Battery charging system employing multi-mode low power fast charge process

• US 6,215,282 B1
• Filed: 06/19/2000
• Issued: 04/10/2001
• Est. Priority Date: 06/19/2000
• Status: Expired due to Term

• Current Assignee: Omnitracs LLC (Solera Holdings Incorporated)
• Original Assignee: Qualcomm, Inc.
• Inventors: Hardgrove, Charles E., Richards, Anthony M.
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/597,889
• Time in Patent Office: 295 Days
• Field of Search: 320/124, 320/125, 320/132, 320/134, 320/136, 320/155, 320/157, 320/160, 320/162, 320/164
• US Class Current: 320/160
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

An especially low power, fast completion battery charge process varies the voltage, current, and time of charging a battery according to the battery'"'"'s state of charge. Initially, a battery charger apparatus applies a fast charge current to the battery. When the battery voltage increases to a target voltage, the battery charger applies a fast charge voltage to the battery. This continues until the current flowing through the battery decreases to a prescribed minimum current. The battery charger then calculates the elapsed time between the battery'"'"'s initially receiving the fast charge current and later achieving the minimum current. Using the elapsed time, the charger computes a proposed overcharge time comprising a multiplicative product of the elapsed time and a temperature-dependent adjustment factor. Next, the battery charger applies an overcharge voltage to the battery for the proposed overcharge time, unless the proposed overcharge time exceeds a prescribed maximum time. In that event, the battery charger applies the overcharge voltage to the battery for the prescribed maximum time.

Claims

1. A battery charging method, comprising operations of:

applying a constant current to the battery at a first time;

determining when battery voltage has risen to a target voltage, and substantially thereupon applying a fast charge voltage to the battery;

determining a second time when battery charge current has decreased to a target charge current;

substantially at the second time, determining an elapsed time between the first and second times;

computing a proposed overcharge time comprising a multiplicative product of the elapsed time and an adjustment factor;

computing an actual overcharge time comprising the proposed overcharge time, limited to a prescribed maximum time; and

applying an overcharge voltage to the battery for a length of time substantially equal to the actual overcharge time.

2. The method of claim 1, where the operation of computing the proposed overcharge time comprises:

multiplying the elapsed time by an adjustment factor that includes a temperature coefficient of increasing values for colder battery temperatures and decreasing values for warmer battery temperatures.

3. The method of claim 1, where the target voltage is substantially equal to the fast charge voltage.

4. The method of claim 1, where the overcharge voltage exceeds the fast charge voltage.

5. The method of claim 1, where:

the battery is removably attached to an electrical load;

the operations further include detaching the battery from the load during the operation of determining the second time.

6. The method of claim 1, the operations further comprising:

limiting the second time to a predetermined maximum safety time.

7. The method of claim 1, the operations further comprising:

after applying the overcharge voltage to the battery for the length of time substantially equal to the actual overcharge time, applying a trickle charge voltage to the battery.

8. The method of claim 7 where the target charge current is at least ten times greater than battery current during application of the trickle charge voltage.

9. The method of claim 7, where the fast charge voltage exceeds the trickle voltage.

10. A battery charging method, comprising operations of:

applying a first prescribed current to a battery until battery voltage increases to a first prescribed voltage;

applying a second prescribed voltage to the battery until current passing through he battery decreases to a second prescribed current;

applying a third prescribed voltage to the battery for a calculated length of time substantially equal to;

an adjustment factor multiplied by added times of the application of the first described current and second prescribed voltage to the battery;

wherein, in any event, said calculated length of time is limited to a predetermined maximum time.

11. The method of claim 10, the first and second voltage being substantially equal.

12. The method of claim 10, further comprising :

applying a fourth prescribed voltage to the battery upon the expiration of the calculated length of time.

13. A signal-bearing medium tangibly embodying a program of machine-readable instructions executable by a digital processing apparatus to perform a method for charging a battery, said method comprising operations of:

applying a constant current to the battery at a first time;

determining when battery voltage has risen to a target voltage, and substantially thereupon applying a fast charge voltage to the battery;

determining a second time when battery charge current has decreased to a target charge current;

substantially at the second time, determining an elapsed time between the first and second times;

computing a proposed overcharge time comprising a multiplicative product of the elapsed time and an adjustment factor;

computing an actual overcharge time comprising the proposed overcharge time limited to a prescribed maximum time; and

applying an overcharge voltage to the battery for a length of time substantially equal to the actual overcharge time.

14. A signal-bearing medium tangibly embodying a program of machine-readable instructions executable by a digital processing apparatus to perform a method for charging a battery, said method comprising operations of:

applying a first prescribed current to a battery until battery voltage increases to a first prescribed voltage;

applying a second prescribed voltage to the battery until current passing through the battery decreases to a second prescribed current;

applying a third prescribed voltage to the battery for a calculated length of time substantially equal to;

an adjustment factor multiplied by added times of the application of the first prescribed current and second prescribed voltage to the battery;

wherein, in any event, said calculated length of time is limited to a predetermined maximum time.

