Charging regime at any state of charge using the first derivative of temperature and the first and second derivative of voltage with respect to time

• US 20080164849A1
• Filed: 01/09/2007
• Published: 07/10/2008
• Est. Priority Date: 01/09/2007
• Status: Abandoned Application

• Current Assignee: Chevron Technology Ventures LLC (Chevron Corp.)
• Original Assignee: Cobasys LLC (Robert Bosch GmbH)
• Inventors: Ciaramitaro, Christopher M.
• Application Number:
  US11/651,129
• Publication Number:
  US 20080164849A1
• Time in Patent Office: Days
• US Class Current: 320/151
• CPC Class Codes: H01M 10/345 Gastight metal hydride accumulators
• CPC Class Codes: H01M 10/425 Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing printed circuits H05K1/00
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/443 in response to temperature
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/007184 in response to battery voltage gradient
• CPC Class Codes: H02J 7/007194 of the battery
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A battery control module for a rechargeable battery includes a voltage measuring module that measures a voltage of the rechargeable battery and that estimates a first derivative of the voltage with respect to time (dV/dt) and a second derivative of the voltage with respect to time (d²V/dt²). A charge control module estimates a maximum charging current based on dV/dt. A current control module limits a charging current of the rechargeable battery to the maximum charging current and turns off the charging current when d²V/dt² is greater than dV/dt.

Claims

1. A battery control module for a rechargeable battery, comprising:

a voltage measuring module that measures a voltage of the rechargeable battery and that estimates a first derivative of the voltage with respect to time (dV/dt) and a second derivative of the voltage with respect to time (d²V/dt²);

a charge control module that estimates a maximum charging current based on dV/dt; and

a current control module that limits a charging current of the rechargeable battery to the maximum charging current and that turns off the maximum charging current when d²V/dt² is greater than dV/dt.

2. The battery control module of claim 1 further comprising a temperature measuring module that measures a temperature of the battery and that estimates a first derivative of the battery temperature with respect to time (dT/dt), wherein the current control module turns off the charging current when dT/dt is greater than a predetermined rate.

3. The battery control module of claim 1 wherein the charge control module sets the maximum charging current to a predetermined value when dV/dt is greater than a first predetermined value.

4. The battery control module of claim 3 wherein the charge control module sets the maximum charging current to the predetermined value divided by s when dV/dt is less than the first predetermined value, wherein s is a rational number greater than 1.

5. The battery control module of claim 4 wherein the charge control module sets the maximum charging current to the predetermined value divided by r when dV/dt is less than a second predetermined value, wherein r is a rational number greater than s and the first predetermined value is greater than the second predetermined value.

6. The battery control module of claim 5 wherein r=5 and s=2.

7. A rechargeable battery system comprising the battery control module of claim 1 and the rechargeable battery.

8. The rechargeable battery system of claim 7 wherein the rechargeable battery is a nickel metal hydride battery.

9. A battery control module for a rechargeable battery, comprising:

a voltage measuring module that measures a voltage of the rechargeable battery and that estimates a first derivative of the voltage with respect to time (dV/dt);

a charge control module that estimates a maximum charging current based on dV/dt;

a temperature measuring module that measures a temperature of the battery, estimates a first derivative of the battery temperature with respect to time (dT/dt), and communicates with the charge control module; and

a current control module that limits a charging current of the rechargeable battery to the maximum charging current and that reduces the maximum charging current from an initial value while dT/dt is less than a predetermined rate and dV/dt is positive and decreasing.

10. The battery control module of claim 9 wherein the current control module sets the maximum charging current to substantially zero when dT/dt is greater than a predetermined rate.

11. The battery control module of claim 9 wherein the control module steps the maximum charging current down from an initial value to a first value, and down from a first value to a second value.

12. The battery control module of claim 11 wherein the first value is one-half of the initial value and the second value is one-fifth of the initial value.

13. The battery control module of claim 9 wherein the voltage measuring module estimates a second derivative of the voltage with respect to time (d²V/dt²) and wherein the current control module turns off the charging current when d²V/dt² is greater than dV/dt.

14. A rechargeable battery system comprising the battery control module of claim 9 and the rechargeable battery.

15. The rechargeable battery system of claim 14 wherein the rechargeable battery is a nickel metal hydride battery.

16. A method of recharging a rechargeable battery, comprising:

measuring a voltage of the rechargeable battery;

estimating a first derivative of the voltage with respect to time (dV/dt) and a second derivative of the voltage with respect to time (d²V/dt²);

establishing a charging current limit based on dV/dt;

limiting a charging current of the rechargeable battery to the charging current limit; and

turning off the charging current when d²V/dt² is greater than dV/dt.

17. The method of claim 16 further comprising:

measuring a temperature of the battery;

estimating a first derivative of the battery temperature with respect to time (dT/dt); and

turning off the charging current when dT/dt is greater than a predetermined rate.

18. The method of claim 16 further comprising setting the charging current limit to a predetermined value when dV/dt is greater than a first predetermined value.

19. The method of claim 18 further comprising setting the charging current limit to the predetermined value divided by s when dV/dt is less than a first predetermined value, wherein s is a rational number greater than 1.

20. The method of claim 19 further comprising setting the charging current limit to the predetermined value divided by r when dV/dt is less than a second predetermined value, wherein r is a rational number greater than s and the first predetermined value is greater than the second predetermined value.

21. A method of charging a rechargeable battery, comprising:

measuring a voltage of the rechargeable battery;

estimating a first derivative of the voltage with respect to time (dV/dt);

estimating a maximum charging current based on dV/dt;

measuring a temperature of the battery;

estimating a first derivative of the battery temperature with respect to time (dT/dt);

limiting a charging current of the rechargeable battery to the maximum charging current;

reducing the maximum charging current from an initial value while dT/dt is less than a predetermined rate and dV/dt is positive and decreasing.

22. The method of claim 21 further comprising turning off the charging current when dT/dt is greater than a predetermined rate.

23. The method of claim 21 further comprising stepping the maximum charging current down from an initial value to a first value, and down from a first value to a second value.

24. The method of claim 23 wherein the first value is one-half of the initial value and the second value is one-fifth of the initial value.

25. The method of claim 21 further comprising estimating a second derivative of the voltage with respect to time (d²V/dt²) and turning off the charging current when d²V/dt² is greater than dV/dt.