Method and apparatus for charging batteries at reduced overcharge levels

• US 6,456,042 B1
• Filed: 11/27/2000
• Issued: 09/24/2002
• Est. Priority Date: 11/27/2000
• Status: Expired due to Term

• Current Assignee: Dynavair LLC (IP Edge LLC)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Kwok, Wellington Y.
• Primary Examiner(s): Tso, Edward H.
• Assistant Examiner(s): LUK, LAWRENCE W
• Application Number:
  US09/722,941
• Time in Patent Office: 666 Days
• Field of Search: 320/134, 320/128, 320/157, 320/159, 320/162, 320/164, 324/430, 324/431
• US Class Current: 320/134
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/00711 with introduction of pulses during the charging process

Abstract

Battery charging methods and associated chargers which are capable of rapidly charging a battery while subjecting it to reduced levels of overcharging. The methods described are capable of being utilized within numerous battery charging systems for batteries spanning a range of chemistries, such as lead-acid, nickel-based, and lithium-based batteries. Upon detection of the onset-of-overcharge during the charge process, a variable voltage lid is imposed (V_LID=ν(φ)+βlogφ+κφ) which reduces the maximum voltage that may be applied to the battery as a function of charge acceptance which is typically estimated by a calculation based on state-of-charge. Additionally, the voltage lid can be approximated with step-wise voltage lids which are responsive to the level of charge acceptance within the battery.

Claims

1. A method of charging a battery, comprising:

(a) applying a controlled level of current to the battery; and

(b) modulating current applied to the battery wherein the resultant charge voltage applied to the battery is downwardly modulated in response to an onset-of-overcharging condition and wherein the amount of overcharging potential to which the battery is subjected is limited.

2. A method of charging a battery, comprising:

(a) supplying a charging current to a battery;

(b) detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and

(c) decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited.

3. A method as recited in claim 2, further comprising supplying charge current to the battery from a controllable current source that forces current through a series resistance, said series resistance comprising the current source and the battery being charged.

4. A method as recited in claim 2, further comprising supplying the charge current to the battery at a constant rate and limiting the charger current by a maximum voltage lid.

5. A method as recited in claim 2, further comprising providing a stepwise current output that controlled according to the voltage lid.

6. A method as recited in claim 2, further comprising detecting the onset-of-overcharge at a predetermined level of SOC in relation to the applied current.

7. A method as recited in claim 6, further comprising empirically determining a relationship between the onset-of-overcharge and the SOC as a function of applied current and temperature.

8. A method as recited in claim 2, further comprising detecting the level of outgassing of the battery and determining the onset-of-overcharge by the level of detected outgassing.

9. A method as recited in claim 2, wherein the voltage lid is a function of battery state-of-charge given by V_LID=ν

(φ

)+β

logφ

+κ

φ

.

10. A method as recited in claim 9, further comprising approximating the voltage lid by a series of discrete steps having a step size determined by the degree of matching required by the level of overcharging to be allowed within a particular application.

11. A method as recited in claim 10, further comprising providing at least three steps in which maximum fixed voltages are applied to battery charging, the three steps being defined within an associated three ranges of state-of-charge.

12. A method as recited in claim 2, further comprising approximating the voltage lid by functions representing similar response profiles which decrease as the state-of-charge progresses, and determining a degree of function matching by the level of overcharging to be allowed within a particular application.

13. A method as recited in claim 2, further comprising determining the voltage lid by reaching a normalized maximum gassing rate attained during charging of the battery.

14. A method as recited in claim 13, further comprising setting the normalized maximum gassing rate to approximately 1.0 SCCM/A during charging.

15. A method as recited in claim 2, further comprising determining the voltage lid by reaching a constant voltage gradient dV/dQ wherein the voltage per ampere-hour exceeds a specified threshold during charging of the battery.

16. A method as recited in claim 2, further comprising charging a battery selected from the group of batteries consisting of lead-acid, nickel-cadmium, nickel-metal-hydride, lithium-ion, nickel-based, and lithium-based.

17. A method as recited in claim 2, further comprising applying a high battery charging rate exceeding 1.2C to a battery whose state-of-charge is sufficiently low as not to be subject to an onset-of-overcharge condition which allows initial charging to proceed rapidly.

