Method and circuitry to calculate the state of charge of a battery/cell

1. A method to determine a state of charge of a battery, wherein the battery includes at least two terminals, the method comprising:

determining a first indicator of a state of health of the battery during a first charge cycle;

correlating the first indicator of the state of health of the battery to a first relationship of an open circuit voltage to an amount of charge in the battery;

measuring a voltage at the terminals of the battery;

calculating an open circuit voltage of the battery using the voltage measured at the terminals of the battery, a current applied to or removed from the battery and an impedance of the battery; and

determining a first state of charge of the battery using (i) the calculated open circuit voltage and (ii) the first relationship of the open circuit voltage to the amount of charge in the battery.

2. The method of claim 1 wherein the first indicator of a state of health of the battery includes a partial relaxation time of the battery.

3. The method of claim 2 further including:

applying a current signal to the terminals of the battery, wherein the current signal includes at least one pulse;

measuring a voltage at the terminals of the battery in response to the current signal;

determining data which is representative of the partial relaxation time of the battery, wherein the relaxation time is an amount of time between (i) a time corresponding to (a) an end of the at least one pulse of the current signal and/or (b) a peak of a change in the voltage at the terminals of the battery due to the at least one pulse of the current signal and (ii) a time corresponding to when the voltage at the terminals of the battery/cell decays to at least a predetermined voltage.

4. The method of claim 1 wherein the first relationship of an open circuit voltage to the amount of charge in the battery includes data which is representative of (i) an amount of charge stored in the battery and (ii) a maximum amount of charge that is capable of being stored in the battery.

5. The method of claim 1 further including calculating the impedance of the battery.

6. The method of claim 1 further including determining a second state of charge of the battery using the first state of charge of the battery and data which is representative of an amount of charge applied to the battery during the first charge cycle.

7. The method of claim 6 further including:

outputting the data which is representative of the second state of charge of the battery; and

displaying the data which is representative of the second state of charge of the battery.

8. The method of claim 1 wherein the first indicator of a state of health of the battery is a full relaxation time or overpotential.

9. The method of claim 1 wherein the first indicator of a state of health of the battery is a peak amplitude of the voltage change.

10. The method of claim 1 further including:

determining a second indicator of a state of health of the battery during a second charge cycle;

correlating the second indicator of the state of health of the battery to a second relationship of an open circuit voltage to an amount of charge in the battery;

measuring a voltage at the terminals of the battery;

calculating an open circuit voltage of the battery using the voltage measured at the terminals of the battery, a current applied to or removed from the battery and an impedance of the battery; and

determining a second state of charge of the battery using (i) the calculated open circuit voltage and (ii) the second relationship of the open circuit voltage to the amount of charge in the battery.

11. An apparatus to determine a state of charge of a battery, wherein the battery includes at least two terminals, the apparatus comprising:

signal generation circuitry, coupled to the battery, to generate a signal and apply the signal to the terminals of the battery, wherein the signal includes at least one pulse;

measurement circuitry, coupled to the battery, to measure a terminal voltage of the battery in response to the pulse; and

control circuitry, coupled to the measurement circuitry, wherein the control circuitry is configured to:

determine data which is indicative of a state of health of the battery using the terminal voltage of the battery in response to the pulse;

determine a relationship of an open circuit voltage to an amount of charge in the battery using the data which is indicative of a state of health of the battery;

calculate an open circuit voltage of the battery using the voltage measured at the terminals of the battery, a current applied to or removed from the battery and an impedance of the battery; and

determine a state of charge of the battery using (i) the calculated open circuit voltage and (ii) the relationship of the open circuit voltage to the amount of charge in the battery.

12. The apparatus of claim 11 wherein the relationship of the open circuit voltage to the amount of charge in the battery includes data which is representative of (i) an amount of charge stored in the battery and (ii) a maximum amount of charge that is capable of being stored in the battery.

13. The apparatus of claim 11 wherein the data which is indicative of a state of health of the battery includes a partial relaxation time of the battery.

14. The apparatus of claim 11 wherein the relationship of the open circuit voltage to the amount of charge in the battery includes data which is representative of (i) an amount of charge stored in the battery and (ii) a maximum amount of charge that is capable of being stored in the battery.

15. The apparatus of claim 11 wherein the data which is indicative of a state of health of the battery includes a peak amplitude of the voltage change in response to a charge pulse and/or full relaxation time or overpotential.

16. A method to calculate and output a state of charge of a battery, wherein the battery includes at least two terminals, the method comprising:

applying a current pulse to the terminals of the battery during a charge cycle;

measuring a voltage at the terminals of the battery in response to the current pulse;

determining data which is indicative of a state of health of the battery using the voltage at the terminals of the battery;

determining a relationship of an open circuit voltage to an amount of charge in the battery using the data which is representative of the state of health of the battery;

calculating an open circuit voltage of the battery using the voltage measured at the terminals of the battery, a current applied to or removed from the battery and an impedance of the battery; and

determining a state of charge of the battery using (i) the calculated open circuit voltage and (ii) the relationship of the open circuit voltage to the amount of charge in the battery.

17. The method of claim 16 wherein the data which is indicative of a state of health of the battery includes a partial relaxation time of the battery.

18. The method of claim 17 further including:

measuring a voltage at the terminals of the battery in response to the charge pulse;

determining data which is representative of the partial relaxation time of the battery, wherein the relaxation time is an amount of time between (i) a time corresponding to an end of the pulse of a charge packet of the charge signal and (ii) a time corresponding to when the voltage at the terminals of the battery/cell decays to at least a predetermined voltage.

19. The method of claim 16 wherein the relationship of the open circuit voltage to the amount of charge includes data which is representative of (i) an amount of charge stored in the battery and (ii) a maximum amount of charge that is capable of being stored in the battery.

20. The method of claim 16 further including determining a second state of charge of the battery using the state of charge and data which is representative of the amount of charge applied to the battery during the charge cycle.

21. The method of claim 20 further including:

outputting the data which is representative of the second state of charge of the battery; and

displaying the data which is representative of the second state of charge of the battery.

22. The method of claim 16 wherein the data which is indicative of a state of health of the battery includes a full relaxation time or overpotential.

23. The method of claim 16 wherein the data which is indicative of a state of health of the battery includes a peak amplitude of the voltage change.