Circuitry for measurement of electrochemical cells

1 . Circuitry for monitoring a characteristic of a battery cell integrated into a wearable device, the circuitry configured to:

upon installation of the battery cell into the wearable device:

obtaining a first signal from the battery cell; and

upon activation of the wearable device after installation of the battery cell:

obtain a second signal from the battery cell; and

determine a characteristic of the battery cell based on the first signal and the second signal.

2 . Circuitry of claim 1 , wherein activation of the wearable device comprises powering up the wearable device.

3 . Circuitry of claim 2 , wherein the wearable device comprises a sensor for detecting removal of the wearable device from packaging, and wherein activation of the wearable device comprises removal of the wearable device from packaging.

4 . Circuitry of claim 1 , wherein the characteristic comprises one of the following:

a) a state of health;

b) a state of charge;

c) a power fade;

d) a capacity fade; and

e) ageing.

5 . Circuitry of claim 1 , wherein the circuitry is configured to:

determine a difference between the first signal and the second signal; and

determine the characteristic of the battery cell based on the difference.

6 . Circuitry of claim 5 , wherein the circuitry is configured to:

compare the difference to a difference threshold; and

determine that the characteristic is outside of a standard operating condition of the cell if the difference is greater than a difference threshold.

7 . Circuitry of claim 1 , wherein the circuitry is configured to:

compare the first signal to a first criteria;

compare the second signal to a second criteria; and

flag that the characteristic is outside of an operating range if the first signal fails to satisfy the first criteria or the second signal fails to satisfy the second criteria.

8 . Circuitry of claim 7 , wherein the second criteria is dependent on a time elapsed between the installation of the battery cell and the activation of the wearable device.

9 . Circuitry of claim 1 , comprising:

a non-volatile memory, wherein the first and second signals are stored in the non-volatile memory.

10 . Circuitry of claim 9 , further comprising:

a real time clock, wherein the first and second signal are stored in the non-volatile memory with a time stamp generated using the real time clock.

11 . Circuitry of claim 1 , wherein determining the characteristic comprises determining a fault associated with the battery cell.

12 . Circuitry of claim 1 ,

wherein obtaining the first signal from the battery cell comprises applying a first stimulus to the battery cell, wherein the first signal is responsive to the first stimulus, and

wherein obtaining the second signal from the battery cell comprises applying a second stimulus to the battery cell, wherein the second signal is responsive to the second stimulus.

13 . Circuitry of claim 12 , wherein the first stimulus and/or the second stimulus comprises a step signal or an impulse signal.

14 . Circuitry of claim 12 , wherein the first stimulus and/or the second stimulus comprises a sine wave or a triangle wave or a chirp.

15 . Circuitry of claim 14 , wherein a frequency of the sine wave or the triangle wave is adjusted over a range of frequencies.

16 . Circuitry of claim 1 , wherein determining the characteristic of the battery cell based on the first signal and the second signal comprises:

determining, from the first signal, a first impedance of the battery cell at a first frequency;

determining, from the second signal, a second impedance of the battery cell at the first frequency.

17 . Circuitry of claim 16 , wherein:

the first impedance comprises a first real component and a first imaginary component;

the second impedance comprises a second real component and a second imaginary component; and

determining the characteristic of the battery cell based on the first signal and the second signal comprises:

normalising the first impedance to obtain a first dimensionless parameter based on the first real component and the first imaginary component; and

normalising the second impedance to obtain a second dimensionless parameter based on the second real component and the second imaginary component.

18 . Circuitry of claim 17 , wherein the first dimensionless parameter is defined by a ratio of the first real component or the first imaginary component to a sum or difference of the first real and imaginary components, and/or wherein the second dimensionless parameter is defined by a ratio of the second real component or the second imaginary component to a sum or difference of the second real and imaginary components.

19 . Circuitry of claim 17 , wherein the first dimensionless parameter and the second dimensionless parameter are substantially independent of an area of an electrode of the battery cell or a distance between two or more electrodes of the battery cell.

20 . Circuitry of claim 17 , wherein determining the characteristic of the battery cell comprises comparing the first dimensionless parameter to the second dimensionless parameter.

21 . Circuitry of claim 17 , wherein the first frequency is selected to minimise a dependence of the first and second impedances on temperature.

22 . Circuitry of claim 16 , further configured to:

prior to obtaining the first signal:

apply a broadband stimulus to the battery cell;

measure a broadband response of the battery cell to the broadband stimulus over a frequency range; and

determine the first frequency based on the measured broadband response.

23 . Circuitry of claim 22 , wherein the broadband stimulus has a frequency range spanning between approximately 0.1 Hz and 1 MHz.

24 . Circuitry of claim 1 , further comprising a temperature sensor configured to monitor a temperature at the wearable device between the installation and the activation, wherein the circuitry is configured to output a temperature flag if the temperature falls outside of a safe operating range.

25 . Circuitry of claim 1 , wherein the circuitry comprises a real time clock.

26 . Circuitry of claim 25 , wherein the real time clock is configured to track a time between the installation and the activation.

27 . Circuitry of claim 25 , wherein the circuitry is configured to output a time flag if the time between the installation and the activation exceeds a predetermined duration.

28 . An integrated circuit (IC), comprising the circuitry of claim 1 .

29 . A wearable device, comprising:

circuitry of claim 1 ; and

the battery cell.

30 . The wearable device of claim 29 , wherein the wearable device comprises one of an analyte monitor, a glucose monitor, a battery monitor, a mobile computing device, a smart watch, a remote control device, a home automation controller, an audio player, a video player, a mobile telephone, and a smartphone.

31 . Circuitry for determining a state of health of an battery cell integrated into a wearable device, the circuitry configured to:

apply a first stimulus to the battery cell;

measure a first response of the battery cell to the first stimulus at a first frequency;

determine, from the first response, a first impedance of the battery cell at a first frequency, the first impedance comprising a first real component and a first imaginary component; and

normalise the first impedance to obtain a first dimensionless parameter based on the first real component and the first imaginary component; and

determine the state of health based on the first dimensionless parameter.

32 . Circuitry of claim 31 , wherein the circuitry is further configured to:

apply a second stimulus to the battery cell after application of the first stimulus;

measure a second response of the battery cell to the second stimulus at the first frequency;

determine, from the second response, a second impedance of the battery cell at a first frequency, the first impedance comprising a second real component and a second imaginary component;

normalise the second impedance to obtain a second dimensionless parameter based on the second real component and the second imaginary component; and

determine the state of health based on the second dimensionless parameter.

33 . Circuitry of claim 31 , wherein determining the state of health comprises:

comparing the first dimensionless parameter to the second dimensionless parameter.

34 . Circuitry of claim 31 , wherein the first stimulus is applied to the battery cell upon installation of the battery cell into the wearable device, and wherein the second stimulus is applied to the battery cell upon first activation of the wearable device after integration of the battery cell.