Method for determining the state of health of a rechargeable battery

1 . A method for open-loop and closed-loop control of a rechargeable battery for supplying a power tool with electrical energy, the rechargeable battery containing at least one energy storage cell, at least one temperature sensor, a current measurer, a voltage measurer and a rechargeable battery controller having at least one rechargeable battery storage, the method comprising the steps of:

adjusting the rechargeable battery from a first state of charge to a second state of charge;

creating a first current intensity value after a first predetermined time duration has elapsed, after a predetermined temperature value has been reached, after a predetermined current intensity value has been reached, or if the difference between a first and a second ascertained current intensity value reaches a predetermined threshold value;

ascertaining a first voltage value after the first current intensity value has been reached;

adjusting a second current intensity value after a second predetermined time duration has elapsed;

ascertaining a second voltage value after the second current intensity value has been reached; and

determining a first impedance value of the rechargeable battery from the quotient of the difference between the first and second current intensity values and the difference between the first and second voltage values.

2 . The method as recited in claim 1 wherein the first voltage value is ascertained after a third predetermined time duration has elapsed after the first current intensity value has been reached.

3 . A rechargeable battery for carrying out the method as recited in claim 1 , the rechargeable battery comprising: the at least one energy storage cell, the at least one temperature sensor, the current measurer, the voltage measurer and the rechargeable battery controller having the at least one rechargeable battery storage.

4 . A charger for carrying out the method as recited in claim 1 , the charger comprising: a charger controller having at least one charger storage.

5 . The method as recited in claim 1 wherein the power tool is a rechargeable battery-operated screwdriver.

6 . The method as recited in claim 1 wherein the step of adjusting the rechargeable battery from a first state of charge to a second state of charge is done via a charging process, the charging process including electrical energy passing from a charger to the rechargeable battery.

7 . The method as recited in claim 1 wherein the step of adjusting the rechargeable battery from a first state of charge to a second state of charge is done via a discharging process, the discharging process including electrical energy passing from the rechargeable battery to the power tool.

8 . The method as recited in claim 2 wherein the first predetermined time duration is between 5 and 10 seconds and the third predetermined time duration is between 1 and 5 seconds.

9 . The method as recited in claim 1 wherein the at least one energy storage cell includes at least three energy storage cells, the at least three energy storage cells being positioned in three rows, the temperature sensor being positioned between two of the three rows.

10 . The method as recited in claim 1 wherein the at least one energy storage cell includes a plurality of energy storage cells and the current measurement device is connected to each of the plurality of energy storage cells.

11 . The method as recited in claim 1 including an additional step of comparing the first impedance value with a predetermined impedance threshold value, the step of adjusting the rechargeable battery from the first state of charge to the second state of charge being blocked by the rechargeable battery controller if the first impedance value has reached the predetermined impedance threshold value.