Battery Charger with Integrated Cell Balancing

• US 20080309286A1
• Filed: 06/11/2008
• Published: 12/18/2008
• Est. Priority Date: 06/15/2007
• Status: Active Grant

• Current Assignee: Duracell U.S. Operations, Inc. (Berkshire Hathaway Incorporated)
• Original Assignee: Gillette Company (The Procter & Gamble Company)
• Inventors: Hoff, Michael
• Granted Patent: US 8,098,048 B2
• Time in Patent Office: Days
• US Class Current: 320/107
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/0019 using switched or multiplexed charge circuits

Abstract

A battery charger containing circuitry including integrated cell balancing and automatic cell configuration determination is presented. The charger automatically adapts output current to different battery configurations. The charger also ensures that all the cells within a battery configuration are at roughly the same voltage.

Claims

1. A battery charger, comprising:

circuitry including integrated cell balancing and automatic cell configuration determination that automatically adapts output current to different battery configurations.

2. The battery charger of claim 1 wherein the integrated cell balancing includes a regulated switching power supply to charge a pack of cells.

3. The battery charger of claim 2, wherein the pack of cells may be one from the group comprising a one series (1S), a two series (2S), a three series (3S), or a four series (4S).

4. The battery charger of claim 2, further comprising:

a resistive load network including individual resistors, each individual resistor connected in parallel across each cell in the pack of cells to all but the cell with the smallest voltage in the pack wherein cell balancing continuously attempts to bring all the cells in the pack of cells to the same voltage by drawing current from the cells with the most charge, until all cells have the same amount of stored charge.

5. The battery charger of claim 1 wherein the integrated cell balancing includes a controller that monitors electrical and temperature conditions inside the charger, maintains proper individual cell voltages, detects fault conditions and displays charger status and charge progress.

6. The battery charger of claim 1 further comprising circuitry to sense the battery voltage on output terminals of the charger and the individual cell voltages on inter-cell connection ports.

7. The battery charger of claim 1 wherein the charger determines the battery configuration connected to the charger and adjusts the output voltage and balancing according to the determined configuration.

8. The battery charger of claim 1 wherein the charger monitors individual cell voltages to maintain all cell voltages equal to each other within a specified tolerance.

9. The battery charger of claim 1 further comprising:

a first connector for the main charge path; and

an auxiliary connector attached to inter-cell points in the pack to the charger for balancing and individual cell voltage monitoring.

10. The battery charger of claim 1 wherein the charger senses how many inter-cell connections are attached to the charger and determines how many cells are in series in the pack.

11. The battery charger of claim 1 wherein the charger uses inter-cell connections to drain small amounts of current from the higher voltage cells to accomplish cell voltage balancing.

12. The battery charger of claim 1 wherein the circuitry samples the input and output cell voltages and the inductor current at regular time intervals.

13. The battery charger of claim 1 wherein the charger determines the number of cells connected to the charger by measuring the impedance across each possible cell connection, with a high impedance between two terminals indicating no cell connected to the terminals and a low impedance along with at least a volt of dc voltage indicating a cell connected to those terminals.

14. The battery charger of claim 1 wherein if the charger senses that one of the cells in the string is at or above its target value, the charger adjusts the total output voltage lower to keep that cell at its target value to drain current from that cell that is at or above the target voltage value.

15. The battery charger of claim 1 wherein the cell sensing and voltage adjustment is done about every millisecond.

16. The battery charger of claim 1 wherein a resistive load is applied to the cells by turning on a transistor that connects a resistor across the terminals of the higher-voltage cell, with the value of the resistor determining a balancing current.

17. The battery charger of claim 1 wherein if the cell voltages are within 10 millivolts of each other no balancing action is performed.

18. The battery charger of claim 1 wherein the charger includes a thermistor or other temperature sensing component disposed inside the charger near the charger'"'"'s hottest power components.

19. A battery charger, comprising:

circuitry to sense battery voltage on output terminals of the charger and

circuitry to sense individual cell voltages on inter-cell connection ports of the charger; and

circuitry to determine whether one of the cells in the string is at or above its target value, and to adjust the total output voltage lower to keep that cell at its target value to drain current from that cell that is at or above the target voltage value.

20. A battery charger, comprising:

circuitry to sense battery voltage on output terminals of the charger and circuitry to sense individual cell voltages on inter-cell connection ports of the charger; and

a resistor

a transistor coupled to the resistor; and

circuitry to apply the resistive load to a selected one or ones of the cells by turning on a transistor that connects a resistor across the terminals of the higher-voltage cell, with the value of the resistor determining the balancing current.

21. A battery charger, comprising:

circuitry to charge a nanophosphate cell in about 15 minutes, the circuitry including integrated cell balancing and with the circuitry automatically adapting to different connected battery configurations.

22. The battery charger of claim 21 wherein the integrated cell balancing includes a regulated switching power supply to charge a pack of cells.

23. The battery charger of claim 22, wherein the pack of cells may be one from the group comprising a one series (1S), a two series (2S), a three series (3S), or a four series (4S).

24. The battery charger of claim 21, further comprising:

a resistive load network including individual resistors, each individual resistor having a distinct resistance that is variably adjusted and inserted in series between each cell in the pack of cells to all but the cell with the smallest voltage in the pack wherein cell balancing continuously attempts to bring all the cells in the pack of cells to the same voltage by varying each resistance corresponding to an individual resistor in the resistive load network.

25. The battery charger of claim 24 wherein the integrated cell balancing includes a controller that monitors electrical and temperature conditions inside the charger, maintains proper individual cell voltages, detects fault conditions and displays charger status and charge progress.