18. A method of charging a battery, comprising the steps of:

(a) applying charging current to the battery at a controlled level limited by a voltage lid;

(b) detecting an onset-of-overcharge condition while charging at the existing level of charge current;

(c) reducing the voltage lid as a result of the detected onset-of-overcharge condition to limit the current applied to the battery and the overcharge potential; and

(d) repeating steps (b) and (c) until the applied current to the battery has been limited to a sufficiently low level to constitute a desired “

float charge”

.

19. A method as recited in claim 18, further comprising estimating the onset-of-overcharge condition detection according to the conditions of SOC, applied current and temperature.

20. A method as recited in claim 18, further comprising detecting outgassing of the battery and determining the onset-of-overcharge condition by the level of detected outgassing which occurs.

21. A method as recited in claim 18, further comprising providing a stepwise current output that is controlled according to the voltage lid.

22. An apparatus for charging a battery, comprising:

(a) means for applying a controlled level of current to the battery; and

(b) means for modulating current applied to the battery wherein the resultant charge voltage applied to the battery is downwardly modulated in response to an onset-of-overcharging condition and wherein the amount of overcharging potential to which the battery is subjected is limited.

23. An apparatus for charging a battery, comprising:

(a) means for supplying a charging current to a battery;

(b) means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and

(c) means for decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected.

24. An apparatus as recited in claim 23, wherein the charge current is supplied to the battery from a controllable current source that forces current through a series resistance, said series resistance comprising the voltage source and the battery being charged.

25. An apparatus as recited in claim 23, wherein the charge current is supplied to the battery at a constant rate and is limited by a maximum voltage lid.

26. An apparatus as recited in claim 23, further comprising means for providing stepwise current output controlled according to the voltage lid.

27. An apparatus as recited in claim 23, wherein the onset-of-overcharge is detected at a predetermined level of SOC in relation to the applied current.

28. An apparatus as recited in claim 27, wherein an empirical relationship between the onset-of-overcharge and the SOC is empirically determined in relation to parameters comprising applied current and temperature.

29. An apparatus as recited in claim 23, further comprising means for detecting outgassing of the battery and wherein the onset-of-overcharge is determined by the level of detected outgassing.

30. An apparatus as recited in claim 23, wherein the voltage lid is a function of battery state-of-charge given by V_LID=ν

(φ

)+β

logφ

+κ

φ

.

31. An apparatus as recited in claim 30, wherein the voltage lid is approximated by a series of discrete steps having a step size determined by a degree of matching required by the level of overcharging to be allowed within a particular application.

32. An apparatus as recited in claim 31, wherein at least three steps are provided in which maximum fixed voltages are applied to battery charging, the three steps being defined within an associated three ranges of state-of-charge.

33. An apparatus as recited in claim 23, wherein the voltage lid is approximated by functions representing similar response profiles which decrease as the state-of-charge progresses, with a degree of function matching being determined by the level of overcharging to be allowed within a particular application.

34. An apparatus as recited in claim 23, wherein the voltage lid is determined by reaching a normalized maximum gassing rate attained during charging of the battery.

35. An apparatus as recited in claim 34, wherein the normalized maximum gassing rate is set to approximately 1.0 SCCM/A during charging.

36. An apparatus as recited in claim 23, wherein the voltage lid is determined by reaching a constant voltage gradient dV/dQ wherein the voltage per ampere-hour exceeds a specified threshold during charging of the battery.

37. An apparatus as recited in claim 23, wherein the battery charges is selected from the group of batteries consisting of lead-acid, nickel-cadmium, nickel-metal-hydride, lithium-ion, nickel-based, and lithium-based.

38. An apparatus as recited in claim 23, wherein said apparatus is configured for a high battery charging rate exceeding 1.2C for a battery whose state-of-charge is sufficiently low as not to be subject to an onset-of-overcharge condition which allows initial charging to proceed rapidly.

39. An apparatus for charging a battery, comprising:

(a) means for applying charging current to the battery at a controlled level limited by a voltage lid;

(b) means for detecting an onset-of-overcharge condition while charging at the existing level of charge current;

(c) means for reducing the voltage lid as a result of the detected onset-of-overcharge condition to limit the current applied to the battery and the overcharge potential; and

(d) means for limiting the applied current to the battery to a sufficiently low level to constitute a desired “

float charge”

.

40. An apparatus as recited in claim 39, wherein the onset-of-overcharge condition detection is estimated according to the conditions of SOC, applied current and temperature.

41. An apparatus as recited in claim 39, further comprising means for detecting outgassing of the battery, and wherein the onset-of-overcharge condition is determined by the level of detected outgassing which occurs.

