Apparatus for estimating depth of discharge (DOD) of secondary battery
View Patent ↗Disclosed is an apparatus and method for estimating a parameter of a secondary battery. The apparatus includes a sensor unit configured to repeatedly measure a voltage of a secondary battery including a blended cathode material containing at least first and second cathode materials at time intervals when the secondary battery is in an operation state or in an idle state, and a control unit configured to receive the repeatedly measured plurality of voltages from the sensor unit, identify an inflection point in a voltage change profile corresponding to the plurality of voltages, and estimate a depth of discharge (DOD) of the secondary battery by using a voltage measured after the inflection point is identified as a reference voltage.
1. An apparatus for estimating a depth of discharging (DOD) of a secondary battery, comprising:
a sensor unit configured to repeatedly measure a voltage of a secondary battery including a blended cathode material containing at least first and second cathode materials at time intervals when the secondary battery is in an operation state or in an idle state; and
a control unit configured to:
receive the repeatedly measured plurality of voltages from the sensor unit,
identify an inflection point indicative of changing of a cathode material reacting with working ions in a voltage change over time profile corresponding to the plurality of voltages,
measure a voltage a predetermined time after the inflection point, and
estimate a DOD of the secondary battery by using the voltage measured after the inflection point is identified as a reference voltage.
2. The apparatus for estimating a DOD of a secondary battery according to claim 1 , wherein the control unit is configured to estimate the DOD by using a voltage measured after a predetermined time since the inflection point is identified as a reference voltage.
3. The apparatus for estimating a DOD of a secondary battery according to claim 1 , wherein the control unit is configured to estimate the DOD by using a lookup table or a lookup function which defines a correlation between the reference voltage and the DOD in advance.
4. The apparatus for estimating a DOD of a secondary battery according to claim 1 , wherein the control unit is configured to identify the inflection point when a voltage change rate (dV/dt) with respect to time is at the maximum in the voltage change profile.
5. The apparatus for estimating a DOD of a secondary battery according to claim 1 , wherein the secondary battery has an open-circuit voltage profile including at least one inflection point or a discharge resistance profile including a convex pattern.
6. The apparatus for estimating a DOD of a secondary battery according to claim 1 , further comprising:
a storage unit configured to store the estimated DOD;
a display unit configured to display the estimated DOD; or
a communication interface configured to transmit the estimated DOD to the outside.
7. An electric-powered device, which comprises the apparatus for estimating a DOD of a secondary battery as defined in the claim 1 .
8. An apparatus for estimating a DOD of a secondary battery, comprising:
a sensor unit configured to repeatedly measure a voltage of a secondary battery including a blended cathode material containing at least first and second cathode materials at time intervals when the secondary battery is in an operation state or in an idle state; and
a control unit configured to
receive the repeatedly measured plurality of voltages from the sensor unit, identify an inflection point indicative of changing of a cathode material reacting with working ions in a voltage change over time profile corresponding to the plurality of voltages,
estimate a reference voltage, which is to be used for estimating a DOD of the secondary battery, by means of extrapolation from a plurality of voltages measured at predetermined times after the inflection point is identified, and
estimate the DOD by using the reference voltage.
9. The apparatus for estimating a DOD of a secondary battery according to claim 8 , wherein the control unit is configured to determine an approximation function for approximating a voltage change profile corresponding to the plurality of voltages measured after the inflection point is identified, and estimate a voltage corresponding to a predetermined time as the reference voltage by using the approximation function.
10. The apparatus for estimating a DOD of a secondary battery according to claim 8 , wherein the control unit is configured to estimate the DOD by using a lookup table or a lookup function which defines a correlation between the reference voltage and the DOD in advance.
11. The apparatus for estimating a DOD of a secondary battery according to claim 8 , wherein the control unit is configured to identify the inflection point when a voltage change rate (dV/dt) with respect to time is at the maximum in the voltage change profile.
12. The apparatus for estimating a DOD of a secondary battery according to claim 8 , wherein the secondary battery has an open-circuit voltage profile including at least one inflection point or a discharge resistance profile including a convex pattern.
13. The apparatus for estimating a DOD of a secondary battery according to claim 8 , further comprising:
a storage unit configured to store the estimated DOD;
a display unit configured to display the estimated DOD; or
a communication interface configured to transmit the estimated DOD to the outside.
14. An electric-powered device, which comprises the apparatus for estimating a DOD of a secondary battery as defined in the claim 8 .
15. A method for estimating a DOD of a secondary battery, comprising:
(a) receiving a plurality of voltages of a secondary battery, which have been repeatedly measured at time intervals when the secondary battery including a blended cathode material containing at least first and second cathode materials is in an operation state or in an idle state;
(b) identifying an inflection point indicative of changing of a cathode material reacting with working ions in a voltage change over time profile corresponding to the plurality of voltages;
(c) selecting a voltage, measured a predetermined time after the inflection point is identified, as a reference voltage; and
(d) estimating a DOD of the secondary battery by using the reference voltage.
16. The method for estimating a DOD of a secondary battery according to claim 15 , wherein in the step (b), the inflection point is identified when a voltage change rate (dV/dt) with respect to time is at the maximum in the voltage change profile.
17. The method for estimating a DOD of a secondary battery according to claim 15 , wherein in the step (c), a voltage measured after a predetermined time since the inflection point is identified is selected as a reference voltage.
18. The method for estimating a DOD of a secondary battery according to claim 15 , wherein in the step (d), the DOD is estimated by using a lookup table or a lookup function which defines a correlation between the reference voltage and the DOD in advance.
19. The method for estimating a DOD of a secondary battery according to claim 15 , further comprising:
storing, displaying or transmitting the estimated DOD.
20. A method for estimating a DOD of a secondary battery, comprising:
(a) receiving a plurality of voltages of a secondary battery, which have been repeatedly measured at time intervals when the secondary battery including a blended cathode material containing at least first and second cathode materials is in an operation state or in an idle state;
(b) identifying an inflection point indicative of changing of a cathode material reacting with working ions in a voltage change over time profile corresponding to the plurality of voltages;
(c) estimating a reference voltage, which is to be used for estimating a DOD of the secondary battery, by means of extrapolation from a plurality of voltages measured at predetermined times after the inflection point is identified; and
(d) estimating the DOD by using the estimated reference voltage.
21. The method for estimating a DOD of a secondary battery according to claim 20 , wherein in the step (b), the inflection point is identified when a voltage change rate (dV/dt) with respect to time is at the maximum in the voltage change profile.
22. The method for estimating a DOD of a secondary battery according to claim 20 , wherein in the step (c), an approximation function for approximating a voltage change profile corresponding to the plurality of voltages measured after the inflection point is identified is determined, and a voltage corresponding to a predetermined time is estimated as the reference voltage by using the approximation function.
23. The method for estimating a DOD of a secondary battery according to claim 20 , wherein in the step (d), the DOD is estimated by using a lookup table or a lookup function which defines a correlation between the reference voltage and the DOD in advance.
24. The method for estimating a DOD of a secondary battery according to claim 20 , further comprising:
storing, displaying or transmitting the estimated DOD.