15. A logic circuit of multiple interconnected electrically conductive elements configured to perform operations to charge a battery, the operations comprising:

battery charging method, comprising operations of;

applying a constant current to the battery at a first time;

determining when battery voltage has risen to a target voltage, and substantially thereupon applying a fast charge voltage to the battery;

determining a second time when battery charge current has decreased to a target charge current;

substantially at the second time, determining an elapsed time between the first and second times;

computing a proposed overcharge time comprising a multiplicative product of the elapsed time and an adjustment factor;

computing an actual overcharge time comprising the proposed overcharge time, limited to a prescribed maximum time; and

applying an overcharge voltage to the battery for a length of time substantially equal to the actual overcharge time.

16. A logic circuit of multiple interconnected electrically conductive elements configured to perform operations to charge a battery, the operations comprising:

applying a first prescribed current to a battery until battery voltage increases to a first prescribed voltage;

applying a second prescribed voltage to the battery until current passing through the battery decreases to a second prescribed current;

applying a third prescribed voltage to the battery for a calculated length of time substantially equal to;

an adjustment factor multiplied by added times of the application of the first prescribed current and second prescribed voltage to the battery;

wherein, in any event, said calculated length of time is limited to a predetermined maximum time.

17. A battery charger system, comprising:

a charger circuit;

coupled to the charger circuit,

a power source node;

a second node;

a third node;

the charger circuit being programmed to charge a battery attached between the second and third nodes by;

applying a constant current to the battery at a first time;

determining when battery voltage has risen to a target voltage, and substantially thereupon applying a fast charge voltage to the battery;

determining a second time when battery charge current has decreased to a target charge current;

substantially at the second time, determining an elapsed time between the first and second times;

computing a proposed overcharge time comprising a multiplicative product of the elapsed time and an adjustment factor;

computing an actual overcharge time comprising the proposed overcharge time, limited to a prescribed maximum time; and

applying the overcharge voltage to the battery for a length of time substantially equal to the actual overcharge time.

18. The apparatus of claim 17, further comprising:

electrical coupling to place an electrical load in parallel with the battery;

the coupling including a switch to selectively decouple the battery from the load.

19. The apparatus of claim 17, further comprising:

electrical coupling to place an electrical load in parallel with the battery;

the coupling including a switch to selectively decouple the battery from the load, the switch being remotely operated by the charger circuit;

the charger circuit being further programmed to detach the battery from the load during the operation of determining the second time.

20. A battery charger system, comprising:

a charger circuit;

coupled to the charger circuit,

a power source node;

a second node for connection to a positive battery terminal;

a third node for connection to a negative battery terminal;

the charger circuit being programmed to charge a battery attached between the second and third nodes by;

applying a first prescribed current to a battery until battery voltage increases to a first prescribed voltage;

applying a second prescribed voltage to the battery until current passing through the battery decreases to a second prescribed current;

applying a third prescribed voltage to the battery for a calculated length of time substantially equal to;

an adjustment factor multiplied by added times of the application of the first prescribed current and second prescribed voltage to the battery;

wherein, in any event, said calculated length of time is limited to a predetermined maximum time.

21. A battery charger system, comprising:

a power source node;

a second node for connection to a positive battery terminal;

a third node for connection to a negative battery terminal;

charger means coupled to the power, second, and third nodes, for charging a battery attached between the second and third nodes by;

applying a constant current to the battery at a first time;

determining when battery voltage has risen to a target voltage, and substantially thereupon applying a fast charge voltage to the battery;

determining a second time when battery charge current has decreased to a target charge current;

substantially at the second time, determining an elapsed time between the first and third times;

computing a proposed overcharge time comprising a multiplicative product of the elapsed time and an adjustment factor;

computing an actual overcharge time comprising the proposed overcharge time, limited to a prescribed maximum time; and

applying the overcharge voltage to the battery for a length of time substantially equal to the actual overcharge time.

22. A battery charger system, comprising:

a power source node;

a second node for connection to a positive battery terminal;

a third node for connection to a negative battery terminal;

charging means coupled to the power, second, and third nodes for charging a battery attached between the second and third nodes by;

applying a first prescribed current to a battery until battery voltage increases to a first prescribed voltage;

applying a second prescribed voltage to the battery until current passing through the battery decreases to a second prescribed current;

applying a third prescribed voltage to the battery for a calculated length of time substantially equal to;

an adjustment factor multiplied by added times of the application of the first prescribed current and second prescribed voltage to the battery;

wherein, in any event, said calculated length of time is limited to a predetermined maximum time.