vibrations exceed a third predetermined threshold value for a third predetermined time period, the determined drop height exceeds a third further predetermined threshold value, the determined shock value for determining a shock exceeds a third yet further predetermined threshold value or a difference value between the first and second voltage values exceeds a third still yet further predetermined threshold value.

4. The method as recited in claim 3 further comprising sending out a fourth signal via the signal transmitter, if an occurrence of an event in which at least one acceleration value exceeds the first predetermined threshold value, exceeds a predetermined quantity during a fourth predetermined time period.

5. A system for carrying out the method as recited in claim 1 and comprising the power tool, the at least one battery, the at least one acceleration sensor, the controller, and an interface for an exchange of data between the at least one battery, the at least one piezoelectric sensor, the signal transmitter and the power tool, and the measurer.

6. The system as recited in claim 5 further comprising at least one temperature sensor for measuring a temperature inside the battery.