Battery charging method and system with three-stage temperature-compensated charge profile

• US 8,841,884 B2
• Filed: 11/02/2010
• Issued: 09/23/2014
• Est. Priority Date: 11/02/2010
• Status: Active Grant

• Current Assignee: Enerpro, Inc.
• Original Assignee: Enerpro, Inc.
• Inventors: Bourbeau, Frank J., Matherly, James T.
• Primary Examiner(s): Tso, Edward
• Assistant Examiner(s): TORRES RUIZ, JOHALI ALEJANDRA
• Application Number:
  US12/938,154
• Publication Number:
  US 20110140672A1
• Time in Patent Office: 1,421 Days
• Field of Search: 320/139
• US Class Current: 320/134
• CPC Class Codes: H02J 7/007184 in response to battery voltage gradient
• CPC Class Codes: H02J 7/007194 of the battery

Abstract

A battery charging method and system with a temperature-compensated charge profile requires that, during a ‘bulk stage’, a regulated constant charge current is provided to the battery until the voltage across it increases to a predetermined ‘absorption stage voltage limit’, at which time charging transitions to an ‘absorption stage’. During the absorption stage, a charge current is provided which maintains the voltage across the battery at the absorption stage voltage limit, until: 1) the charge current falls to a predetermined current threshold, 2) the charge delivered to the battery during the absorption stage reaches a predetermined charge threshold, or 3) the difference in charge between two successive intervals of equal duration becomes zero, at which time charging transitions to a ‘float stage’. During the ‘float stage’, a regulated constant charge current is provided, such that the voltage across the battery varies with the temperature of the battery.

Claims

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

providing, during a ‘

bulk stage’

, a regulated charge current to said battery until the voltage across said battery increases to a predetermined ‘

absorption stage voltage limit’

at which time charging transitions to an ‘

absorption stage’

;

providing, during said ‘

absorption stage’

, a charge current to said battery which maintains the voltage across said battery at said predetermined ‘

absorption stage voltage limit’

;

determining when a first condition occurs, said first condition being when said charge current falls to a predetermined ‘

absorption stage current threshold’

value;

determining when a second condition occurs, said second condition being when the charge in ampere-hours delivered to said battery during said absorption stage rises to a predetermined ‘

absorption stage charge threshold’

value;

determining when a third condition occurs, said third condition being when the difference in charge between two successive fixed time intervals of equal duration becomes approximately zero;

transitioning charging to a ‘

float stage’

when any of said three conditions are met; and

providing, during said ‘

float stage’

, a constant charge current to said battery such that the voltage across said battery varies with the temperature of said battery.

2. The method of claim 1, wherein said regulated charge current provided during said bulk stage is a constant current.

3. The method of claim 2, wherein said constant current provided during said bulk stage is a predetermined percentage of said battery'"'"'s amp-hour capacity.

4. The method of claim 2, wherein said constant current provided during said bulk stage is approximately 20% of said battery'"'"'s amp-hour capacity.

5. The method of claim 1, wherein said predetermined absorption stage current threshold value is a predetermined percentage of said battery'"'"'s amp-hour capacity.

6. The method of claim 5, wherein said predetermined absorption stage current threshold value is approximately 6% of said battery'"'"'s amp-hour capacity.

7. The method of claim 1, wherein said predetermined absorption stage charge threshold value is a predetermined percentage of said battery'"'"'s amp-hour capacity.

8. The method of claim 7, wherein said predetermined absorption stage charge threshold value is approximately 10% of said battery'"'"'s amp-hour capacity.

9. The method of claim 1, wherein said constant current provided during said float stage is a predetermined percentage of said battery'"'"'s amp-hour capacity.

10. The method of claim 9, wherein said constant current provided during said float stage is approximately 1% of said battery'"'"'s amp-hour capacity.

11. The method of claim 1, wherein said battery is a flooded lead-acid battery.

12. The method of claim 1, wherein said battery is a valve-regulated lead-acid battery.

13. The method of claim 1, wherein said battery is intended for use in a locomotive.

14. The method of claim 1, wherein said battery is intended for use in a materials-handling vehicle or a golf cart.

15. A battery charging system, comprising:

circuitry arranged to provide a charge current to and a voltage across a battery to be charged; and

a controller arranged to operate said circuitry such that;

during a ‘

bulk stage’

, said circuitry provides a regulated charge current to said battery until the voltage across said battery increases to a predetermined ‘

absorption stage voltage limit’

at which time charging transitions to an ‘

absorption stage’

;

during said ‘

absorption stage’

, said circuitry provides a charge current to said battery which maintains the voltage across said battery at said predetermined ‘

absorption stage voltage limit’

,

said controller arranged to detect at least three conditions, a first condition being when said charge current falls to a predetermined ‘

absorption stage current threshold’

value, a second condition being when the amp-hour product delivered to said battery during said absorption stage reaches a predetermined ‘

absorption stage charge threshold’

value, a third condition being when the difference in charge between two successive fixed time intervals of equal duration becomes approximately zero, said controller further arranged to transition charging to a ‘

float stage’

when any of said first, second or third conditions are detected; and

during said ‘

float stage’

, said circuitry provides a constant charge current to said battery such that the voltage across said battery varies with the temperature of said battery.

16. The battery charging system of claim 15, wherein said circuitry comprises:

a generator; and

a rectifier arranged to receive and rectify an AC voltage from said generator and to provide said rectified voltage to said battery.

17. The battery charging system of claim 16, wherein said generator comprises a companion alternator and said rectifier is a thyristor rectifier.

18. The battery charging system of claim 16, wherein said generator and rectifier comprise a field current-controlled auxiliary generator and a diode rectifier, or a companion alternator and a thyristor rectifier.

19. The battery charging system of claim 15, wherein said controller comprises a microprocessor.

20. The battery charging system of claim 15, wherein said controller comprises an application specific integrated circuit (ASIC).

21. The battery charging system of claim 15, further comprising a current transducer connected in series with said battery to sense the current in said battery and to provide an output voltage that varies with said sensed current.

22. The battery charging system of claim 21, further comprising a comparator connected to receive said current transducer output and a reference voltage at respective inputs and to toggle an output when said charge current has fallen to said predetermined absorption stage current threshold value, said system arranged to transition from said absorption stage to said float stage when the output of said comparator toggles.

23. The battery charging system of claim 21, further comprising:

a voltage-controlled oscillator (VCO) connected to receive said current transducer output at an input and to provide an output having a frequency that varies with said current transducer output; and

a binary counter having a clock input that is connected to the output of said VCO;

said system arranged to transition from said absorption stage to said float stage when the count indicated by said counter indicates that the amp-hour product delivered to said battery during said absorption stage has reached said predetermined absorption stage charge threshold value.

24. The battery charging system of claim 21, further comprising:

a voltage-controlled oscillator (VCO) connected to receive said current transducer output at an input and to provide an output having a frequency that varies with said current transducer output;

an up/down counter having a clock input which is connected to the output of said VCO and an up/dn input; and

a fixed frequency oscillator (FFO) having an output which toggles periodically between logic 0 and logic 1 states, remaining in each state for fixed time intervals of equal duration, said FFO output applied to said up/dn input, said up/down counter arranged to count up or down in response to said VCO output based on the state of said FFO output;

said system arranged to transition from said absorption stage to said float stage when said up/down counter indicates that the difference in charge between two successive ones of said fixed time intervals is approximately zero.