METHOD AND DEVICE FOR DETERMINING A CHARGE STATE OF AN ELECTRIC ENERGY STORE

• US 20140365150A1
• Filed: 12/21/2012
• Published: 12/11/2014
• Est. Priority Date: 01/12/2012
• Status: Abandoned Application

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Hahn, Alexander, Rabbers, Jacob Johan, Weydanz, Wolfgang, Wolfschmidt, Holger
• Application Number:
  US14/370,816
• Publication Number:
  US 20140365150A1
• Time in Patent Office: Days
• US Class Current: 702/63
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/378 specially adapted for the type of battery or accumulator
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements

Abstract

A method for determining a charge state of an electric energy store, having the following steps: measuring a voltage of the electric energy store on the basis of a charge quantity which is removed from or supplied to the electric energy store as a voltage characteristic curve and ascertaining a virtual open-circuit voltage characteristic curve from the measured voltage using at least one operating parameter of the electric energy store, ascertaining a first derivative and/or a second derivative of the virtual open-circuit voltage characteristic curve according to the charge quantity removed from or supplied to the electric energy store, detecting at least one characteristic of the first derivative and/or the second derivative of the virtual open-circuit voltage characteristic curve, and determining the charge state of the electric energy store using the detected at least one characteristic, is provided.

Claims

1. A method for determining a state of charge of an electrical energy store, comprising:

measuring, as a voltage characteristic curve, a voltage of the electrical energy store as a function of an amount of charge drawn from or supplied to the electrical energy store and calculating a virtual no-load voltage characteristic curve from the measured voltage, taking into account at least one operating parameter of the electrical energy store;

calculating a first derivative and/or a second derivative of the virtual no-load voltage characteristic curve according to the amount of charge drawn from or supplied to the electrical energy store;

capturing at least one characteristic of the first derivative and/or of the second derivative of the virtual no-load voltage characteristic curve; and

determining the state of charge of the electrical energy store on a basis of the captured at least one characteristic.

2. The method as claimed in claim 1, wherein a temperature of the electrical energy store and/or a current loading of the electrical energy store and/or an internal resistance of the electrical energy store and/or a hysteresis of the voltage of the electrical energy store is calculated as the at least one operating parameter of the electrical energy store.

3. The method as claimed in claim 1, wherein the voltage is measured by a sensor device and the amount of charge drawn from or supplied to the electrical energy store is captured by the sensor device during the measurement.

4. The method as claimed in claim 1, wherein a profile of the virtual no-load voltage of the electrical energy store against the amount of charge drawn from or supplied to the electrical energy store is captured with the virtual no-load voltage characteristic curve.

5. The method as claimed in claim 1, wherein the state of charge of the electrical energy store is determined on a basis of a comparison of the captured at least one characteristic of the virtual no-load voltage characteristic curve with voltage characteristic curves stored in a storage unit.

6. The method as claimed in claim 1, wherein a zero-point region of the first derivative is used as the at least one characteristic of the first derivative.

7. The method as claimed in claim 1, wherein a zero-point region and/or a region of the second derivative having a change of mathematical sign is used as the at least one characteristic of the second derivative.

8. The method as claimed in claim 1, wherein a peak value or a predetermined limit value of the first derivative and/or of the second derivative of the virtual no-load voltage characteristic curve is used as the at least one characteristic of the first derivative and/or of the second derivative of the virtual no-load voltage characteristic curve.

9. The method as claimed in claim 1, wherein the state of charge of the electrical energy store is determined on the basis of a curvature and/or on a basis of a gradient of the virtual no-load voltage characteristic curve.

10. The method as claimed in claim 9, wherein the curvature and/or the gradient of the virtual no-load voltage characteristic curve is determined in a predefinable edge region of the virtual no-load voltage characteristic curve.

11. The method as claimed in claim 1, wherein a disconnection limit of a minimum or maximum voltage of the electrical energy store is prevented from being reached by determining the state of charge of the electrical energy store.

12. The method as claimed in claim 1, wherein a lithium-ion battery with a two-phase material or with another material which has a flat discharge characteristic curve as active material is used as the electrical energy store.

13. The method as claimed in claim 1, wherein a lithium-ion battery with lithium-iron-phosphate or with lithium-manganese-phosphate or with lithium-cobalt-phosphate or with another lithium-metal-phosphate as cathode material is used as the electrical energy store.

14. The method as claimed in claim 1, wherein a lithium-ion battery with lithium titanate as active material is used as the electrical energy store.

15. The method as claimed in claim 1, wherein the amount of charge drawn from or supplied to the electrical energy store is calculated in steps of 0.1%-1% of a maximum state of charge of the electrical energy store.

16. A computer program for performing the method for determining a state of charge of an electrical energy store as claimed in claim 1.

17. A device for determining a state of charge of an electrical energy store, comprising:

a sensor device for measuring an amount of charge drawn from or supplied to the electrical energy store and for measuring, as a voltage characteristic curve, a voltage of the electrical energy store as a function of the amount of charge drawn from or supplied to the electrical energy store;

a storage unit with stored voltage characteristic curve data; and

a control device for calculating a virtual no-load voltage characteristic curve from the measured voltage, taking into account at least one operating parameter of the electrical energy store, for calculating a first derivative and/or a second derivative of the virtual no-load voltage characteristic curve according to the amount of charge drawn from or supplied to the electrical energy store, for capturing at least one characteristic of the first derivative and/or of the second derivative of the virtual no-load voltage characteristic curve and for determining the state of charge of the electrical energy store on the basis of the captured at least one characteristic.

18. The device as claimed in claim 17, wherein the sensor device is configured to capture, with the voltage characteristic curve, a profile of the voltage of the electrical energy store against the amount of charge drawn from or supplied to the electrical energy store.

19. The device as claimed in claim 17, wherein the control device is configured to determine the state of charge of the electrical energy store on a basis of a comparison of the captured at least one characteristic with voltage characteristic curve data stored in a storage unit.

20. The device as claimed in claim 17, wherein a temperature of the electrical energy store and/or a current loading of the electrical energy store and/or an internal resistance of the electrical energy store and/or a hysteresis of the voltage of the electrical energy store is provided as the at least one operating parameter of the electrical energy store.