Method for detecting state of secondary battery and device for detecting state of secondary battery

• US 7,688,033 B2
• Filed: 09/15/2005
• Issued: 03/30/2010
• Est. Priority Date: 09/29/2004
• Status: Active Grant

• Current Assignee: Panasonic EV Energy Company, Limited (Toyota Motor Corporation)
• Original Assignee: Panasonic EV Energy Company, Limited (Toyota Motor Corporation)
• Inventors: Minamiura, Keiichi
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): Boateng; Alexis
• Application Number:
  US11/227,535
• Publication Number:
  US 20060066285A1
• Time in Patent Office: 1,657 Days
• Field of Search: 320/134, 320/127, 320/132, 320/128, 320/138, 320/135, 320/116, 320/118, 320/148, 320/151, 320/152, 320/156, 320/157
• US Class Current: 320/134
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: H02J 7/0047 with monitoring or indicating devices or circuits

Abstract

Based on a plurality of valid data sets from a data set selection portion, an internal-resistance-during-charging calculation portion calculates the value Rc of internal resistance during charging from the slope of a voltage-current linear approximation during charging, and an internal-resistance-during-charging-and-discharging calculation portion calculates the value Rcd of internal resistance during charging and discharging from the slope of a voltage-current linear approximation during charging and discharging. A judgment portion compares the absolute value ΔR of the difference between Rcd and Rc that has been calculated by a difference computation portion with a first predetermined value ΔRT1, and when ΔR≦ΔRT1 is satisfied, the judgment portion outputs Rcd or Rc, whichever is smaller, as the value of internal resistance of a secondary battery.

Claims

1. A method for detecting the state of a secondary battery, comprising:

(a) a step of acquiring a plurality of data sets associating a current flowing through the secondary battery with a terminal voltage of the secondary battery corresponding to that current, wherein the plurality of data sets include (i) first data sets including first current data for the current in a charging direction and (ii) second data sets including second current data for the current in a discharging direction;

(b) a step of making the plurality of data sets valid when specific selection conditions are satisfied;

(c) a step of performing first statistical processing using the plurality of data sets including both the first data sets and the second data sets acquired during both charging and discharging, and calculating a first value of internal resistance in both the charging and discharging directions from the slope of a first linear approximation obtained by the first statistical processing;

(d) a step of performing second statistical processing using first data sets acquired during charging, and calculating a second value of internal resistance in the charging direction from the slope of a second linear approximation obtained by the second statistical processing; and

(e) a step of calculating a calculated value of internal resistance of the secondary battery based on the first value of internal resistance in both the charging and discharging directions and the second value of internal resistance in the charging direction.

2. The method for detecting the state of a secondary battery according to claim 1, further comprising:

a step of judging whether or not an absolute value of the difference between the first value of internal resistance in both the charging and discharging directions and the second value of internal resistance in the charging direction is equal to or less than a first predetermined value,

wherein, in step (e), when the absolute value of the difference between the first value of internal resistance in both the charging and discharging directions and the second value of internal resistance in the charging direction is equal to or less than the first predetermined value, then the calculated value of internal resistance of the secondary battery is calculated.

3. The method for detecting the state of a secondary battery according to claim 2, wherein, in step (e), when the absolute value of the difference between the first value of internal resistance in both the charging and discharging directions and the second value of internal resistance in the charging direction is equal to or less than the first predetermined value, then the first value of internal resistance in both the charging and discharging directions or the second value of internal resistance in the charging direction, whichever is smaller, is used as the calculated value of internal resistance of the secondary battery.

4. The method for detecting the state of a secondary battery according to claim 2, further comprising:

a step of judging whether or not the first value of internal resistance in both the charging and discharging directions is greater than the second value of internal resistance in the charging direction, and

a step of judging whether or not the difference between the first value of internal resistance in both the charging and discharging directions and the second value of internal resistance in the charging direction is greater than a second predetermined value that is greater than the first predetermined value,

wherein, in step (e), when the absolute value of the difference between the first value of internal resistance in both the charging and discharging directions and the second value of internal resistance in the charging direction is greater than the first predetermined value, and further the first value of internal resistance in both the charging and discharging directions is greater than the second value of internal resistance in the charging direction and the difference between the first value of internal resistance in the charging and discharging directions and the second value of internal resistance in both the charging direction is greater than the second predetermined value, then a judgment that the secondary battery has deteriorated is made instead of calculating the calculated value of internal resistance of the secondary battery.