42. An apparatus as recited in claim 39, further comprising means for providing stepwise current output controlled according to the voltage lid.

43. A method of charging a battery, comprising:

supplying a charging current to a battery from a controllable current source that forces current through a series resistance, said series resistance comprising the current source and the battery being charged;

detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and

decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited.

44. A method of charging a battery, comprising:

supplying a charging current to a battery;

detecting an onset-of-overcharge condition as the battery is supplied with said charging current;

decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited; and

wherein charge current is supplied to the battery at a constant rate which is limited by a maximum set by said voltage lid.

45. A method of charging a battery, comprising:

supplying a charging current to a battery;

detecting an onset-of-overcharge condition as the battery is supplied with said charging current;

decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited; and

wherein a stepwise current output is provided which is controlled according to said voltage lid.

46. A method of charging a battery, comprising:

supplying a charging current to a battery;

detecting an onset-of-overcharge condition as the battery is supplied with said charging current;

decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited; and

detecting the level of outgassing of the battery and determining the onset-of-overcharge by the level of detected outgassing.

47. A method of charging a battery, comprising:

supplying a charging current to a battery;

detecting an onset-of-overcharge condition as the battery is supplied with said charging current;

decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited; and

wherein said voltage lid is a function of battery state-of-charge given by V_LID=ν

φ

+β

logφ

+κ

φ

.

48. A method as recited in claim 47, further comprising setting the normalized maximum gassing rate to approximately 1.0 SCCM/A during charging.

49. A method as recited in claim 48, further comprising providing at least three steps in which maximum fixed voltages are applied to battery charging, the three steps being defined within an associated three ranges of state-of-charge.

50. A method of charging a battery, comprising:

supplying a charging current to a battery;

detecting an onset-of-overcharge condition as the battery is supplied with said charging current;

decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited; and

approximating the voltage lid by functions representing similar response profiles which decrease as the state-of-charge progresses, and determining a degree of function matching by the level of overcharging to be allowed within a particular application.

51. A method of charging a battery, comprising:

supplying a charging current to a battery;

detecting an onset-of-overcharge condition as the battery is supplied with said charging current;

decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited; and

determining said voltage lid by reaching a normalized maximum gassing rate attained during charging of the battery.

52. A method as recited in claim 51, further comprising setting the normalized maximum gassing rate to approximately 1.0 SCCM/A during charging.

53. A method of charging a battery, comprising:

supplying a charging current to a battery;

detecting an onset-of-overcharge condition as the battery is supplied with said charging current;

decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited; and

determining said voltage lid by reaching a constant voltage gradient dV/dQ wherein the voltage per ampere-hour exceeds a specified threshold during charging of the battery.

54. A method of charging a battery, comprising:

supplying a charging current to a battery;

detecting an onset-of-overcharge condition as the battery is supplied with said charging current;

decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, and wherein the overcharge potentials to which the battery is subjected are limited; and

wherein said charging current is supplied as a high charging rate exceeding 1.2C to said battery when its state-of-charge is sufficiently low as not to be subject to an onset-of-overcharge condition which allows initial charging to proceed rapidly.

55. A method of charging a battery, comprising the steps of:

applying a stepwise charging current output to the battery at a controlled level limited according to a voltage lid;

detecting an onset-of-overcharge condition while charging at the existing level of charge current;

reducing the voltage lid as a result of the detected onset-of-overcharge condition to limit the current applied to the battery and the overcharge potential; and

repeating the above two steps until the applied current to the battery has been limited to a sufficiently low level to constitute a desired “

float charge”

.

56. An apparatus for charging a battery, comprising:

means for supplying a charging current to a battery from a controllable current source that forces current through a series resistance, said series resistance comprising the voltage source and the battery being charged;

means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and

means for decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected.

57. An apparatus for charging a battery, comprising:

means for supplying a charging current to a battery at a constant rate which is limited by a maximum voltage lid;

means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and

means for decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected.

58. An apparatus for charging a battery, comprising:

means for supplying a charging current to a battery as a stepwise current output controlled according to the voltage lid;

means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and

means for decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected.

59. An apparatus for charging a battery, comprising:

means for supplying a charging current to a battery;

means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current;

means for decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition, wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected; and

means for detecting outgassing of the battery and wherein the onset-of-overcharge is determined by the level of detected outgassing.

