Lithium polymer battery charger methods and apparatus

• US 5,773,959 A
• Filed: 01/11/1996
• Issued: 06/30/1998
• Est. Priority Date: 01/11/1996
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Merritt, Lauren V., Hollandsworth, Roger Paul, Rodriguez, Zaid B., Teofilo, Vincent L., Lovgren, Jack G.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): TOATLEY, GREGORY J
• Application Number:
  US08/582,527
• Time in Patent Office: 901 Days
• Field of Search: 320/15, 320/17, 320/18, 320/117, 320/116, 320/119, 320/122, 320/120, 320/104
• US Class Current: 320/120
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/0018 using separate charge circuits
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Lithium polymer battery charger methods for charging a plurality of equal charge point lithium polymer battery cells prevent overcharging of any cell, whether the cells are arranged in a series stack or are arranged in parallel. When the cells are connected in a series stack, a power supply is connected to the series stack to apply a charge current to the series stack. The state of charge of each cell in the stack is monitored. Information that the state of charge of any cell is approaching full charge is used to control the charge current and to prevent overcharging of any cell.

Claims

1. A method of charging a plurality of equal charge point lithium polymer battery cells, said method comprising,

connecting the cells in a series stack,

connecting a power supply to the series stack,

applying a charge current to the series stack from the power supply,

monitoring the state of charge of each cell in the stack,

detecting when the state of charge in any cell is approaching full charge, and

controlling the charge current to each cell in response to said detecting to prevent overcharging of any cell, and wherein the controlling of the charge current includes reducing the charge current to a trickle charge to the series stack when any one cell reaches full charge.

2. A method of charging a plurality of equal charge point lithium polymer battery cells to substantially fully charged conditions without overcharging any cell, said method comprising,

connecting the cells in a series stack,

connecting a power supply to the series stack,

applying a charge current to the series stack from the power supply,

monitoring the state of charge of each cell in the stack,

detecting when the state of charge in any cell is approaching full charge, and

controlling the charge current to each cell in response to said detecting to prevent overcharging of any cell, including using multiple power supplies for supplying multiple charge currents and connecting a single lithium polymer battery cell to each power supply.

3. The method defined in claim 2 wherein the multiple power supplies comprise multiple secondary windings of a transformer.

4. A method of charging a plurality of equal charge point lithium polymer battery cells, said method comprising,

connecting the cells in a series stack,

connecting a power supply to the series stack,

applying a charge current to the series stack from the power supply,

monitoring the state of charge of each cell in the stack,

detecting when the stage of charge in any cell is approaching full charge, and

controlling the charge current to each cell in response to said detecting to prevent overcharging of any cell, and including varying the individual charge currents to individual cells during the charging of the series stack said varying the individual charge currents including using multiple power supplies for supplying multiple charge currents and connecting a single lithium polymer battery cell to each power supply so that each cell is recharged by an individual cell charge current.

5. A method of charging a plurality of equal charge point lithium polymer battery cells, said method comprising,

connecting the cells in a series stack,

connecting a power supply to the series stack,

applying a charge current to the series stack from the power supply,

monitoring the state of charge of each cell in the stack,

detecting when the stage of charge in any cell is approaching full charge, and

controlling the charge current to each cell in response to said detecting to prevent overcharging of any cell, and including pre-emptively shunting a first particular amount of current around a first particular individual cell that requires less charge than other cells in the series stack and starting said shunting at a particular selected point in the charging of the series stack substantially prior to the time said first particular individual cell approaches full charge and shunting another amount of current around another particular individual cell at another particular selected point in the charging of the series stack to control the net charge to all of the cells so that all of the cells reach full charge at the same time.

6. A method of charging a plurality of equal charge point lithium polymer battery cells, said method comprising,

connecting the cells in a series stack,

connecting a power supply to the series stack,

applying a charge current to the series stack from the power supply,

monitoring the state of charge of each cell in the stack, and

controlling the charge current to each cell to prevent overcharging of any cell,

said controlling including shunting an amount of current around a first particular cell at a particular selected point in the charging of the series stack and shunting another amount of current around another individual cell at another particular selected point in the charging of the series stack.

7. The method defined in claim 6 wherein said shunting includes shunting only a part of the charging current around said particular cells at said particular selected points in the charging of the series stack.

8. A method of charging a plurality of equal charge point lithium polymer battery cells, said method comprising,

connecting the cells in a series stack,

connecting a power supply to the series stack,

applying a charge current to the series stack from the power supply,

monitoring the state of charge of each cell in the stack, and

controlling the charge current to each cell to prevent overcharging of any cell,

said controlling including shunting an amount of current around a first particular cell at a particular selected point in the charging of the series stack and shunting amount of another current around another individual cell at another particular selected point in the charging of the series stack, and

wherein said shunting includes shunting only a part of the charging current around said particular cells at said particular selected points in the charging of the series stack, and wherein the shunting includes shunting substantially all of the charging current around said particular cells but permits a trickle charging current to continue to flow to said particular cells.