Method and system for determining state of charge of an energy delivery device
원문보기
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
G01R-019/00
G01R-031/36
출원번호
US-0477382
(2009-06-03)
등록번호
US-8855956
(2014-10-07)
발명자
/ 주소
Thomas-Alyea, Karen E.
출원인 / 주소
A123 Systems LLC
대리인 / 주소
Alleman Hall McCoy Russell & Tuttle LLP
인용정보
피인용 횟수 :
1인용 특허 :
2
초록▼
A method of determining state of charge of an energy delivery device includes sampling voltage values of the energy delivery device during relaxation of the device. The method further includes regressing an open circuit voltage value and the total overpotential being relaxed. The regression includes
A method of determining state of charge of an energy delivery device includes sampling voltage values of the energy delivery device during relaxation of the device. The method further includes regressing an open circuit voltage value and the total overpotential being relaxed. The regression includes a predetermined time constant of relaxation associated with the energy delivery device. One embodiment uses the equation V(t)=OCV−α exp(−t/tau), where V(t) represents the sampled voltage values, t represents times at which each of the voltage values are sampled, OCV represents the open circuit voltage value of the energy delivery device, αrepresents the overpotential value, and tau represents the time constant of relaxation. The method uses a predetermined profile that relates open circuit voltage of the energy delivery device to state of charge of the device, to determine a particular state of charge corresponding to the regressed open circuit voltage value.
대표청구항▼
1. A method of determining state of charge of an energy delivery device using a battery management system, comprising: sampling, by the battery management system, voltage values presented by the energy delivery device during a relaxation period of the energy delivery device;regressing at the battery
1. A method of determining state of charge of an energy delivery device using a battery management system, comprising: sampling, by the battery management system, voltage values presented by the energy delivery device during a relaxation period of the energy delivery device;regressing at the battery management system, with respect to the sampled voltage values, (i) a first variable representing a real-time open circuit voltage value of the energy delivery device and (ii) a second variable representing a real-time overpotential value that describes a total overpotential being relaxed, wherein an equation used for regressing the open circuit voltage value and the overpotential value includes a time constant of relaxation, the time constant of relaxation being a fixed value that is (a) determined prior to the regressing and (b) determined as a function of the energy delivery device; andusing a predetermined profile that relates open circuit voltage of the energy delivery device to state of charge of the energy delivery device, to determine a particular state of charge corresponding to the regressed open circuit voltage value. 2. The method of claim 1, wherein the equation is V(t)=OCV−α exp(−t/tau), where V(t) represents the sampled voltage values, t represents times at which each of the voltage values are sampled, OCV is the first variable representing the open circuit voltage value of the energy delivery device, α is the second variable representing the overpotential value, and tau is the predetermined time constant of relaxation associated with the energy delivery device. 3. The method of claim 1, wherein the predetermined time constant of relaxation associated with the energy delivery device is generated by (i) applying a current to the energy delivery device,(ii) discontinuing the current after a period of time,(iii) recording voltages presented by the energy delivery device after the current is discontinued,(iv) plotting a logarithm of a plurality of differences Vt—last−Vt, wherein Vt—last is a final voltage recorded after the current is discontinued and Vt, is a voltage recorded at time t;(v) determining a slope of a linear fit to the plurality of differences Vt—last−Vt; wherein the predetermined time constant of relaxation is the inverse of the slope. 4. The method of claim 3, wherein the linear fit is determined using the differences Vt—last−Vt only for t greater than N seconds and less than M seconds after discontinuing the current, wherein M is a value selected according to a first time constant associated with a large diffusion component of the energy delivery device, and N is a value selected according to a second time constant associated with the energy delivery device that is substantially smaller than the first time constant. 5. The method of claim 3, wherein the predetermined time constant of relaxation is generated as a function of temperature of the energy delivery device. 6. The method of claim 3, wherein the predetermined time constant is determined as a function of state of health of the energy delivery device. 7. The method of claim 1, wherein the predetermined time constant of relaxation is chosen with respect to a measured temperature of the energy delivery device. 8. The method of claim 1, wherein a sampling interval associated with the sampling is chosen as a function of the predetermined time constant of relaxation of the energy delivery device. 9. The method of claim 1, wherein the regression uses only the sampled voltage values that were sampled more than N seconds after beginning the relaxation period. 10. The method of claim 1, further including combining the determined particular state of charge with one or more state of charge estimates determined by alternative estimating techniques. 