Battery system and method for sensing and balancing the charge state of battery cells

• US 8,183,870 B1
• Filed: 02/12/2009
• Issued: 05/22/2012
• 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): Assouad, Patrick
• Assistant Examiner(s): PELTON, NATHANIEL R
• Application Number:
  US12/370,021
• Time in Patent Office: 1,195 Days
• Field of Search: 324/434, 323/249, 320/118
• US Class Current: 324/434
• CPC Class Codes: H01M 10/4207 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A battery system utilizes a plurality of transformers interconnected with the battery cells. The transformers each have at least one transformer core operable for magnetization in at least a first magnetic state with a magnetic flux in a first direction and a second magnetic state with a magnetic flux in a second direction. The transformer cores retain the first magnetic state and the second magnetic state without current flow through said plurality of transformers. Circuitry is utilized for switching a selected transformer core between the first and second magnetic states to sense voltage and/or balance particular cells or particular banks of cells.

Claims

1. A battery system for a plurality of battery cells, said battery system comprising:

a plurality of transformers electrically coupled to said plurality of battery cells, said plurality of transformers comprising;

a plurality of saturable magnetic cores, said plurality of saturable magnetic cores being saturable to a first magnetic state comprising a first magnetic flux direction and being saturable to a second magnetic state comprising a second magnetic flux direction, said plurality of saturable magnetic cores being operable for substantially retaining said first magnetic state and said second magnetic state without current flow through said plurality of transformers;

a plurality of transformer selection windings connected to said plurality of saturable magnetic cores so as to be operable to address a particular transformer from said plurality of transformers through control of said first magnetic state and said second magnetic state for at least one of sensing or balancing a charge state of a particular battery cell or a particular bank of battery cells, said plurality of transformer selection windings comprising;

a plurality of row windings and a plurality of column windings for said plurality of transformers, wherein a combination of a particular row winding and a particular column winding being operable to address said particular transformer; and

a plurality of sense windings interconnected to each other in series wherein at least one sense winding is operably associated with each transformer in said plurality of transformers;

control circuitry connected to said plurality of saturable magnetic cores to supply electric current to selectively place said plurality of saturable magnetic cores in said first magnetic state or said second magnetic state for at least one of sensing or balancing said charge state of said particular battery cell or said particular bank of battery cells;

a plurality of row switches and a plurality of column switches connected to said plurality of row windings and said plurality of column windings to permit current flow through said particular row winding and said particular column winding for alternately producing said first magnetic state and said second magnetic state in said respective one of said plurality of saturable magnetic cores; and

an analog to digital converter operably connected to said plurality of sense windings for measuring said charge state of said particular battery cell or said particular bank of battery cells,

wherein said combination of said particular row winding and said articular column winding are electrically connected for alternately producing said first magnetic state and said second magnetic state in a respective one of said plurality of saturable magnetic cores for at least one of sensing or balancing said charge state of said particular battery cell or said particular bank of battery cells.

2. The battery system of claim 1 further comprising control electronics programmed to obtain a measurement of a voltage of said particular battery cell or said particular bank of battery cells from said analog to digital converter while said particular row winding and said particular column winding are alternately producing said first magnetic state and said second magnetic state in said respective one of said saturable magnetic cores.

3. The battery system of claim 1 further comprising a semiconductor connected to said particular battery cell or said particular bank of battery cells transformer to prevent leakage of charge.

4. The battery system of claim 1 further comprising at least one transformer electrically connected to a reference voltage supply to calibrate a detector of said charge state.

5. A method for monitoring a battery system comprising a plurality of transformers connected to a plurality of battery cells, said plurality of transformers being electrically connected in a plurality of groups, said plurality of transformers each comprising a transformer core, said method comprising:

operating a first group switch to set a first group of transformer cores to a first magnetic state;

operating a second group switch to set a second group of transformer cores to a second magnetic state;

operating said first group switch subsequently wherein a particular transformer core of a particular transformer located at an intersection of said first group and said second group of transformer cores changes from said second magnetic state to said first magnetic state; and

detecting a voltage of an individual battery cell or bank of battery cells connected to said particular transformer through a sense winding of said particular transformer.

6. The method of claim 5 comprising balancing said individual battery cell or bank of battery cells by repeatedly operating said first group switch and said second group switch.

7. The method of claim 6 comprising repeatedly detecting said voltage of said individual battery cell or bank of battery cells during said step of balancing.

8. The method of claim 5 comprising calibrating a voltage detector utilizing a transformer connected to a precision voltage supply.

9. A method for monitoring battery cells in a battery system comprising a plurality of transformers connected to a plurality of battery cells, said plurality of transformers being electrically connected in a plurality of groups, said plurality of transformers each comprising a transformer core, said method comprising:

operating a first group switch to set a first group of transformer cores to a first magnetic state;

operating a second group switch to set a second group of transformer cores in a to a second magnetic state;

operating said first group switch subsequently wherein only a particular transformer core of a particular transformer located at an intersection of said first group of transformer cores and said second group of transformer cores changes from said second magnetic state to said first magnetic state; and

continuing to alternately operate said first group switch and said second group switch whereby charge is added to an individual battery cell or bank of battery cells connected to said particular transformer.

10. The method of claim 9 comprising repeatedly detecting a voltage of said individual battery cell or bank of battery cells while continuing to alternately operate said first group switch and said second group switch.

11. The method of claim 10 comprising detecting said voltage with an analog to digital converter connected to sense windings of plurality of transformers.