Method and apparatus for cell monitoring and control

• US 4,871,956 A
• Filed: 02/18/1988
• Issued: 10/03/1989
• Est. Priority Date: 02/18/1988
• Status: Expired due to Term

• Current Assignee: Saft America, Inc. (Totalenergies Se)
• Original Assignee: Power Conversion, Inc.
• Inventors: Barrella, Joseph N.
• Primary Examiner(s): Hickey, R. J.
• Application Number:
  US07/158,285
• Time in Patent Office: 593 Days
• Field of Search: 320/13, 320/15, 320/18, 320/31, 320/32, 320/39, 320/48, 340/636
• US Class Current: 320/135
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• 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 7/0019 using switched or multiplexed charge circuits

Abstract

A method and apparatus for monitoring the condition of a plurality of electrochemical cells and controlling the output of said cells upon detection of a cell having a lower capacity than the others.

Claims

1. A method for monitoring the voltage of a plurality of electrochemical cells connected to an external load, and controlling the output of said cells, comprising the steps of:

(a) comparing said voltage of each cell to a reference voltage;

(b) upon detection of a predetermined difference between said cell voltage and said reference voltage, automatically disconnecting said cells from said load and automatically connecting said cells to an impedance for safe discharge, said step of comparing said voltage of each cell with said reference voltage comprising the additional steps of;

(c) storing the results of n comparisons for each cell;

(d) making an n+1 comparison between said voltage of each cell and said reference voltage; and

(e) comparing the stored results of each cell'"'"'s n comparisons to the results of its n+1 comparisons.

2. A method for monitoring and controlling the output of a plurality of electrochemical cells connected to an external load, comprising the steps of:

(a) upon the detection of a current flow, sequentially sampling and comparing the voltage of each cell to a fixed voltage reference;

(b) for each cell, storing a plurality of said comparisons;

(c) for each cell, sequentially updating the stored comparisons;

(d) for each cell, sequentially logically combining a number of stored comparisons and the most recent comparison, in order to detect a problem cell;

(e) repeatedly sampling each cell in sequence until said load is disconnected or a problem cell is detected;

(f) upon detecting a problem cell, disconnecting said cells from said load, and causing an impedance to be placed across each cell for safe discharge.

3. An apparatus for monitoring and controlling the voltage of a plurality of electrochemical cells, to which a load is selectively connected comprising:

(a) sampling switch means for sequentially connecting each cell to a comparator means;

(b) cell test sequencing means to control the sampling switch means;

(c) voltage reference means to be electronically compared in the comparator means, with the ell sequentially selected by the sampling switch means;

(d) memory means for storing a plurality of comparisons made for each cell in the comparator means;

(e) error detection means for logically combining the stored comparisons with a most recent comparison for each cell;

(f) timing means for synchronizing the operation of the cell test sequencing means, and the memory means;

(g) load switch means for disconnecting the load from the circuit upon receiving a signal from the error detection means;

(h) cell discharge means; and

(i) discharge switching means for connecting the individual cell voltages to the cell discharge means upon receiving a signal from the error detection means.