5. The method for detecting the state of a secondary battery according to claim 4, further comprising a step of setting the first predetermined value and a second predetermined value according to the temperature of the secondary battery.

6. The method for detecting the state of a secondary battery according to claim 1, wherein the specific selection conditions are conditions that are dependent on at least a change in the amount of stored charge of the secondary battery in a predetermined period of time, ranges of current values of the secondary battery in a charging direction and a discharging direction, numbers of the data sets in the charging direction and the discharging direction, and the temperature of the secondary battery.

7. A device for detecting the state of a secondary battery, comprising:

a current measurement portion that measures the current flowing through the secondary battery as current data;

a voltage measurement portion that measures the terminal voltage of the secondary battery as voltage data;

a data set selection portion that acquires a plurality of data sets comprising the current data from the current measurement portion and the voltage data from the voltage measurement portion that corresponds to the current data, and that outputs the plurality of data sets as valid data sets when specific selection conditions are satisfied, wherein the plurality of data sets include (i) first data sets that include first current data for the current in a charging direction and (ii) second data sets including second current data for the current in the discharging direction;

an internal-resistance-during-charging-and-discharging calculation portion that performs statistical processing on the plurality of data sets including the valid first data sets and the valid second data sets acquired during both charging and discharging, and calculating a first value of internal resistance in both the charging and discharging directions from the slope of a linear approximation obtained by the statistical processing;

an internal-resistance-during-charging calculation portion that performs statistical processing using the valid first data sets acquired during charging, and calculating a second value of internal resistance in the charging direction from the slope of a linear approximation obtained by the statistical processing;

a difference computation portion that calculates an absolute value of the difference between the first value of internal resistance in both the charging and discharging directions and the second value of internal resistance in the charging direction, and that also outputs a signal indicating the magnitude correlation between the first value of internal resistance in both the charging and discharging directions and the second value of internal resistance in the charging direction; and

a judgment portion that judges whether or not the absolute value of the difference from the difference computation portion is equal to or less than a first predetermined value, and that outputs the first value of internal resistance in both the charging and discharging directions or the second value of internal resistance in the charging direction, whichever is smaller, as a calculated value of internal resistance of the secondary battery when the absolute value of the difference is equal to or less than the first predetermined value.

8. The device for detecting the state of a secondary battery according to claim 7, wherein when the absolute value of the difference between the first value of internal resistance in both the charging and discharging directions and the second value of internal resistance in the charging direction is greater than the first predetermined value, and further the first value of internal resistance in both the charging and discharging directions and discharging is greater than the second value of internal resistance in the charging direction and the difference between the first value of internal resistance in both the charging and discharging directions and the second value of internal resistance in the charging direction is greater than a second predetermined value that is greater than the first predetermined value, then the judgment portion judges that the secondary battery has deteriorated.

9. The device for detecting the state of a secondary battery according to claim 8, further comprising:

a temperature measurement portion that measures the temperature of the secondary battery; and

a predetermined value setting portion that sets the first predetermined value and a second predetermined value according to the temperature of the secondary battery.

10. The device for detecting the state of a secondary battery according to claim 7, further comprising:

a stored charge amount change calculation portion that obtains a change in the amount of stored charge of the secondary battery in a predetermined period of time; and

a temperature measurement portion that measures the temperature of the secondary battery,

wherein when the specific selection conditions comprising at least the change in the amount of stored charge in the predetermined period of time, ranges of current values of the secondary battery in a charging direction and a discharging direction, numbers of the data sets in the charging direction and the discharging direction, the temperature of the secondary battery, and a deviation in the temperature of the secondary battery are satisfied, then the data set selection portion makes the plurality of data sets valid.