Method and apparatus for rapid charging batteries under sub-optimal interconnect conditions

• US 6,172,481 B1
• Filed: 09/02/1999
• Issued: 01/09/2001
• Est. Priority Date: 09/02/1999
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Curtiss, Troy
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): LUK, LAWRENCE W
• Application Number:
  US09/389,291
• Time in Patent Office: 495 Days
• Field of Search: 320/127, 320/128, 320/132, 320/151, 320/152
• US Class Current: 320/127
• CPC Class Codes: H02J 7/007 Regulation of charging or discharging current or voltage

Abstract

A method and apparatus for rapid charging a battery that compensates for sub-optimal interconnection between the charger and the battery. In the present invention the effect of an imperfect interconnection between a charger and a battery is empirically characterized. The elements of the imperfect interconnection include any resistive losses between the battery charger output and the battery cells. The battery charger incorporates a control loop that measures the current flowing into the battery and the voltage at the interconnect terminals. The control loop then calculates the voltage at the actual batteries based on the measured values and the predetermined interconnect characterization. The control loop uses the calculation to adjust the output of the charger to achieve the optimal voltage at the batteries. The result of optimizing the charging voltage is a significant charge time reduction.

Claims

1. An apparatus for optimizing an output of a power supply to compensate for battery charging losses comprising:

a current sensor to determine a charging current supplied by the power supply;

means for determining a compensation value based on the charging current and a predetermined corresponding charging loss;

means for providing the compensation value to a control port on the power supply to adjust the output of the power supply to compensate for the charging losses.

2. An apparatus for optimizing an output of a power supply to compensate for battery charging losses comprising:

a series current sense resistor between the output of the power supply and an input of a charging battery;

means for determining a compensation value based on the voltage across the series current sense resistor and a predetermined corresponding charging loss;

means for providing the compensation value to a control port on the power supply to adjust the output of the power supply to compensate for the charging losses.

3. The apparatus of claim 2 wherein the means for determining a compensation value comprises:

a difference amplifier with a magnitude of gain less than or equal to a ratio of a resistive portion of the battery charging losses to the current sense resistor value.

4. The apparatus of claim 3 wherein the difference amplifier comprises:

an operational amplifier with a reference terminal resistively connected to a low voltage side of the current sense resistor, an inverting terminal resistively connected to a high voltage side of the current sense resistor, and an output terminal resistively connected to the inverting terminal.

5. The apparatus of claim 2 wherein the means for determining a compensation value comprises:

a multiplexer having a first input connected to a high voltage side of the current sense resistor and a second input connected to a low voltage side of the current sense resistor for sampling the voltage values;

an analog to digital (A/D) converter for converting the output of the multiplexer to digital values;

a memory device for storage of a predetermined compensation table having charging loss values corresponding to charging currents; and

a digital processor for calculating a current through the current sense resistor based upon the sampled voltage values and for determining the compensation value based on the calculated current and the contents of the predetermined compensation table.

6. The apparatus of claim 5 wherein the means for providing the compensation value comprises:

a digital to analog (D/A) converter which receives the compensation value from the digital processor and converts it to an analog value and outputs the analog value to the control port on the power supply.

7. An apparatus for charging a battery pack comprising:

a power supply having an output and a control port for controlling the output voltage; and

a monitor and control circuit for measuring the current being supplied by the power supply to an external load, determining a compensation value based on predetermined compensation measurements, and generating a compensation value to input to the control port on the power supply.

8. The apparatus of claim 7 wherein the predetermined compensation measurements are voltage drops with respect to charging current measured between the power supply output and battery cells within the battery pack.

9. The apparatus of claim 7 wherein the monitor and control circuit comprises:

a current sensor to determine a charging current supplied by the power supply;

means for determining a compensation value based on the charging current and a predetermined corresponding charging loss;

means for providing the compensation value to a control port on the power supply to adjust the output of the power supply to compensate for the charging losses.

10. The apparatus of claim 7 wherein the monitor and control circuit comprises:

a series current sense resistor between the output of the power supply and an input of a charging battery;

means for determining a compensation value based on a voltage across the series current sense resistor and a predetermined corresponding charging loss;

means for providing the compensation value to a control port on the power supply to adjust the output of the power supply to compensate for the charging losses.

11. The apparatus of claim 10 wherein the means for determining a compensation value comprises:

a difference amplifier with a magnitude of gain less than or equal to a ratio of a resistive portion of the battery charging losses to the current sense resistor value.

12. The apparatus of claim 11 wherein the difference amplifier comprises:

an operational amplifier with a reference terminal resistively connected to a low voltage side of the current sense resistor, an inverting terminal resistively connected to a high voltage side of the current sense resistor, and an output terminal resistively connected to the inverting terminal.

13. The apparatus of claim 10 wherein the power supply is a constant current constant voltage power supply.

14. The apparatus of claim 10 wherein the monitor and control circuit comprises:

a multiplexer having a first input connected to a high voltage side of the current sense resistor and a second input connected to a low voltage side of the current sense resistor;

an analog to digital (A/D) converter for converting the output of the multiplexer to digital values;

a memory device for storage of a predetermined compensation table;

a digital processor for calculating a current through the current sense resistor and for determining the compensation value based on the contents of the predetermined compensation table and the magnitude of said current; and

a digital to analog (D/A) converter which receives the compensation value from the digital processor and converts it to an analog value and outputs the analog value to the control port on the power supply.

15. A method of adjusting a battery charger output to compensate for charging losses comprising:

characterizing a battery pack charging loss with respect to a charging current;

monitoring the charging current from the battery charger to the battery pack;

determining a compensation value based upon the monitored charging current and the previously characterized battery pack charging loss; and

adjusting the battery charger output in accordance with the compensation value.