Battery charger and charging method

• US 6,954,051 B2
• Filed: 07/09/2004
• Issued: 10/11/2005
• Est. Priority Date: 02/28/2002
• Status: Expired due to Fees

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Brotto, Daniele C., White, Paul S., Trinh, Danh T.
• Primary Examiner(s): Tibbits, Pia
• Application Number:
  US10/888,642
• Publication Number:
  US 20040257049A1
• Time in Patent Office: 459 Days
• Field of Search: 320/145, 320/107, 320/128, 320/130, 320/139, 320/141, 320/151
• US Class Current: 320/145
• CPC Class Codes: H02J 7/0071 with a programmable schedule
• CPC Class Codes: H02J 7/00711 with introduction of pulses during the charging process
• CPC Class Codes: H02J 7/007184 in response to battery voltage gradient
• CPC Class Codes: H02J 7/04 Regulation of charging current or voltage

Abstract

The charging method includes the steps of charging a battery pack, sensing voltage of the battery pack, calculating voltage change rate, detecting a first inflection point based on the voltage change rate so long as a voltage step is not detected, detecting a second inflection point based on the voltage change rate so long as a voltage step is not detected, and reducing current sent to the battery pack when both first and second inflection points have been detected.

Claims

1. A method for charging batteries comprising the steps of:

providing a current source for providing current to a battery pack during a fast charge cycle, the current source having an amperage rating;

after the fast charge cycle, commencing an equalization cycle comprising repeatedly pulsing the current source to provide a pulsed current to the battery pack, wherein a pulse of such pulsed current has an on-time having a first predetermined period of time and an off-time having a second predetermined period of time, the battery pack not being discharged between pulses of such pulsed current;

wherein the first predetermined period of time is between about 5 milliseconds and 250 milliseconds, and the second predetermined period of time is determined by the following equation;

t_OFF=t_ON (I/I_O)−

t_ON, where

I_O is the effective output current of the pulsed current

t_ON is the first predetermined period of time,

t_OFF is the second predetermined period of time, and

I is the amperage rating of the current source.

2. The method of claim 1, wherein value of the effective output current of the pulsed current is between around 1 milliamp and around 100 milliamp.

3. The method of claim 2, wherein the amperage rating of the current source is about 2.5 amps.

4. The method of claim 1, wherein the first predetermined period of time is about 10 milliseconds.

5. The method of claim 4, wherein the second predetermined period of time is about 240 milliseconds.

6. The method of claim 4, wherein the amperage rating of the current source is about 2.5 amps.

7. The method of claim 1, wherein the second predetermined period of time is about 240 milliseconds.

8. The method of claim 7, wherein the amperage rating of the current source is about 2.5 amps.

9. The method of claim 7, wherein the first predetermined period of time is about 10 milliseconds.