60. An apparatus for charging a battery, comprising:

means for supplying a charging current to a battery;

means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and

means for decreasing the maximum charge voltage being applied to said battery upon detection of the onset-of-overcharge condition;

wherein said charging current is subjected to a voltage lid that decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected.

wherein the voltage lid is a function of battery state-of-charge given by V_LID=ν

φ

+β

logφ

+κ

φ

.

61. An apparatus as recited in claim 60, wherein said voltage lid is approximated by a series of discrete steps having a step size determined by a degree of matching required by the level of overcharging to be allowed within a particular application.

62. An apparatus as recited in claim 61, wherein at least three steps are provided in which maximum fixed voltages are applied to said battery charging, the three steps being defined within an associated three ranges of state-of-charge.

63. An apparatus for charging a battery, comprising:

means for supplying a charging current to a battery;

means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and

means for decreasing the maximum charge voltage being applied to said battery according to a voltage lid upon detection of the onset-of-overcharge condition;

wherein said voltage lid decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected;

wherein said voltage lid is approximated by functions representing similar response profiles which decrease as the state-of-charge progresses, with a degree of function matching being determined by the level of overcharging to be allowed within a particular application.

64. An apparatus for charging a battery, comprising:

means for supplying a charging current to a battery;

means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and

means for decreasing the maximum charge voltage being applied to said battery according to a voltage lid upon detection of the onset-of-overcharge condition;

wherein said voltage lid decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected;

wherein the voltage lid is determined by reaching a normalized maximum gassing rate attained during charging of the battery.

65. An apparatus as recited in claim 64, wherein said normalized maximum gassing rate is set to approximately 1.0 SCCM/A during charging.

66. An apparatus for charging a battery, comprising:

means for supplying a charging current to a battery;

means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and

means for decreasing the maximum charge voltage being applied to said battery according to a voltage lid upon detection of the onset-of-overcharge condition;

wherein said voltage lid decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected;

wherein said voltage lid is determined by reaching a constant voltage gradient dV/dQ wherein the voltage per ampere-hour exceeds a specified threshold during said charging of the battery.

67. An apparatus for charging a battery, comprising:

means for supplying a charging current to a battery;

means for detecting an onset-of-overcharge condition as the battery is supplied with said charging current; and

means for decreasing the maximum charge voltage being applied to said battery according to a voltage lid upon detection of the onset-of-overcharge condition;

wherein said voltage lid decreases as the state-of-charge progresses, so as to limit the overcharge potentials to which the battery is subjected;

wherein said apparatus is configured for a high battery charging rate exceeding 1.2C for a battery whose state-of-charge is sufficiently low as not to be subject to an onset-of-overcharge condition which allows initial charging to proceed rapidly.

68. An apparatus for charging a battery, comprising:

means for applying charging current to the battery at a controlled level limited by a voltage lid;

means for detecting an onset-of-overcharge condition while charging at the existing level of charge current;

means for reducing the voltage lid as a result of the detected onset-of-overcharge condition to limit the current applied to the battery and the overcharge potential;

means for limiting the applied current to the battery to a sufficiently low level to constitute a desired “

float charge”

; and

means for detecting outgassing of said battery, and wherein the onset-of-overcharge condition is determined by the level of detected outgassing which occurs.

69. An apparatus for charging a battery, comprising:

means for applying charging current to the battery at a controlled level limited by a voltage lid;

means for detecting an onset-of-overcharge condition while charging at the existing level of charge current;

means for reducing the voltage lid as a result of the detected onset-of-overcharge condition to limit the current applied to the battery and the overcharge potential;

means for limiting the applied current to the battery to a sufficiently low level to constitute a desired “

float charge”

; and

wherein said charging current is applied stepwise and controlled according to said voltage lid.

70. A method of charging a battery, comprising:

applying a controlled level of charge current to the battery from a controllable current source that forces current through a series resistance, said series resistance comprising the current source and the battery being charged; and

modulating current applied to the battery wherein the resultant charge voltage applied to the battery is downwardly modulated in response to an onset-of-overcharging condition and wherein the amount of overcharging potential to which the battery is subjected is limited.

71. An apparatus for charging a battery, comprising:

means for applying a controlled level of current to the battery;

wherein said controlled level of current is applied through a series resistance, said series resistance comprising the voltage source and the battery being charged; and

means for modulating current applied to the battery wherein the resultant charge voltage applied to the battery is downwardly modulated in response to an onset-of-overcharging condition and wherein the amount of overcharging potential to which the battery is subjected is limited.