Apparatus and method for step-charging batteries to optimize charge acceptance

• US 5,589,757 A
• Filed: 06/07/1995
• Issued: 12/31/1996
• Est. Priority Date: 01/26/1994
• Status: Expired due to Term

• Current Assignee: Midtronics Incorporated
• Original Assignee: GNB Battery Technologies, Inc.
• Inventors: Klang, James K.
• Primary Examiner(s): Nappi, Robert
• Assistant Examiner(s): Law, Patrick B.
• Application Number:
  US08/480,828
• Time in Patent Office: 573 Days
• Field of Search: 320/22, 320/23, 320/24, 320/30, 320/31, 320/32, 320/39
• US Class Current: 320/160
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H02J 7/00712 the cycle being controlled or terminated in response to electric parameters
• CPC Class Codes: Y02B 40/00 Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/13 Energy storage using capacitors

Abstract

Apparatus and method for charging a battery, wherein a charging voltage is applied to a battery. The charging voltage depends on a base charging voltage which is continually adjusted in the direction that provides a more optimal level of charge acceptance. The direction of a more optimal charge acceptance is determined by adjusting the charging voltage in steps of predetermined magnitudes such that the steps provide an upper pair and a lower pair of spaced-apart charging levels. The current at each stepped voltage is measured, and used to calculate first and second current differentials corresponding to the upper and lower pairs. The base charging level is incremented or decremented to adjust the base charging level in the direction that provided the smaller differential. As the process is repeated, the charging level continually moves closer to a charging voltage level that minimizes the differential thereby providing a more optimal charge acceptance.

Claims

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

applying an electrical charging output to the battery in dependence on a base charging level;

adjusting the charging output to provide a plurality of charging levels comprising an upper pair and a lower pair of charging levels, each of the charging levels in the upper pair distinct in magnitude from one another and each of the charging levels in the lower pair distinct in magnitude from one another;

measuring a charge input to the battery at each of the charging levels comprising the upper pair and at each of the charging levels comprising the lower pair;

calculating a lower differential from the difference in the charge inputs at the two charging levels comprising the lower pair of charging levels, and calculating an upper differential from the difference in the charge inputs at the two charging levels comprising the upper pair of charging levels

comparing the lower differential and the upper differential; and

adjusting the base charging level based on the differential comparison.

2. The method of claim 1 wherein the electrical charging output applied to the battery comprises a voltage, and the step of measuring the charge input to the battery at each charging level comprises measuring a current flow.

3. The method of claim 2 wherein the step of adjusting the base charging level based on the differential comparison comprises the step of increasing the base voltage a selected increment amount if the lower differential is greater than the upper differential by a selected amount, or decreasing the base voltage a selected decrement amount if the lower differential is less than the upper differential by a selected amount.

4. The method of claim 2 wherein the step of adjusting the charging output includes the step of increasing the applied voltage a selected step amount to a plurality of levels that provide the lower pair and the upper pair of spaced-apart charging levels.

5. The method of claim 4 further comprising the step of decreasing the applied voltage a selected amount before the step of increasing the voltage to the plurality of levels.

6. The method of claim 2 wherein the step of adjusting the charging output includes the step of decreasing the applied voltage a selected step amount to a plurality of levels that provide the upper pair and the lower pair of spaced-apart charging levels.

7. The method of claim 6 further comprising the step of increasing the applied voltage a selected amount before the step of decreasing the voltage to the plurality of levels.

8. The method of claim 1 wherein the charging output is adjusted such than one of the charging levels of the upper pair of spaced-apart charging levels is common to one of the charging levels of the lower pair.

9. The method of claim 1 wherein the step of measuring the charge input to the battery at each charging level further comprises the step of delaying an amount of time before measuring the charge input to the battery, wherein each charging level measured has a delay time corresponding thereto.

10. The method of claim 1 further comprising the steps of determining whether the battery has achieved a desired amount of charge, and terminating the application of the electrical charging output when the battery has achieved the desired amount.

11. The method of claim 10 further comprising the step of entering a maintenance mode when the battery has achieved the desired amount of charge.

12. The method of claim 11 wherein the step of entering a maintenance mode comprises the step of controlling the power supply to apply a predetermined output level to charging terminals of the battery.

