Battery cell grading holder

• US 6,191,591 B1
• Filed: 05/29/1998
• Issued: 02/20/2001
• Est. Priority Date: 05/29/1998
• Status: Expired due to Fees

• Current Assignee: Congress Financial Corporation (Wells Fargo & Company)
• Original Assignee: Moltech Power Systems Incorporated (City of Shanghai)
• Inventors: Delgado, Julio, Coyle, Harold T., Ratajczak, Joseph S., Rockett, Danny F.
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): Deb, Anjan K
• Application Number:
  US09/087,550
• Time in Patent Office: 998 Days
• Field of Search: 324/434, 324/435, 324/437, 324/450, 429/90-93, 429/100, 429/6, 429/7, 429/97-99, 429/61, 429/62, 320/116, 320/156, 320/161, 320/162, 320/122
• US Class Current: 324/437
• CPC Class Codes: G01R 1/0408 Test fixtures or contact fields; Connectors or connecting adaptors; Test clips; Test sockets G01R1/067 takes precedence; mass production testing systems G01R31/59; testing of connections G01R31/66; for testing printed circuit boards G01R31/2808
• CPC Class Codes: G01R 31/36 Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
• CPC Class Codes: G01R 31/3835 involving only voltage measurements

Abstract

A cell grading test fixture includes an array of cell sockets electrically interconnected in series so that current through the entire array of cells flows through each of the cells once inserted into the fixture. Associated with each socket is an indicator which indicates to the operator when a cell voltage has fallen to a predetermined level. Each socket of the test fixture includes a spring-loaded switch contact such that upon removal of a cell which has dropped below a threshold voltage, the movable contact engages the contact of an adjacent socket, shorting out the cell location such that the series circuit of cells continues to provide a current path for the remaining cells.

Claims

1. A test fixture for grading battery cells comprising:

an array of cell-receiving sockets for receiving individual cells;

an indicator associated with each socket; and

an electrical circuit coupled to each of said sockets and said associated indicators for activating an indicator when the voltage of a cell inserted into the socket associated with said indicator reaches a predetermined level;

said electrical circuit including an electrical contact for each socket, said contact comprising fixed and movable sections, said contact mounted to said socket such that when a cell is removed from said socket, said movable contact section moves to complete said electrical circuit.

2. The test fixture as defined in claim 1 wherein said indicator is a light.

3. The test fixture as defined in claim 2 wherein said light is an LED.

4. The test fixture as defined in claim 1 wherein each of said sockets include a cell-receiving recess and said electrical circuit includes a contact mounted to each socket, each of said contacts comprising a generally L-shaped member having a vertically extending fixed contact extending into said recess and a generally horizontally extending movable contact.

5. The test fixture as defined in claim 4 wherein said movable contact engages the fixed contact of an adjacent socket when a cell is removed to complete the circuit vacated by the cell.

6. The test fixture as defined in claim 5 wherein said contact is made of a resilient conductive material.

7. The test fixture as defined in claim 4 wherein said contact is made of beryllium copper.

8. The test fixture as defined in claim 7 wherein each of said sockets are made of a polymeric material.

9. The test fixture as defined in claim 1 wherein said circuit includes a plurality of comparator circuits, each copnarator circuit coupled to one of said sockets, and a reference voltage source coupled to each of said comparators such that each comparator circuit compares the voltage of said reference voltage source and the voltage of a cell inserted into the socket coupled to the comparator circuit.

10. The test fixture as defined in claim 9 wherein said indicator is an LED coupled to each comparator and illuminated by signal from said comparator when a cell voltage falls below a predetermined reference level.

11. A test fixture for grading battery cells comprising:

an array of cell-receiving sockets for receiving individual cells, each of said sockets including an insert having a recess shaped to receive a corresponding cell shape;

an indicator associated with each socket; and

an electrical circuit coupling each of said sockets in series with one another and coupled to said associated indicators for activating an indicator when the voltage of a cell inserted into the socket associated with said indicator falls below a predetermined level; and

each of said sockets also includes an electrical switch contact with a movable element to close the circuit past the socket when a cell is removed from said socket.

12. The test fixture as defined in claim 11 wherein said movable element engages one terminal of a cell inserted into the socket and the contact of an adjacent socket when the cell is removed.

13. The test fixture as defined in claim 12 wherein said contact is made of a resilient conductive material.

14. The test fixture as defined in claim 13 wherein said contact is made of beryllium copper.

15. The test fixture as defined in claim 14 wherein said array of sockets is made of a polymeric material.

16. The test fixture as defined in claim 11 wherein said electrical circuit includes a plurality of comparator circuits coupled to each of said cells and a reference voltage source coupled to each of said comparators for comparing the voltage between said reference voltage source and each of said cells.

17. The test fixture as defined in claim 16 wherein said indicator is coupled to said comparator for providing a visual indication when the comparator detects that the cell voltage falls below the predetermined reference voltage.

18. The test fixture as defined in claim 11 wherein said indicator includes an LED coupled to each comparator and illuminated by a signal from said comparator when a cell voltage falls below a predetermined reference level.

19. A method of grading a plurality of individual cells comprising the steps of:

positioning the cells in a test fixture with an array of sockets which include contacts which couple the cells in series when the cells are in position and which short out an individual socket when a cell is removed therefrom;

applying a load to said cells for drawing current therefrom;

coupling an electrical circuit to each of said cells for determining when the cell falls below a predetermined threshold voltage;

providing a visual indication adjacent each cell when such threshold is reached;

removing a cell when it has reached said threshold voltage; and

noting the time at which each cell in the fixture has reached its predetermined threshold voltage.

20. A test fixture for grading battery cells comprising:

an array of sockets for receiving individual cells, each socket including a cell-receiving block having a contact mounted thereto, said block including a recess, a contact-receiving member, a cell-receiving recess, a contact-holding member and a floor with an opening for receiving a contact element therethrough; and

a contact comprising fixed and movable elements, said contact mounted to said block with said fixed element positioned adjacent said cell-receiving aperture and said movable element extending outwardly from said mounting block to engage a cell through an opening in the floor of an adjacent socket of the test fixture and short out an individual socket when a cell is removed.

21. The test fixture as defined in claim 20 wherein each of said contacts comprises a generally L-shaped member having a vertically extending fixed element and a generally horizontally extending movable element with a base extending therebetween.

22. The test fixture as defined in claim 21 wherein said fixed contact element includes a contact corner at the junction of said base and said vertically extending contact element which is engaged by said movable contact element of an adjacent socket.

23. The test fixture as defined in claim 22 wherein said movable contact element comprises a generally U-shaped member mounted to said base of said socket and including a central section for engaging the center terminal of a cell.

24. The test fixture as defined in claim 23 wherein said movable contact element further includes an extension and a downwardly projecting end for engaging said contact corner of an adjacent socket when a cell is removed from the adjacent socket.

25. The test fixture as defined in claim 24 wherein said contact is made of a resilient conductive material.

26. The test fixture as defined in claim 25 wherein said contact is made of beryllium copper.

27. A test fixture for grading electrochemical cells comprising:

a support structure having an array of apertures for receiving electrochemical cells; and

a plurality of electrical conductors each having a fixed contact pad and a movable contact pad, each of said conductors being mounted to said support structure such that said fixed contact pad extends within one of said apertures to contact a first contact terminal of a cell inserted into that aperture and such that said movable contact extends into an adjacent aperture to contact a second tenninal of a cell inserted into the adjacent aperture and to contact a fixed contact pad of an adjacent conductor when a cell is not inserted in the adjacent aperture.