Method for estimating the state of health of an electrochemical cell for storing electrical energy

• US 11,143,709 B2
• Filed: 05/26/2014
• Issued: 10/12/2021
• Est. Priority Date: 06/04/2013
• Status: Active Grant

• Current Assignee: Renault Sas (Renault)
• Original Assignee: Renault Sas (Renault)
• Inventors: Delobel, Bruno, Saint-Marcoux, Antoine
• Primary Examiner(s): Rastovski, Catherine T.
• Assistant Examiner(s): Liang, Leonard S
• Application Number:
  US14/895,565
• Publication Number:
  US 20160154063A1
• Time in Patent Office: 2,696 Days
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health
• 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

Abstract

A method for estimating a state of health of an electrochemical cell for storing electrical energy includes applying at least one current strength peak to the cell, the current peak passing through the cell, measuring a variation, as a function of a time t elapsed after the application of the current peak, of voltage U at the terminals of the cell, and calculating at least one coefficient α_I1 and at least one coefficient U_0,I1 such that the function √{square root over (t)}→α_I1×√{square root over (t)}+U_0,I1 is a linear approximation of the variation of the voltage U as a function of √{square root over (t)} for √{square root over (t)}≥C, where C>0. The method is used in electrical or hybrid vehicles.

Claims

1. A method for estimating a state of health of an electrochemical cell for storing electrical energy, the method comprising:

applying to the cell at least one current peak of intensity I₁, the current peak flowing through the cell;

measuring a variation, as a function of a time t that has passed after an application of the current peak, of a voltage U across terminals of the cell;

calculating at least one coefficient α

_I1 and at least one coefficient U_0,I1 such that U=α

_I1×

√

{square root over (t)}+U_0,I1 is a linear approximation of the variation of the voltage U as a function of √

{square root over (t)}, where √

{square root over (t)}≥

1;

calculating a coefficient β

such that −

U/√

{square root over (t)}=β

×

I is a linear approximation of a variation of Δ

U/√

{square root over (t)} as a function of I, wherein a plurality of current peaks of intensities (I_n)<sub>n≥

2</sub> are applied to the cell (I₁, I₂, I₃, I₄, I₅);

estimating the state of health of the cell based on either of the coefficients calculated in the calculating; and

detecting a fault with connection hardware of the cell when at least one of the coefficients is increasing above a predetermined amount with respect to a value of the coefficient at a beginning of life of the cell.

2. The method as claimed in claim 1, wherein, the coefficients α

_I1 and U_0,I1 having been calculated a first time at the beginning of life of the cell, the method further comprises;

calculating a ratio of a value currently calculated of α

_I1 with respect to its value calculated at the beginning of life, an increase of the coefficient α

_I1 beyond a predetermined value of said ratio indicating an incapacity of the cell to deliver a current, and/or;

calculating a ratio of a value currently calculated of U_0,I1 with respect to its value calculated at the beginning of life, an increase in the coefficient U_0,I1 beyond a predetermined value of said ratio indicating an incapacity of the cell to deliver the current.

3. The method as claimed in claim 1, wherein, tables or graphs of aging having been filled out beforehand, the method further comprises:

comparing a value currently calculated of α

_I1 with values contained in a table or a graph of aging associating levels of aging with values of α

_I1, in such a manner as to deduce a level of aging of the cell, and/or;

comparing a value currently calculated of U_0,I1 with values contained in a table or a graph of aging associating levels of aging with values of U_0,I1, in such a manner as to deduce the level of aging of the cell.

4. The method as claimed in claim 1, wherein, the coefficient β

having been calculated a first time at the beginning of life of the cell, the method further comprises;

calculating a ratio of a value currently calculated of β

with respect to its value calculated at the beginning of life, an increase in the coefficient β

beyond a predetermined value of said ratio indicating an incapacity of the cell to deliver a current.

5. The method as claimed in claim 1, wherein, tables or graphs of aging having been filled out beforehand, the method further comprises:

comparing a value currently calculated of β

with values contained in a table or a graph of aging associating levels of aging with values of β

, in such a manner as to deduce the level of aging of the cell.

6. The method as claimed in claim 1, further comprising:

calculating a coefficient γ

such that −

U_0,I1=γ

×

I+OCV, where OCV is an open circuit voltage of the cell, is a linear approximation of the variation of U_0,I as the function of I.

7. The method as claimed in claim 6, wherein, the coefficient γ

having been calculated a first time at the beginning of life of the cell, the method further comprises;

calculating a ratio of a value currently calculated of γ

with respect to its value calculated at the beginning of life of the cell, an increase in the coefficient γ

beyond a predetermined value of said ratio indicating an incapacity of the cell to deliver a current.

8. The method as claimed in claim 7, wherein, tables or graphs of aging having been filled out beforehand, the method further comprises:

comparing the value currently calculated of γ

with values contained in a table or a graph of aging associating levels of aging with values of γ

, in such a manner as to deduce the level of aging of the cell.