13. The method of claim 11 further comprising the step of connecting a resistive load across the charging terminals of the battery.

14. The method of claim 1 further comprising the steps of determining whether the battery has achieved a desired amount of charge, and providing an increased output charging level to the battery for a period of time to condition the battery including destratifying the battery electrolyte when the desired amount has been achieved.

15. The method of claim 1 wherein the electrical charging output applied to the battery comprises a current, and the step of measuring the charge input to the battery at each charging level comprises measuring a voltage.

16. The method of claim 15 wherein the step of adjusting the base charging level based on the differential comparison comprises the step of increasing the base current a selected increment amount if the lower differential is less than the upper differential by a selected amount, or decreasing the base current a selected decrement amount if the lower differential is greater than the upper differential by a selected amount.

17. The method of claim 1 wherein the steps of applying an electrical charging output, adjusting the charging output to provide upper and lower pairs, measuring the charge input at each of the charging levels, calculating a lower differential and an upper differential, comparing the lower differential and the upper differential and adjusting the base charging level based on the differential comparison are continually repeated.

18. The method of claim 1 wherein the steps of applying an electrical charging output, adjusting the charging output to provide upper and lower pairs, measuring the charge input at each of the charging levels, calculating a lower differential and an upper differential, comparing the lower differential and the upper differential and adjusting the base charging level based on the differential comparison are repeated after a delay time.

19. An apparatus for charging a battery, comprising:

a controllable power source providing an electrical charging output at variable current or voltage levels;

means for connecting the power source to charging terminals of the battery;

control circuitry for controlling the power source to apply the electrical charging output to the battery at a plurality of levels with respect to a base charging level, including charging output levels comprising an upper pair and a lower pair of spaced-apart charging levels;

a sensor for measuring charging input to the battery at each charging level comprising one of said pairs and providing charging input values corresponding thereto;

arithmetic means for calculating a lower differential from the difference in the charge inputs at the two charging levels comprising the lower pair of charging levels, and for calculating an upper differential from the difference in the charge inputs at the two charging levels comprising the upper pair of charging levels; and

comparison circuitry for comparing the lower and upper differentials with one another and providing a comparison result, the comparison circuitry being operatively connected to provide the comparison result to the control circuitry, the control circuitry increasing or decreasing the base charging level in dependence on the comparison result.

20. The apparatus of claim 19 wherein the control circuitry controls the power source to apply a voltage to the battery, whereby the base charging level is a base voltage level, and the sensor comprises a current sensor for measuring current levels indicative of the charging input to the battery at each charging level comprising one of said pairs.

21. The apparatus of claim 20 wherein the control circuitry increases the base voltage level a selected increment amount if the lower current differential is greater than the upper current differential by a selected amount, and decreases the base voltage level a selected decrement amount if the lower current differential is less than the upper current differential by a selected amount.

22. The apparatus of claim 19 further comprising means for selectively connecting a resistor across the charging terminals of the battery.

23. The apparatus of claim 19 wherein the control circuitry, arithmetic means and comparison circuitry include a microprocessor, and wherein the sensor includes an analog-to-digital voltage converter.

24. The apparatus of claim 19 further including timing circuitry for delaying a selected amount of time before the sensor measures the charge input to the battery, each charging output level comprising one of said pairs having a delay time corresponding thereto.

25. The apparatus of claim 24 wherein the charging output levels stabilize with time, and wherein the delay times provided by the timing circuitry influence the charging input levels measured by the sensor.

26. The apparatus of claim 19 wherein the control circuitry controls the charging output such that one of the charging levels of the upper pair of spaced-apart charging levels is common to one of the charging levels of the lower pair.

27. The apparatus of claim 19 wherein the control circuitry controls the power source to apply voltage to the battery in increasing voltage levels over time to provide the lower and upper pairs of spaced-apart charging levels.

28. The apparatus of claim 27 wherein the control circuitry controls the power source such that the voltage is increased in discrete steps.

29. The apparatus of claim 27 wherein the control circuitry controls the power source to apply voltage to the battery at a lowered level for a period of time before applying voltage to the battery in increasing voltage levels over time.

30. The apparatus of claim 19 wherein the control circuitry controls the power source to apply voltage to the battery in decreasing levels over time to provide the upper and lower pairs of spaced-apart charging levels.

