State of charge determination for an electrical accumulator

• US 9,450,427 B2
• Filed: 07/30/2009
• Issued: 09/20/2016
• 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
• Primary Examiner(s): Rodas, Richard Isla
• Assistant Examiner(s): TORRES RUIZ, JOHALI ALEJANDRA
• Application Number:
  US12/737,667
• Publication Number:
  US 20110187378A1
• Time in Patent Office: 2,609 Days
• Field of Search: 324/427
• US Class Current: 1/1
• 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 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/0049 Detection of fully charged condition
• 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. A method for operating an electrical accumulator based on a state of charge of the electrical accumulator, the electrical accumulator including a plurality of accumulator cells, the plurality of cells including at least three cells, for which a characteristics curve describes an electrical charge as a function of cell voltage in a load free state, the method comprising:

in a first recording period, recording individual cell voltages of respective ones of the plurality of accumulator cells in the load free state;

in a first charge determining process, at least one of;

(A);

(i) ascertaining which of the recorded individual cell voltages is the highest of the recorded individual cell voltages; and

(ii) ascertaining, as a present maximum charge, a charge value identified by the characteristics curve as corresponding to a value of the ascertained highest of the recorded individual cell voltages; and

(B);

(i) ascertaining which of the recorded individual cell voltages is the lowest of the recorded individual cell voltages; and

(ii) ascertaining, as a present minimum charge, a charge value identified by the characteristics curve as corresponding to a value of the ascertained lowest of the recorded individual cell voltages;

in a second recording period, recording a respective individual cell voltage of each of only the at least one cell for which the at least one of the highest and lowest of the recorded individual cell voltages was ascertained in the first charge determining process; and

in a second charge determining process, re-ascertaining the at least one of the present minimum charge and the present maximum charge based on the at least one respective individual cell voltage recorded in the second recording period; and

controlling at least one of a charging of the accumulator and a discharging of the accumulator based on the at least one of the present minimum charge and the present maximum charge ascertained in the second charge determining process.

2. The method as recited in claim 1, wherein electrical load current of the accumulator is recorded in a load state of the accumulator.

3. The method as recited in claim 1, wherein each accumulator cell has at least one of an upper charge limit and a lower charge limit according to which the controlling is performed.

4. The method as recited in claim 3, wherein, in the controlling, 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.

5. The method as recited in claim 3, wherein, in the controlling, 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.

6. The method as recited in claim 1, wherein the method includes the ascertaining of which of the recorded individual cell voltages is the highest of the recorded individual cell voltages, and the ascertaining, as the present maximum charge, of the charge value identified by the characteristics curve as corresponding to the value of the ascertained highest of the recorded individual cell voltages.

7. The method as recited in claim 1, wherein the method includes the ascertaining of which of the recorded individual cell voltages is the lowest of the recorded individual cell voltages, and the ascertaining, as the present minimum charge, of the charge value identified by the characteristics curve as corresponding to the value of the ascertained lowest of the recorded individual cell voltages.

8. A method for operating an electrical accumulator based on a state of charge of the electrical accumulator, the electrical accumulator including a plurality of accumulator cells for which a characteristics curve describes an electrical charge as a function of cell voltage in a load free state, the method comprising:

recording individual cell voltages of respective ones of the plurality of accumulator cells in the load free state;

at least one of;

(A);

(i) ascertaining which of the recorded individual cell voltages is the highest of the recorded individual cell voltages; and

(ii) ascertaining, as a present maximum charge in the load free state, a charge value identified by the characteristics curve as corresponding to a value of the ascertained highest of the recorded individual cell voltages; and

(B);

(i) ascertaining which of the recorded individual cell voltages is the lowest of the recorded individual cell voltages; and

(ii) ascertaining, as a present minimum charge in the load free state, a charge value identified by the characteristics curve as corresponding to a value of the ascertained lowest of the recorded individual cell voltages;

recording electrical load current of the accumulator in a load state of the accumulator;

at least one of;

calculating for the load state the present maximum charge of the accumulator cell for which the highest of the recorded individual cell voltages was previously ascertained in (A)(i) for the load free state, using the recorded electrical load current and the duration of the electrical load current to modify the maximum charge ascertained in (A)(ii) for the load-free state; and

calculating for the load state the present minimum charge of the accumulator cell for which the lowest of the recorded individual cell voltages was previously ascertained in (B)(i) for the load free state, using the recorded electrical load current and the duration of the electrical load current to modify the minimum charge ascertained in (B)(ii) for the load-free state; and

controlling at least one of a charging of the accumulator and a discharging of the accumulator based on the at least one of the present minimum charge and the present maximum charge calculated for the load state.

