Methods and apparatus for sensing the internal temperature of an electrochemical device
The internal temperature of an electrochemical device may be probed without a thermocouple, infrared detector, or other auxiliary device to measure temperature. Some methods include exciting an electrochemical device with a driving profile; acquiring voltage and current data from the electrochemical device, in response to the driving profile; calculating an impulse response from the current and voltage data; calculating an impedance spectrum of the electrochemical device from the impulse response; calculating a state-of-charge of the electrochemical device; and then estimating internal temperature of the electrochemical device based on a temperature-impedance-state-of-charge relationship. The electrochemical device may be a battery, fuel cell, electrolytic cell, or capacitor, for example. The procedure is useful for on-line applications which benefit from real-time temperature sensing capabilities during operations. These methods may be readily implemented as part of a device management and safety system.
1. A method of estimating the internal temperature of an electrochemical device, said method comprising:
(a) exciting said electrochemical device with a driving profile;
(b) acquiring voltage and current data from said electrochemical device, in response to said driving profile;
(c) calculating an impulse response from said current and voltage data and time derivatives thereof, using a recursive or matrix-based technique;
(d) calculating an impedance spectrum of said electrochemical device from said impulse response using an impulse response model;
(e) calculating a state-of-charge of said electrochemical device;
(f) estimating an internal temperature of said electrochemical device based on a temperature-impedance-state-of-charge relationship characterizing said electrochemical device; and
(g) managing said electrochemical device by adjusting electrical current and/or voltage to or from said electrochemical device in response to said internal temperature.
2. The method of claim 1 , wherein said driving profile includes a plurality of double-pulse sequences, wherein each of said double-pulse sequences comprises a constant-current discharge pulse having a pulse width and a pulse amplitude, a constant-current charge pulse having said pulse width and said pulse amplitude, and a zero-current period.
3. The method of claim 1 , wherein step (c) utilizes a Kalman filtering technique.
4. The method of claim 1 , wherein said recursive or matrix-based method utilizes a moving window to update time-varying electrical responses.
5. The method of claim 1 , wherein said impulse response model is a finite impulse response digital filter or an infinite impulse response digital filter.
6. The method of claim 1 , wherein said impedance spectrum in step (d) is calculated in a frequency range of 0.01 Hz to 1000 Hz.
7. The method of claim 6 , wherein said frequency range is 0.1 Hz to 1 Hz.
8. The method of claim 1 , wherein step (e) comprises calculating the Fourier transform of said impulse response to obtain said state-of-charge.
9. The method of claim 1 , wherein step (e) comprises calculating said state-of-charge based on an initial open-circuit voltage and Coulomb counting.
10. The method of claim 1 , wherein said temperature-impedance-state-of-charge relationship is in the form of an empirical look-up table or graph that is applicable to said electrochemical device or a theoretical equation correlating impedance with temperature and state-of-charge.
11. The method of claim 1 , wherein said method is implemented in a temperature safety device within a temperature range selected from −30° C. to 120° C.
12. The method of claim 1 , said method further comprising repeating steps (a)-(g) continually or periodically during operation of said electrochemical device.
13. A temperature-sensing apparatus for estimating the internal temperature of an electrochemical device, wherein said temperature-sensing apparatus is a temperature safety device within a temperature range selected from −30° C. to 120° C., and wherein said apparatus comprises a computer that is electrically linkable to said electrochemical device; said computer programmed using non-transitory memory with executable code for executing the steps of:
(a) exciting said electrochemical device with a driving profile;
(b) acquiring voltage and current data from said electrochemical device, in response to said driving profile;
(c) calculating an impulse response from said current and voltage data and time derivatives thereof, using a recursive or matrix-based technique;
(d) calculating an impedance spectrum of said electrochemical device from said impulse response using an impulse response model;
(e) calculating a state-of-charge of said electrochemical device;
(f) estimating an internal temperature of said electrochemical device based on a temperature-impedance-state-of-charge relationship characterizing said electrochemical device; and
(g) managing said electrochemical device by adjusting electrical current and/or voltage to or from said electrochemical device in response to said internal temperature.
14. A temperature-monitored electrochemical system comprising said temperature-sensing apparatus of claim 13 , wherein said temperature-sensing apparatus is electrically linked to said electrochemical device.
15. The temperature-monitored electrochemical system of claim 14 , wherein said electrochemical device is selected from the group consisting of a battery, a fuel cell, an electrolytic cell, a capacitor, a supercapacitor, a pseudocapacitor, an electroplating system, and a galvanic corrosion system.
16. The temperature-monitored electrochemical system of claim 14 , wherein said driving profile includes a plurality of double-pulse sequences, wherein each of said double-pulse sequences comprises a constant-current discharge pulse having a pulse width and a pulse amplitude, a constant-current charge pulse having said pulse width and said pulse amplitude, and a zero-current period.
17. The temperature-monitored electrochemical system of claim 14 , wherein step (c) utilizes a Kalman filtering technique.
18. The temperature-monitored electrochemical system of claim 14 , wherein said recursive or matrix-based technique utilizes a moving window to update time-varying electrical responses.
19. The temperature-monitored electrochemical system of claim 14 , wherein said impulse response model is a finite impulse response digital filter or an infinite impulse response digital filter.
20. The temperature-monitored electrochemical system of claim 14 , wherein said impedance spectrum in step (d) is estimated in a frequency range of 0.01 Hz to 1000 Hz.
21. The temperature-monitored electrochemical system of claim 20 , wherein said frequency range is 0.1 Hz to 1 Hz.
22. The temperature-monitored electrochemical system of claim 14 , wherein step (e) comprises calculating the Fourier transform of said impulse response to obtain said state-of-charge.
23. The temperature-monitored electrochemical system of claim 14 , wherein step (e) comprises calculating said state-of-charge based on an initial open-circuit voltage and Coulomb counting.
24. The temperature-monitored electrochemical system of claim 14 , wherein said temperature-impedance-state-of-charge relationship is in the form of an empirical look-up table or graph that is applicable to said electrochemical device or a theoretical equation correlating impedance with temperature and state-of-charge.