31. The apparatus of claim 30 wherein the control circuitry controls the power source such that the voltage is decreased in discrete steps.

32. The apparatus of claim 30 wherein the control circuitry controls the power source to apply voltage to the battery a an increased level for a period of time before decreasing the levels to the upper and lower pairs of spaced-apart charging levels.

33. The apparatus of claim 19 further comprising means for determining when the battery has achieved a desired level of charge.

34. The apparatus of claim 33 wherein the means for determining when the battery has achieved a desired level of charge includes means for detecting a substantially constant average charge input to the battery.

35. The apparatus of claim 33 further comprising means for providing an increased output charging level to the battery for a period of time to condition the battery after the battery has achieved a desired level of charge.

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

outputting a charging voltage to the battery in dependence on a base voltage level;

adjusting the charging voltage in steps of predetermined magnitudes to provide first, second and third voltage levels, wherein the first level is less than the second level and the second level is less than the third level;

measuring first, second and third currents at the first, second and third voltage levels, respectively;

calculating a first differential from the difference in the first current from the second current, and calculating a second differential from the difference in the second current from the third current;

comparing the first differential and the second differential; and

increasing the base voltage a selected increment amount if the first differential is greater than the second differential, or decreasing the base voltage a selected decrement amount if the first differential is less than the second differential.

37. The method of claim 36 wherein the step of adjusting the charging voltage to the first, second and third levels includes the step of successively increasing the charging voltage from the first level to the second level to the third level.

38. The method of claim 37 further comprising the steps of adjusting the charging voltage to a lowered level that is less than the first voltage level, and increasing the charging voltage from the lowered level to the first level.

39. The method of claim 36 wherein the steps of outputting a charging voltage, adjusting the charging voltage in steps, measuring first, second and third currents, calculating a first differential and a second differential, comparing the first differential and the second differential, and increasing the base voltage a selected increment amount if the first differential is greater than the second differential, or decreasing the base voltage a selected decrement amount if the first differential is less than the second differential, are continually repeated.

40. The method of claim 36 wherein the steps of outputting a charging voltage, adjusting the charging voltage in steps, measuring first, second and third currents, calculating a first differential and a second differential, comparing the first differential and the second differential, and increasing the base voltage a selected increment amount if the first differential is greater than the second differential, or decreasing the base voltage a selected decrement amount if the first differential is less than the second differential, are repeated after a delay time.

41. An apparatus for charging a battery, comprising:

a controllable power source providing an electrical charging output at variable current or voltage levels;

means for connecting the power source to charging terminals of the battery;

control circuitry for controlling the power source to periodically apply the electrical charging output to the battery at first, second, third and fourth output levels with respect to a base charging level;

a sensor for measuring charging input to the battery at the first, second, third and fourth output levels and providing first, second, third and fourth charging input values corresponding thereto;

means for receiving the first, second, third and fourth input values from the sensor and for determining a differential between the first and second charging input values and a differential between the third and fourth charging input values; and

comparison circuitry for comparing the differentials and providing a comparison result, the comparison circuitry further being operatively connected to the control circuitry to increase or decrease the base charging level in accordance with the comparison result.

42. The apparatus of claim 41 wherein the charging outputs are voltages and the input values are currents, and wherein the fourth charging voltage level is greater than the first charging voltage level, and the control circuitry increases the base charging level a selected increment amount if the differential between the first and second current input values is greater than the differential between the third and fourth current input values.

43. The apparatus of claim 41 wherein the control means controls the power supply to apply the electrical charging output such that the second output level equals the third output level.

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

a) applying an electrical charging output to the battery in dependence on a base charging level, b) adjusting the charging output to provide an upper pair and a lower pair of spaced-apart charging levels, c) measuring charge input to the battery at each charging level comprising one of said pairs, d) calculating a lower differential from the difference in the charge inputs at the two charging levels comprising the lower pair of charging levels and calculating an upper differential from the difference in the charge inputs at the two charging levels comprising the upper pair of charging levels, e) comparing the lower differential and the upper differential, f) adjusting the base charging level based on the differential comparison, and g) periodically repeating the steps a)-f), thereby repeatedly adjusting the base charging level to provide a more optimal battery charging profile.

45. The method of claim 44 further comprising the step of delaying for a delay time before performing step g.