9. The method as recited in claim 8, wherein the calculating of the present maximum charge is performed.

10. The method as recited in claim 8, wherein the calculating of the present minimum charge is performed.

11. A method for operating an electrical accumulator based on a state of charge of the electrical accumulator, the electrical accumulator including a plurality of accumulator cells for which a characteristics curve describes an electrical charge as a function of cell voltage in a load free state, the method comprising:

recording individual cell voltages of respective ones of the plurality of accumulator cells in the load free state;

at least one of;

(A);

(i) ascertaining which of the recorded individual cell voltages is the highest of the recorded individual cell voltages; and

(ii) ascertaining, as a present maximum charge, a charge value identified by the characteristics curve as corresponding to a value of the ascertained highest of the recorded individual cell voltages; and

(B);

(i) ascertaining which of the recorded individual cell voltages is the lowest of the recorded individual cell voltages; and

(ii) ascertaining, as a present minimum charge, a charge value identified by the characteristics curve as corresponding to a value of the ascertained lowest of the recorded individual cell voltages; and

controlling at least one of a charging of the accumulator and a discharging of the accumulator based on the at least one ascertained charge;

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 value specified as being a maximum current that can be provided with the accumulator.

12. The method as recited in claim 11, wherein, for the selected state of charge of the accumulator, the maximum power output of the accumulator is calculated additionally using the number of accumulator cells.

13. A device for operating an electrical accumulator based on a state of charge of the electrical accumulator, the electrical accumulator including a plurality of accumulator cells for which a characteristics curve describes an electrical charge as a function of cell voltage in a load free state, the device comprising:

an individual cell voltage recording device configured to record individual cell voltages of the plurality of accumulator cells in the load free state;

a data memory storing the characteristics curve;

a current-recording device for recording electrical load current of the accumulator in a load state of the accumulator; and

circuitry configured to;

(1) at least one of;

(A);

(i) ascertain which of the recorded individual cell voltages is the highest of the recorded individual cell voltages; and

(ii) ascertain, as a present maximum charge in the load free state, a charge value identified by the characteristics curve as corresponding to a value of the ascertained highest of the recorded individual cell voltages; and

(B);

(i) ascertain which of the recorded individual cell voltages is the lowest of the recorded individual cell voltages; and

(ii) ascertain, as a present minimum charge in the load free state, a charge value identified by the characteristics curve as corresponding to a value of the ascertained lowest of the recorded individual cell voltages;

(2) at least one of;

calculate for the load state the present maximum charge of the accumulator cell, for which the highest of the recorded individual cell voltages was previously ascertained in (A)(i) for the load free state, using the recorded electrical load current and the duration of the electrical load current to modify the maximum charge ascertained in (A)(ii) for the load-free state; and

calculate for the load state the present minimum charge of the accumulator cell, for which the lowest of the recorded individual cell voltages was previously ascertained in (B)(i) for the load free state, using the recorded electrical load current and the duration of the electrical load current to modify the minimum charge ascertained in (B)(ii) for the load-free state; and

(3) control at least one of a charging of the accumulator and a discharging of the accumulator based on the at least one of the present minimum charge and the present maximum charge calculated for the load state.

14. The device as recited in claim 13, further comprising:

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

15. The device as recited in claim 13, wherein the device is configured as a control unit for a motor vehicle.

16. The device as recited in claim 13, wherein the circuitry is configured to perform the ascertainment of which of the recorded individual cell voltages is the highest of the recorded individual cell voltages, and the ascertainment, as the present maximum charge, of the charge value identified by the characteristics curve as corresponding to the value of the ascertained highest of the recorded individual cell voltages.

17. The device as recited in claim 13, wherein the circuitry is configured to perform the ascertainment of which of the recorded individual cell voltages is the lowest of the recorded individual cell voltages, and the ascertainment, as the present minimum charge, of the charge value identified by the characteristics curve as corresponding to the value of the ascertained lowest of the recorded individual cell voltages.

18. A method for operating an electrical accumulator based on a state of charge of the electrical accumulator, the electrical accumulator including a plurality of accumulator cells for which a characteristics curve describes an electrical charge as a function of cell voltage, the method comprising:

recording individual cell voltages of respective ones of the plurality of accumulator cells in a load free state;

ascertaining which of the recorded individual cell voltages is the highest of the recorded individual cell voltages;

ascertaining, as a present maximum charge in the load free state, a charge value identified by the characteristics curve as corresponding to a value of the ascertained highest of the recorded individual cell voltages;

ascertaining which of the recorded individual cell voltages is the lowest of the recorded individual cell voltages;

ascertaining, as a present minimum charge in the load free state, a charge value identified by the characteristics curve as corresponding to a value of the ascertained lowest of the recorded individual cell voltages;

recording electrical load current of the accumulator in a load state of the accumulator that follows the load free state in which the individual cell voltages were recorded;

calculating for the load state the present maximum charge of the accumulator cell, for which the highest of the recorded individual cell voltages was previously ascertained for the load free state, using the recorded electrical load current and the duration of the electrical load current to modify the maximum charge ascertained for the load-free state;

calculating for the load state the present minimum charge of the accumulator cell, for which the lowest of the recorded individual cell voltages was previously ascertained for the load free state, using the recorded electrical load current and the duration of the electrical load current to modify the minimum charge ascertained in for the load-free state; and

controlling at least one of a charging of the accumulator and a discharging of the accumulator based on at least one of the present minimum charge and the present maximum charge calculated for the load state.