Method and apparatus for estimating a state of health of a battery pack and computer-readable medium

Patent metadata

Field	Value
Publication number	US-10620273-B2
Application number	US-201815992371-A
Country	US
Kind code	B2
Filing date	May 30, 2018
Priority date	May 31, 2017
Publication date	Apr 14, 2020
Grant date	Apr 14, 2020

Abstract

A method and apparatus for estimating a state of health of a battery pack and a computer-readable medium are provided, the method including: detecting changes of health indicators of every battery unit in the battery pack, determining whether the battery unit has a correction opportunity for a state of charge thereof during a predetermined period of time based on the detected changes of the health indicators, calculating corrected states of charge and one or more of cumulative changes in capacity between every two correction opportunities of a battery unit having two or more correction opportunities, obtaining a first estimated state of health of the battery unit having two or more correction opportunities based on the above data and estimating the state of health of the battery pack based on the first estimated state of health of the battery unit having two or more correction opportunities.

First claim

What is claimed is:

1. A method for estimating a state of health of a battery pack, comprising:
detecting changes of health indicators of a battery unit in the battery pack during charging or discharging processes, wherein the health indicators comprise a voltage between two terminals of the battery unit, a charging current or a discharging current of the battery unit, and a temperature of the battery unit;
determining whether the battery unit has a correction opportunity for a state of charge thereof during a predetermined period of time for estimating the state of health of the battery pack based on the detected changes of the health indicators, wherein the correction opportunity for the battery unit is when the battery unit is sat quietly for a long period of time or when the battery unit is fully charged;
selecting, from the battery pack, a battery unit having two or more correction opportunities as a first battery unit and calculating corrected states of charge at any two of the correction opportunities of the first battery unit and a cumulative change in capacity between the two correction opportunities of the first battery unit; and
obtaining a first estimated state of health of the first battery unit based on the cumulative change in capacity between the two correction opportunities and the corrected states of charge at the two correction opportunities, and estimating the state of health of the battery pack based on the first estimated state of health of the first battery unit.

2. The method of claim 1 , wherein after the obtaining a first estimated state of health of the first battery unit based on the cumulative change in capacity between the two correction opportunities and the corrected states of charge at the two correction opportunities, and estimating the state of health of the battery pack based on the first estimated state of health of the first battery unit, the method further comprises:
correcting a state of health estimation curve of the battery pack based on the estimated state of health of the battery pack, wherein the state of health estimation curve of the battery pack is represented by a function of

S
⁢

⁢
O
⁢

⁢
H
⁢

⁢
C

=

1

2
⁢
A
×

e

(

-

E
+

K
×

C
Rate
0.2

R
×
T

)

×
t

+

c
0

,

 wherin “SOHC” represents the state of health of the battery pack, “E”, “A” and “K” are battery cell related parameters, C Rate is a cumulative cyclic capacity of the battery pack, “T” is a temperature of the battery pack, “R” and “c 0 ” are constants, and “t” is a duration in which the battery pack is used.

3. The method of claim 1 , wherein before the obtaining a first estimated state of health of the first battery unit based on the cumulative change in capacity between the two correction opportunities and the corrected states of charge at the two correction opportunities, and estimating the state of health of the battery pack based on the first estimated state of health of the first battery unit, the method further comprises:
determining whether a difference between the corrected states of charge at the two correction opportunities is larger than a predetermined value.

4. The method of claim 3 , wherein the obtaining a first estimated state of health of the first battery unit based on the cumulative change in capacity between the two correction opportunities and the corrected states of charge at the two correction opportunities, and estimating the state of health of the battery pack based on the first estimated state of health of the first battery unit comprises:
SOHC( n )=ΔCapacity( n )/{SOC( n )×BOL Capacity( n )}

wherein SOHC (n) is the first estimated state of health of the first battery unit “n”, ΔCapacity (n) is the cumulative change in capacity between the two correction opportunities of the first battery unit “n”, SOC (n) is the corrected state of charge at one of the two correction opportunities corresponding to the cumulative change in capacity of the first battery unit “n”, and BOL Capacity (n) is a preset initial cumulative change in capacity of the first battery unit “n”.

5. The method of claim 2 , wherein the correcting a state of health estimation curve of the battery pack based on the estimated state of health of the battery pack comprises:
obtaining a correction factor “a” based on an average value SOHC k-Average of the first estimated state of health, which is calculated at the k th time, of the battery unit and the state of health SOHC k-1 , which is calculated based on the state of health estimation curve being corrected (k−1) times of the battery pack, of the battery pack;
correcting the state of health estimation curve being corrected (k−1) times of the battery pack by the correction factor “a”, wherein
an expression for calculating the correction factor “a” is the following:
a =SOHC k-Average ÷SOHC k-1

wherein “k” is an integer larger than zero.

6. The method of claim 2 , further comprising:
if a battery unit in the battery pack does not have any correction opportunity or has only one correction opportunity during the predetermined period of time for estimating the state of health of the battery pack, then estimating the state of health SOHC Estimated of the battery pack based on an initial state of health estimation curve and a corrected initial state of health estimation curve, wherein
SOHC Estimated =SOHC p (m-1) −SOHC attenuation value,

SOHC attenuation value=SOHC m-1 −SOHC m ,

SOHC m is obtained based on x m and a function of the state of health estimation curve that is corrected for the last time before a m th predetermined period of time, and x m is operating condition data from a start time of estimating the state of health of the battery pack to the end of the m th predetermined period of time;
if a batte

Assignees

• Contemporary Amperex Technology Co Ltd

Inventors

• Tang Shenzhi
• Lu Yanhua

Classifications

• G01R31/382 Primary

  Arrangements for monitoring battery or accumulator variables, e.g. SoC · CPC title

• G01R31/392 Primary

  Determining battery ageing or deterioration, e.g. state of health · CPC title

• G01R31/3646

  for indicating electrical conditions or variables, e.g. visual or audible indicators · CPC title

• G01R31/3648

  comprising digital calculation means, e.g. for performing an algorithm · CPC title

• G01R31/385

  Arrangements for measuring battery or accumulator variables (for monitoring G01R31/382) · CPC title