Battery cell balancing system and method

• US 8,896,315 B1
• Filed: 01/20/2012
• Issued: 11/25/2014
• Est. Priority Date: 02/12/2009
• Status: Active Grant

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Davies, Francis J.
• Primary Examiner(s): Phan, Huy Q
• Assistant Examiner(s): Rhodes-Vivour, Temilade S
• Application Number:
  US13/354,552
• Time in Patent Office: 1,040 Days
• Field of Search: 320117-127, 324/434
• US Class Current: 324/434
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• 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 7/0019 using switched or multiplexed charge circuits
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery cell balancing system is operable to utilize a relatively small number of transformers interconnected with a battery having a plurality of battery cells to selectively charge the battery cells. Windings of the transformers are simultaneously driven with a plurality of waveforms whereupon selected battery cells or groups of cells are selected and charged. A transformer drive circuit is operable to selectively vary the waveforms to thereby vary a weighted voltage associated with each of the battery cells.

Claims

1. A charge balancing method for use with a plurality of battery cells electrically connected together for balancing a charge state of a particular battery cell or a particular group of battery cells from said plurality of battery cells, said method comprising:

providing a plurality of transformers, wherein each transformer in said plurality of transformers is comprised of a primary winding and a plurality of secondary windings, wherein one of said plurality of secondary windings for each said primary winding is connected in series and comprise a group of series connected secondary windings;

operatively connecting each said group of series connected secondary windings to a distinct said particular battery cell or distinct said particular group of battery cells;

simultaneously applying a plurality of waveforms to said plurality of transformers; and

using said plurality of transformers to selectively vary said plurality of waveforms and apply a charge current to said particular battery cell or said particular group of battery cells for selectively balancing said charge state of said particular battery cell or said particular group of battery cells.

2. The method of claim 1, wherein said plurality of waveforms represent a plurality of input voltages and further comprising:

utilizing each said group of series connected secondary windings and said plurality of input voltages to produce a plurality of weighted sums of voltages for selectively balancing said charge state of said particular battery cell or said particular group of battery cells, wherein each said plurality of weighted sums of voltages is based on summing output voltages of two or more secondary windings within each group of series connected secondary windings.

3. The method of claim 1, further comprising:

providing that said plurality of transformers is fewer in number than said plurality of battery cells.

4. The method of claim 1, wherein said step of using said plurality of transformers to selectively vary said plurality of waveforms comprises selectively inverting and not inverting respective of said plurality of waveforms with respect to each other.

5. An apparatus for use with a plurality of battery cells electrically connected together, said apparatus being operable for balancing a charge state of a particular battery cell or a particular group of battery cells of said plurality of battery cells, said apparatus comprising:

a plurality of transformers wherein each transformer is comprised of;

a plurality of input windings; and

a plurality of output windings operatively connected to a distinct said particular battery cell; and

a transformer drive operably connected to each said plurality of input windings, said transformer drive being configured to simultaneously apply a plurality of waveforms to each said plurality of input windings, said transformer drive being configured to selectively vary said plurality of waveforms with respect to each other, whereby said apparatus is operable for selectively balancing said charge state of said particular battery cell or said particular group of battery,

wherein said plurality of waveforms represent a plurality of input voltages,

wherein said plurality of output windings comprise a plurality of series connected output windings that produce a plurality of weighted sums of voltages in response to said plurality of input voltages such that said plurality of weighted sums of voltages are selectively variable with respect to each other, and

wherein said plurality of weighted sums of voltages are capable of selectively balancing said charge state of said particular battery cell or said particular group of battery cells.

6. The apparatus of claim 5, wherein said plurality of transformers are fewer in number than said plurality of battery cells.

7. The apparatus of claim 5, wherein said particular battery cell comprises a first particular battery cell and a second particular battery cell, wherein said particular group of battery cells comprises a first particular group of battery cells and a second particular group of battery cells, and wherein said plurality of output windings further comprise,

a first group of output windings, said first group of output windings being connected in series to said first particular battery cell or said first particular group of battery cells, and

a second group of output windings, said second group of output windings being connected in series to said second particular battery cell or said second particular group of battery cells.

8. The apparatus of claim 7, wherein said first and second group of output windings are each associated with a different set of said plurality of input windings.

9. An apparatus for use with a plurality of battery cells electrically connected together, said apparatus being operable for balancing a charge state of a particular battery cell or a particular group of battery cells from said plurality of battery cells, said apparatus comprising:

a plurality of transformers operatively connected to said plurality of battery cells said plurality of transformers comprising a plurality of secondary windings, wherein said plurality of secondary windings comprise a plurality of series connected secondary windings operatively connected to each said particular battery cell or each said particular group of battery cells;

a transformer drive operatively connected to said plurality of transformers and being operable for simultaneously applying a plurality of waveforms to said plurality of transformers; and

a controller operable to control said transformer drive to selectively vary said plurality of waveforms for selectively balancing said charge state of said particular battery cell or said particular group of battery cells from said plurality of battery cells.

10. The apparatus of claim 9, wherein each secondary winding within each said plurality of series connected secondary windings is associated with a different said plurality of transformers.

11. The apparatus of claim 9, wherein said plurality of waveforms represent a plurality of input voltages, wherein said plurality of series connected secondary windings is operable to produce a selectively variable weighted voltage for each said particular battery cell or each said particular group of battery cells utilizing said plurality of input voltages.

12. The apparatus of claim 9, wherein said plurality of transformers are fewer in number than said plurality of battery cells.

13. The apparatus of claim 9, wherein said transformer drive is capable of producing a plurality of substantially identical waveforms which are selectively either inverted or non-inverted with respect to each other.

14. The apparatus of claim 9, wherein said transformer drive is capable of producing a plurality of waveforms which are variable in amplitude with respect to each other.