Method and apparatus for evaluating battery cells containing materials that exhibit voltage hysteresis

Patent metadata

Field	Value
Publication number	US-10901042-B2
Application number	US-201815934161-A
Country	US
Kind code	B2
Filing date	Mar 23, 2018
Priority date	Apr 25, 2017
Publication date	Jan 26, 2021
Grant date	Jan 26, 2021

Abstract

A method for determining a state of charge (SOC) of a rechargeable battery cell includes determining a rate-invariant charge/discharge relationship between an open-circuit voltage (OCV) and a state of charge (SOC). This includes a first finite-rate voltage scan following a reduction branch of a relationship between OCV and the SOC, and executing a second finite-rate voltage scan following an oxidation branch of a relationship between OCV and the SOC. A rate-dependent charge/discharge relationship between the OCV and the SOC is determined during scanned voltage transitions between the reduction and oxidation branches. A present SOC state is determined based upon an electrical potential, the rate-invariant charge/discharge relationship between the OCV and the SOC, and the rate-dependent charge/discharge relationship between the OCV and the SOC during a voltage-scan reversal that occurs when the scanned voltage transitions between the reduction and oxidation branches.

First claim

The invention claimed is:

1. A method for charging a battery cell of a DC power device, wherein the battery cell includes an electrode, the method comprising:
determining a rate-invariant charge/discharge relationship between an open-circuit voltage (OCV) and a state of charge (SOC) for the battery cell, including:
executing a first finite-rate voltage scan associated with a first state of dynamic equilibrium in which a scanned voltage follows a reduction branch of a relationship between the OCV and the SOC, and
executing a second finite-rate voltage scan associated with a second state of dynamic equilibrium in which the scanned voltage follows an oxidation branch of the relationship between the OCV and the SOC;

determining a rate-dependent charge/discharge relationship between the OCV and the SOC for the battery cell during a period in which the scanned voltage transitions between the reduction branch and the oxidation branch;
dynamically determining an electrical potential for the battery cell;
dynamically determining, via a controller, a present SOC state for the battery cell based upon the electrical potential for the battery cell, the rate-invariant charge/discharge relationship between the OCV and the SOC for the battery cell, and the rate-dependent charge/discharge relationship between the OCV and the SOC for the battery cell during a voltage-scan reversal that occurs when the scanned voltage transitions between the reduction and oxidation branches; and
controlling, via the controller, charging of the battery cell based upon the present SOC state for the battery cell.

2. The method of claim 1 , further comprising determining the electrical potential for the battery cell (U) in relation to the SOC for the battery cell (x) in accordance with the relationship:

U
=

U
avg

⁡

(
x
)

+

U

ma
⁢

⁢
x

⁡

(
x
)

⁢
ϛ

,

-
1

≤
ϛ
≤
1

U
avg

⁡

(
x
)

=

U
1

⁡

(
x
)

+

U
0

⁡

(
x
)

2

,

U

ma
⁢

⁢
x

⁡

(
x
)

=

U
1

⁡

(
x
)

-

U
0

⁡

(
x
)

2

;

wherein the rate-dependent charge/discharge relationship between the OCV and the SOC for the battery cell during the voltage-scan reversal is determined in accordance with the relationship:



tanh
⁡

(

α
x

⁢

dx
dt

)



<
0.97

and,
wherein the rate-invariant charge/discharge relationship between the OCV and the SOC for the battery cell during the voltage-scan reversal is determined in accordance with the relationship:



tanh
⁡

(

α
x

⁢

dx
dt

)



≥
0.97

wherein:
α represents a fitting factor in relation to a stress function ,
x represents the SOC, and
t represents time.

3. The method of claim 2 , further comprising indicating a change in the stress function in relation to time in accordance with the relationship:

d
⁢

⁢
ϛ

Assignees

• Gm Global Tech Operations Llc

Inventors

• Verbrugge Mark W
• Baker Daniel R
• Xiao Xingcheng

Classifications

• H02J7/94

  in response to battery current · CPC title

• H02J7/82

  Control of state of charge [SOC] · CPC title

• G01R31/367

  Software therefor, e.g. for battery testing using modelling or look-up tables · CPC title

• G01R31/3835 Primary

  involving only voltage measurements · CPC title

• Y02E60/10

  Energy storage using batteries · CPC title