STATE OF CHARGE DETERMINATION FOR AN ELECTRICAL ACCUMULATOR

• US 20110187378A1
• Filed: 07/30/2009
• Published: 08/04/2011
• Est. Priority Date: 08/07/2008
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Boehm, Andre, Liedtke, Ralf, Kern, Rainer
• Granted Patent: US 9,450,427 B2
• Time in Patent Office: Days
• US Class Current: 324/427
• CPC Class Codes: B60L 58/15 Preventing overcharging
• CPC Class Codes: G01R 31/388 involving voltage measurements
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H02J 7/0047 with monitoring or indicating devices or circuits
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

In a method for determining the state of charge of an electrical accumulator, individual cell voltages are recorded, and the highest and/or the lowest individual cell voltage is ascertained. A present maximum charge and/or a present minimum charge of the appertaining accumulator cell is determined using a characteristic curve and the highest and/or the lowest individual cell voltage.

Claims

1-16. -16. (canceled)

17. A method for determining the state of charge of an electrical accumulator including at least three accumulator cells each having the same characteristics curve in the load-free state, wherein the characteristics curve describes an electrical charge of the respective accumulator cell as a function of the individual cell voltage, the method comprising:

recording individual cell voltages of the at least three accumulator cells;

ascertaining at least one of the highest recorded individual cell voltage and the lowest recorded individual cell voltage; and

ascertaining at least one of;

(i) a present maximum charge of a selected one of the at least three accumulator cells using the characteristics curve and the highest recorded individual cell voltage; and

(ii) a present minimum charge of a selected one of the at least three accumulator cells using the characteristics curve and the lowest recorded individual cell voltage.

18. The method as recited in claim 17, wherein the individual cell voltages are recorded in the load-free state.

19. The method as recited in claim 18, wherein, in at least one of a predetermined time interval and a predetermined operating interval of the accumulator associated with each new load-free state, the individual cell voltages are recorded again and the at least one of the maximum charge and the minimum charge is ascertained again.

20. The method as recited in claim 19, wherein, subsequent to the first load-free state, only the individual cell voltages of the accumulator cells which in the first load-free state exhibited the at least one of the highest recorded individual cell voltage and the lowest recorded individual cell voltage are recorded.

21. The method as recited in claim 17, wherein electrical load current of the accumulator is recorded in a load state of the accumulator.

22. The method as recited in claim 21, wherein the present maximum charge of the selected one of the accumulator cells is calculated in the load state using the recorded electrical load current, the duration of the electrical load current, and the maximum charge of the selected one of the accumulator cells recorded in the preceding load-free state.

23. The method as recited in claim 21, wherein the present minimum charge of the selected one of the accumulator cells is calculated in the load state using the recorded electrical load current, the duration of the electrical load current, and the minimum charge of the selected one of the accumulator cells recorded in the preceding load-free state.

24. The method as recited in claim 18, wherein each accumulator cell has at least one of an upper charge limit and a lower charge limit.

25. The method as recited in claim 24, wherein the accumulator is charged until the charge state of at least one accumulator cell is equal to the upper charge limit of the at least one accumulator cell.

26. The method as recited in claim 24, wherein the accumulator is discharged until the charge state of at least one accumulator cell is equal to the lower charge limit of the at least one accumulator cell.

27. The method as recited in claim 18, wherein, for a selected state of charge of the accumulator, maximum power output of the accumulator is calculated using the number of accumulator cells, the lowest recorded individual cell voltage and a specified maximum current of the accumulator.

28. The method as recited in claim 18, wherein, for a selected state of charge of the accumulator, maximum power output of the accumulator is calculated using the lowest recorded individual cell voltage and a specified maximum current of the accumulator.

29. A device for determining the state of charge of an electrical accumulator including at least three accumulator cells each having the same characteristics curve in the load-free state, wherein the characteristics curve describes an electrical charge of the respective accumulator cell as a function of the individual cell voltage, the device comprising:

an individual cell voltage recording device configured to record individual cell voltages of the at least three accumulator cells;

a comparator device configured to ascertain at least one of the highest recorded individual cell voltage and the lowest recorded individual cell voltage;

a data memory storing the characteristics curve; and

a comparator device configured to ascertain at least one of;

(i) a present maximum charge of a selected one of the at least three accumulator cells using the characteristics curve and the highest recorded individual cell voltage; and

(ii) a present minimum charge of a selected one of the at least three accumulator cells using the characteristics curve and the lowest recorded individual cell voltage.

30. The device as recited in claim 29, further comprising:

a current-recording device for determining a load state of the accumulator.

31. The device as recited in claim 29, further comprising:

a charge calculation unit for determining a load state of the accumulator.

32. The device as recited in claim 30, wherein the device is configured as a control unit for a motor vehicle.