METHOD AND SYSTEM FOR CELL EQUALIZATION WITH ISOLATED CHARGING SOURCES

• US 20060097696A1
• Filed: 10/26/2005
• Published: 05/11/2006
• Est. Priority Date: 11/10/2004
• Status: Active Grant

• Current Assignee: Eaglepicher Technologies LLC (Eaglepicher Corporation)
• Original Assignee: Eaglepicher Technologies LLC (Eaglepicher Corporation)
• Inventors: Miller, Greg, Shimp, Phillip, Pennock, Tim, Coatney, Eric, Studyvin, William
• Granted Patent: US 7,928,691 B2
• Time in Patent Office: Days
• US Class Current: 320/116
• CPC Class Codes: H02J 7/0018 using separate charge circuits

Abstract

A system and method for charging a rechargeable, or secondary, battery including a series string of battery cells, a topology of charging sources that selectively provides charging current to battery cells that need to be charged, but avoids overcharging battery cells that are already charged above a predetermined voltage threshold. Based on individual cell voltage measurements, the charging current is controlled in a manner to direct charging current to the battery cell(s) needing charge until these cells are fully charged, and bypasses battery cells that are fully charged or become fully charged.

Claims

1. A charging system for charging a rechargeable battery, comprising:

N battery cells coupled in series forming a series string, wherein said series string comprises;

a first battery cell coupled to a load end, and

a N^th battery cell coupled to a ground end;

a plurality of charging sources coupled in parallel to said series string;

a plurality of positive paths coupled to said series string and said charging sources; and

a plurality of negative paths coupled to said series string and said charging sources,

wherein a charging source is coupled in parallel to each respective battery cell via a respective positive path and a respective negative path.

2. The charging system of claim 1, wherein each charging source is coupled to a power source.

3. The charging system of claim 2, wherein each charging source is configured to provide charging current to each respective battery cell via said positive path, and return charging current to said charging source via said negative path.

4. The charging system of claim 1, wherein each charging source is configured to operate in one of a first state and a second state, wherein when operating in said first state each charging source provides charging current to said respective battery cell, and when operating in said second state does not provide charging current to said respective battery cell.

5. The charging system of claim 4, further comprising:

a controller, where said controller is coupled to each of said charging sources.

6. The charging system of claim 5, wherein said controller is configured to selectively operate each charging source in one of said first state and said second state.

7. The charging system of claim 1, further comprising:

a plurality of cell monitors coupled to said series string, wherein each cell monitor is coupled to a respective battery cell, and is configured to measure an amount of voltage contained in said respective battery cell; and

a controller coupled to each cell monitor and coupled to each charging source, wherein said charging sources are controlled by said controller to provide charging current to their respective battery cells when said battery cell contains an amount of voltage below a threshold amount, and to not provide charging current to said battery cell when said battery cell contains an amount of voltage above said threshold amount.

8. A method for cell equalization of a secondary battery being charged, the method comprising the steps of:

coupling N battery cells in series to form a series string, wherein said coupling N battery cells step comprises the steps of;

coupling a first cell to a load end, and

coupling a N^th battery cell to a ground end;

coupling a plurality of charging sources to said series string, wherein each charging source is coupled in parallel across one of said N battery cells; and

configuring said charging sources to selectively provide charging current to one or more of said N battery cells.

9. The method of claim 8, wherein said configuring said charging sources step comprises the steps of:

configuring a particular charging source to operate in a first state to provide charging current to said respective battery cell; and

configuring each charging source to operate in a second state to not provide charging current to said one or more of said N battery cells.

10. The method of claim 8, further comprising the step of:

coupling each charging source to a power source.

11. The method of claim 8, further comprising the steps of:

configuring said charging sources to provide charging current to each battery cell containing an amount of voltage below a threshold amount, and to not provide charging current to each battery cell containing an amount of voltage above said threshold amount.

12. The method of claim 11, further comprising the steps of:

coupling a plurality of cell monitors to said series string to monitor a respective voltage level in said N battery cells, determine which of said N battery cells contains an amount of voltage above said threshold amount, and determine which of said N battery cells contains an amount of voltage below said threshold amount.

13. A method for equalizing the cell voltage of a secondary battery comprising the steps of:

coupling two or more battery cells in series to form a series string;

coupling in parallel across each battery cell an associated charging source;

charging any battery cell including an amount of voltage below a threshold level with a respective associated charging source; and

not charging any battery cell including an amount of voltage above said threshold level.

14. The method of claim 13, wherein said step of charging a particular cell comprises the steps of:

switching ON a respective charging source to charge an associated battery cell including an amount of voltage below said threshold level; and

switching OFF said respective charging source to avoid overcharging said associated battery cell when said associated battery cell includes an amount of voltage above said threshold level.

15. The method of claim 13, further comprising the steps of:

monitoring a respective voltage level of each of said battery cells; and

independently operating each of said charging sources in an ON state or an OFF state based on said respective voltage level of each of said battery cells.

16. The method of claim 13, wherein said step of charging any cell comprises the step of:

providing charging current to a particular battery cell via said respective associated charging source.

17. The method of claim 16, wherein said step of charging a particular cell further comprises the step of:

returning said charging current to said respective associated charging source via a negative path.

18. The method of claim 13, further comprising the steps of:

monitoring a respective voltage level in each of said N battery cells;

determining which of said N battery cells contains an amount of voltage above said threshold level; and

determining which of said N battery cells contains an amount of voltage below said threshold level.