11. The method of claim 10, wherein the alternative estimating techniques includes at least one of (i) coulomb counting, (ii) evaluation of an equivalent circuit model corresponding to the energy delivery device, (iii) evaluation of a physical cell model corresponding to the energy delivery device, (iv) measurements of one or more of voltage, temperature, a derivative of voltage and a derivative of temperature. 12. The method of claim 10, wherein the combining includes calculating a weighted sum of the determined particular state of charge and the one or more state of charge estimates determined by alternative techniques. 13. An apparatus for determining state of charge of an energy delivery device, comprising: a voltage measurement device for sampling voltage values presented by the energy delivery device during a relaxation period of the energy delivery device;a processor for regressing, with respect to the sampled voltage values, (i) a first variable representing a real-time open circuit voltage value of the energy delivery device and (ii) a second variable representing a real-time overpotential value that describes a total overpotential being relaxed, wherein equation used for regressing the open circuit voltage value and the overpotential value includes a time constant of relaxation, the time constant of relaxation being a fixed value that is (a) determined prior to the regressing and (b) determined as a function of the energy delivery device; andusing a predetermined profile that relates open circuit voltage of the energy delivery device to state of charge of the energy delivery device, to determine a particular state of charge corresponding to the regressed open circuit voltage value. 14. The apparatus of claim 13, wherein the equation is V(t)=OCV−α exp(−t/tau), where V(t) represents the sampled voltage values, t represents times at which each of the voltage values are sampled, OCV is the first variable representing the open circuit voltage value of the energy delivery device, α is the second variable representing the overpotential value, and tau is the predetermined time constant of relaxation associated with the energy delivery device. 15. The apparatus of claim 13, wherein the predetermined time constant of relaxation is chosen with respect to a measured temperature of the energy delivery device. 16. The apparatus of claim 13, wherein a sampling interval associated with the sampling is chosen as a function of the predetermined time constant of relaxation of the energy delivery device. 17. The apparatus of claim 13, wherein the regression uses only the sampled voltage values that were sampled more than N seconds after beginning the relaxation period. 18. The apparatus of claim 13, wherein the determined particular state of charge is combined with one or more state of charge estimates determined by alternative estimating techniques. 19. The apparatus of claim 18, wherein the alternative estimating techniques includes at least one of (i) coulomb counting, (ii) evaluation of an equivalent circuit model corresponding to the energy delivery device, (iii) evaluation of a physical cell model corresponding to the energy delivery device, (iv) measurements of one or more of voltage, temperature, a derivative of voltage and a derivative of temperature. 20. The apparatus of claim 18, wherein the combination of the determined particular state of charge and the one or more state of charge estimates determined by alternative estimating includes a weighted sum of the determined particular state of charge and the one or more state of charge estimates determined by alternative techniques. 21. A computer program product, including a non-transitory computer usable medium having a computer readable program code embodied therein, the computer readable program code adapted to be executed to implement a method of determining state of charge of an energy delivery device, the medium holding one or more instructions for: sampling voltage values presented by the energy delivery device during a relaxation period of the energy delivery device;regressing, with respect to the sampled voltage values, (i) a first variable representing a real-time open circuit voltage value of the energy delivery device and (ii) a second variable representing a real-time overpotential value that describes a total overpotential being relaxed, wherein an equation used for regressing the open circuit voltage value and the overpotential value includes a time constant of relaxation, the time constant of relaxation being a fixed value that is (a) determined prior to the regressing and (b) determined as a function of the energy delivery device; andusing a predetermined profile that relates open circuit voltage of the energy delivery device to state of charge of the energy delivery device, to determine a particular state of charge corresponding to the regressed open circuit voltage value. 22. The computer program product of claim 21, wherein the equation is V(t)=OCV−α exp(−t/tau), where V(t) represents the sampled voltage values, t represents times at which each of the voltage values are sampled, OCV is the first variable representing the open circuit voltage value of the energy delivery device α is the second variable representing the overpotential value, and tau is the predetermined time constant of relaxation associated with the energy delivery device.
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이 특허에 인용된 특허 (2)
Nguyen Trung V. (Lawrence KS), Method and apparatus for predicting the remaining capacity and reserve time of a battery on discharge.
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