Noise reduction in an on-line battery impedance measurement system

• US 5,821,757 A
• Filed: 05/20/1997
• Issued: 10/13/1998
• Est. Priority Date: 05/20/1997
• Status: Expired due to Fees

• Current Assignee: Btech, Inc.
• Original Assignee: Btech, Inc.
• Inventors: Dob, Allan M., Alvarez, Jose A.
• Primary Examiner(s): Do, Diep N.
• Time in patent office: 511 Days
• Field of Search: 324/429, 324/430, 324/433, 324/434, 340/636, 320/218, 320/116, 320/119, 320/120, 174/113 R
• US Class Current: 324/434
• CPC Class Codes: G01R 1/06 Measuring leads; Measuring probes G01R19/145, G01R19/165 take precedence; end pieces for leads H01R11/00
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• 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: H02J 7/0021 Monitoring or indicating circuits H02J7/0026 takes precedence

Abstract

Connections between batteries and impedance measuring circuitry in a system for on-line measurement of battery cell impedance is effected by twisted wire triplets.

Claims

1. In a system for monitoring the condition a string of serially connected battery cells, the battery cells being divided into a plurality of groups of at least two adjacent cells in the string, the system including measurement circuitry, connections to the battery cells and a controllable switch coupled via conductors between the measurement circuitry and the connections, wherein the switch is controllable to couple in sucession each of the groups of battery cells to the measurement circuitry, a method for reducing induced differential currents in conductors connected between the battery cells and the switch, the method comprising the steps of:

(a) providing insulated conductors;

(b) for each of said groups of adjacent battery cells, connecting first ends of respective insulated conductors to each end of the serial string of adjacent battery cells in said each group and to each intermediate junction of the serial string of adjacent battery cells in said each group;

(c) for each of said groups of adjacent battery cells, bundling together all of the associated insulated conductors; and

(d) for each of said groups of adjacent battery cells, connecting the other ends of the associated insulated conductors to the switch;

wherein for connecting each group of adjacent battery cells to the switch there is one more associated insulated conductor than there are adjacent battery cells in said each group.

2. The method according to claim 1 wherein each of said groups of adjacent battery cells contains two battery cells and there are three insulated which are twisted together and associated with each of the two battery cells in said each group.

3. The method according to claim 2 wherein step (c) includes the step of forming approximately eight twists per foot of said insulated conductors.

4. The method according to claim 11 wherein step (c) includes the step of twisting together all of the insulated conductors associated with each of said groups of battery cells.

5. In combination with a battery system having at least one string of serially connected rechargeable battery cells and charging means connected across said at least one string for charging said battery cells, an arrangement for measuring the impedance of said battery cells without disconnecting said battery cells from said battery system, the arrangement comprising:

means for providing connections across groups of adjacent ones of said battery cells, each of said groups being within a respective single string and including at least two battery cells;

load means for conducting electrical current;

first switching means coupled between said load means and at least one predetermined point in each of said at least one string, said at least one predetermined point dividing said each string into at least two portions, there being at least one of said groups of cells within each of said portions within said each string;

second switching means coupled to said connections;

voltage measuring means coupled to said second switching means; and

control means coupled to said first and second switching means for controlling said first switching means to couple said load means in succession across each portion of said each string and for controlling said second switching means to couple said voltage measuring means in succession across each of the groups of cells within the portion of said each string to which the load means is coupled at that time;

CHARACTERIZED IN THAT;

said second switching means is coupled to said connections by a coupling arrangement comprising;

a plurality of groups of three insulated conductors, wherein the three insulated conductors in each of said groups of three insulated conductors are bundled together;

means for connecting a first end of a first insulated conductor in each of said groups of three insulated conductors to the anode of a respective first battery cell in a respective one of said groups of battery cells;

means for connecting a first end of a second insulated conductor in each of said groups of three insulated conductors to the cathode of said respective first battery cell;

means for connecting a first end of the third insulated conductor in each of said groups of three insulated conductors to the cathode of a respective second battery cell in said one group of battery cells whose anode is connected to the cathode of said respective first battery cell; and

means for connecting the second end of each insulated conductor in each of said groups of three insulated conductors to said second switching means.

6. The coupling arrangement according to claim 5 further characterized in that each of said groups of three insulated conductors are twisted together.

7. The coupling arrangement according to claim 6 further characterized in that each of said groups of three insulated conductors are twisted together with approximately eight twists per foot.