Method and apparatus for battery charging

• US 6,320,354 B1
• Filed: 07/21/2000
• Issued: 11/20/2001
• Est. Priority Date: 07/21/2000
• Status: Expired due to Term

• Current Assignee: Amperex Technology Limited (TDK Corporation)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Oglesbee, John W., Sengupta, Upal
• Primary Examiner(s): TOATLEY, GREGORY J
• Application Number:
  US09/621,266
• Time in Patent Office: 487 Days
• Field of Search: 320/139, 320/145, 320/157, 320/132, 340/636, 324/433
• US Class Current: 320/132
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/46 Accumulators structurally combined with charging apparatus circuits for charging H02J7/00
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery charging circuit comprises a recharge input and a recharge output with a switching element electrically coupled in series between the recharge input and output. A recharge controller controls a conducting state of the switching element. When in a conducting state, recharge current can flow from the recharge input to the recharge output, thereby allowing a rechargeable battery coupled to the recharge output to be recharged. During periodically occurring intervals, the recharge controller switches the switching element to a non-conducting state such that the recharge current no longer flows to the recharge output. During the intervals, a battery voltage input is sampled to determine a charge state of the battery. The switching element is subsequently returned to a conducting state when further recharging is necessary, or left in a non-conducting state when sufficient recharging has occurred.

Claims

1. A method for determining charge status during charging of a rechargeable battery, the method comprising steps of:

electrically coupling the battery to a recharge voltage source;

determining when a measured voltage of the battery has reached a threshold voltage;

during a periodic interval, electrically de-coupling the battery from the recharge voltage source;

during the periodic interval, allowing the battery voltage to stabilize during a settling period;

sampling an output voltage of the battery; and

electrically re-coupling the battery to the recharge voltage source when the output voltage sampled during the periodic interval is below the threshold voltage.

2. The method of claim 1, further comprising a step of:

displaying a charge status based on the output voltage of the battery.

3. The method of claim 1, wherein the steps of electrically de-coupling, allowing, sampling, and electrically re-coupling are repeated until the output voltage is maintained at the threshold voltage, indicating a full charge of the battery.

4. The method of claim 2, wherein the step of sampling includes determining if the battery voltage stays at the desired threshold voltage, indicating a full charge of the battery.

5. The method of claim 1, wherein a periodicity of the periodic interval is within a range of two to ten minutes.

6. The method of claim 5, wherein the periodicity of the periodic interval is approximately five minutes.

7. The method of claim 1, wherein duration of the settling period is within a range from one second to one minute.

8. A battery charging circuit for determining charge status during charging of a rechargeable battery, the circuit comprising:

a recharge input;

a recharge output;

a switching element electrically coupled in series between the recharge input and the recharge output;

a battery voltage input; and

a recharge controller, coupled to the battery voltage input and the switching element, that maintains the switching element in a conducting state wherein recharge current flows from the recharge input to the recharge output until the battery voltage input reaches a threshold voltage, and that then during a periodic interval switches the switching element between a non-conducting state wherein the recharge current does not flow to the recharge output and that samples the battery voltage input to determine a charge state of a battery coupled to the recharge output and a conducting state, wherein during the periodic interval the battery voltage is allowed to stabilize during a settling period before measurement, and the battery voltage is sampled during each periodic interval until the battery maintains the threshold voltage, indicating a full charge of the battery.

9. The battery charging circuit of claim 8, wherein the switching element is a solid-state switching element.

10. The battery charging circuit of claim 9, wherein the switching element is a MOSFET transistor.

11. The battery charging circuit of claim 8, further comprising a current flow inhibitor electrically coupled in series between the recharge input and the switching element that prevents current from flowing towards the recharge input.

12. The battery charging circuit of claim 8, wherein the recharge controller comprises:

a processor;

an analog-to-digital converter electrically coupled between the battery voltage input and the processor; and

a memory having stored thereon instructions, executable by the processor, for maintaining the switching element in the conducting state wherein the recharge current flows from the recharge input to the recharge output, switching the switching element to the non-conducting state during the periodic interval wherein the recharge current does not flow to the recharge output, and sampling the battery voltage input during the periodic interval to determine the charge state of the battery coupled to the recharge output.

13. The battery charging circuit of claim 8, wherein a periodicity of the periodic interval is within a range of two to ten minutes.

14. The battery charging circuit of claim 13, wherein the periodicity of the periodic interval is approximately five minutes.

15. The battery charging circuit of claim 8, wherein duration of the settling period is within a range from one second to one minute.

16. A wireless communication unit comprising:

a battery charging circuit for determining charge status during charging of a rechargeable battery, the circuit comprising;

a recharge input;

a recharge output;

a switching element electrically coupled in series between the recharge input and the recharge output;

a battery voltage input; and

a recharge controller, coupled to the battery voltage input and the switching element, that maintains the switching element in a conducting state wherein recharge current flows from the recharge input to the recharge output until the battery voltage input reaches a threshold voltage, and that then during a periodic interval switches the switching element between a non-conducting state wherein the recharge current does not flow to the recharge output and that samples the battery voltage input to determine a charge state of a battery coupled to the recharge output and a conducting state, wherein during the periodic interval the battery voltage is allowed to stabilize during a settling period before measurement, and the battery voltage is sampled during each periodic interval until the battery maintains the threshold voltage, indicating a full charge of the battery.

17. The wireless communication unit of claim 16, further comprising an indicator coupled to the recharge controller for indicating a charge status based on samples of the battery voltage input.