Adaptive battery parameter extraction and SOC estimation for lithium-ion battery

Patent metadata

Field	Value
Publication number	US-9726732-B2
Application number	US-82064810-A
Country	US
Kind code	B2
Filing date	Jun 22, 2010
Priority date	Jun 22, 2010
Publication date	Aug 8, 2017
Grant date	Aug 8, 2017

Abstract

A system and method for estimating internal parameters of a lithium-ion battery to provide a reliable battery state-of-charge estimate. The method uses a two RC-pair equivalent battery circuit model to estimate the battery parameters, including a battery open circuit voltage, an ohmic resistance, a double layer capacitance, a charge transfer resistance, a diffusion resistance and a diffusion capacitance. The method further uses the equivalent circuit model to provide a difference equation from which the battery parameters are adapted, and calculates the battery parameters from the difference equation.

First claim

What is claimed is:

1. A method for estimating battery parameters of a battery, said method comprising:
reading, using a voltmeter and a current sensor electrically coupled to the battery, a measured battery voltage and a measured battery current, respectively;
calculating, using a controller in communications with the voltmeter and the current sensor, said controller including a processor and a memory, a signal vector based on the measured battery voltage and current and a previous battery voltage and current;
calculating a gain vector using the signal vector and a correlation matrix;
calculating an estimation error using the measured battery voltage and the signal vector;
adapting the battery parameters using the gain vector and the estimation error;
calculating a battery open circuit voltage and a battery resistance using the adapted battery parameters;
determining, using the controller, a battery state-of-charge using the battery open circuit voltage, including combining a voltage based state-of-charge and a current based state-of-charge using an adaptive weighting factor, where the voltage based state-of-charge is determined by a thermodynamic voltage and the current based state-of-charge is determined by Coulomb integration, and the adaptive weighting factor is adapted at each time step by an amount which is based on a validity of the battery open circuit voltage and based on a relationship between the rate of change of the voltage based state-of-charge and the rate of change of the current based state-of-charge; and
using the battery state-of-charge, by the controller, for power management of the battery, including controlling charging and discharging of the battery.

2. The method according to claim 1 wherein the method estimates six battery parameters.

3. The method according to claim 1 wherein the method estimates the battery open circuit voltage, an ohmic resistance, a double layer capacitance, a charge transfer resistance, a diffusion resistance and a diffusion capacitance.

4. The method according to claim 1 wherein the method uses a two RC-pair equivalent battery circuit model to estimate the battery parameters.

5. The method according to claim 1 wherein calculating a gain vector includes using the equation:

G
⁡

(
k
)

=

P
⁡

(

k
-
1

)

⁢

ϕ
⁡

(
k
)

λ
+

ϕ
T

⁡

(
k
)

⁢

P
⁡

(

k
-
1

)

⁢

ϕ
⁡

(
k
)

where G is the gain vector, P is the correlation matrix, Φ is the signal vector and λ is a forgetting factor.

6. The method according to claim 1 wherein calculating an estimation error includes using the equation:
α( k )= V ( k )−θ T φ( k )

where α is the estimation error, V is the measured voltage, θ is the battery parameters and Φ is the signal vector.

7. The method according to claim 1 wherein adapting the battery parameters includes using the equation:
θ( k )=θ( k− 1)+ G ( k )α( k )

where θ are the battery parameters, G is the gain vector and α is the estimation error.

8. The method according to claim 1 wherein the battery is a lithium-ion battery.

9. The method according to claim 1 wherein the battery is a vehicle battery on an electric vehicle and wherein the method is performed during operation of the vehicle.

10. A method for estimating battery parameters of a battery, said method comprising:
defining an equivalent battery circuit model of the battery that includes a battery open circuit voltage, a battery ohmic resistance, a first RC pair including a double layer capacitance and a charge transfer resistance and a second RC pair including a diffusion capacitance and a diffusion resistance;
reading, using a voltmeter and a current sensor electrically coupled to the battery, a measured battery voltage and a measured battery current, respectively;
representing, using a controller in communications with the voltmeter and the current sensor, said controller including a processor and a memory, the battery circuit model as a difference equation that includes the measured battery voltage and current and a plurality of battery parameters;
using the difference equation to determine the battery parameters that include the battery open circuit voltage, the ohmic resistance, a double layer capacitance, a charge transfer resistance, a diffusion resistance and a diffusion capacitance;
determining, using the controller, a battery state-of-charge using the battery open circuit voltage, including combining a voltage based state-of-charge and a current based state-of-charge using an adaptive weighting factor, where the voltage based state-of-charge is determined by a thermodynamic voltage and the current based state-of-charge is determined by Coulomb integration, and the adaptive weighting factor is adapted at each time step by an amount which is based on a validity of the battery open circuit voltage and based on a relationship between the rate of change of the voltage based state-of-charge and the rate of change of the current based state-of-charge; and
using the battery state-of-charge, by the controller, for power management of the battery, including controlling charging and discharging of the battery.

11. The method according to claim 10 wherein representing the battery circuit model as a difference equation includes using the equation:
V ( k )=θ 1 V ( k− 1)+θ 2 V ( k− 2)+θ 3 I ( k )+θ 4 I ( k− 1)+θ 5 I ( k− 2)+θ 6 U ( k )

where V is the measured voltage, I is the measured current, k is a time step and θ 1 , θ 2 , θ 3 , θ 4 , θ 5 and θ 6 are the battery parameters.

12. The method according to claim 10 wherein the battery is a lithium-ion battery.

Assignees

• Lin Jian
• Tang Xidong
• Koch Brian J
• Lograsso Joseph M
• Frisch Damon R
• Nabi Rezina S
• Gm Global Tech Operations Llc

Inventors

• Lin Jian
• Tang Xidong
• Koch Brian J
• Lograsso Joseph M
• Frisch Damon R
• Nabi Rezina S

Classifications

• H01M10/48

  Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte (constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569) · CPC title

• G01R31/3651

  Physics · mapped topic

• Y02T10/7044

  Cross-Sectional Technologies · mapped topic

• B60L11/1861

  Operations & Transport · mapped topic

• Y02T10/705

  Cross-Sectional Technologies · mapped topic