METHOD OF ESTIMATING STATE OF CHARGE OF SECONDARY CELL, STATE-OF-CHARGE ESTIMATION DEVICE, CELL PACK, ELECTRONIC APPARATUS, AND ELECTRIC VEHICLE

• US 20130317697A1
• Filed: 05/21/2013
• Published: 11/28/2013
• Est. Priority Date: 05/28/2012
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Hotta, Shin
• Granted Patent: US 9,581,650 B2
• Time in Patent Office: Days
• US Class Current: 701/34.4
• CPC Class Codes: B60L 2240/545 Temperature
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 2240/549 Current
• CPC Class Codes: B60L 2260/44 by parameter estimation
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/382 Arrangements for monitoring battery or accumulator variables, e.g. SoC
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A method of estimating a state of charge of a secondary cell includes: calculating a value of (∂E_emf/∂T) in advance on the assumption that E_emf is an electromotive force of the secondary cell and T is a temperature of the secondary cell; and calculating the state of charge based on at least a value of (∂E_emf/∂T) for which a value of the state of charge is set as a variable, a temperature measurement value of the secondary cell, and a current measurement value of the secondary cell.

Claims

1. A method of estimating a state of charge of a secondary cell, comprising:

calculating a value of (∂

E_emf/∂

T) in advance on the assumption that E_emf is an electromotive force of the secondary cell and T is a temperature of the secondary cell; and

calculating the state of charge based on at least a value of (∂

E_emf/∂

T) for which a value of the state of charge is set as a variable, a temperature measurement value of the secondary cell, and a current measurement value of the secondary cell.

2. The method of estimating a state of charge of a secondary cell according to claim 1, wherein the state of charge is calculated not only based on the value of (∂

E_emf/∂

T) for which the value of the state of charge is set as the variable, the temperature measurement value of the secondary cell, and the current measurement value of the secondary cell but also based on an internal resistance value of the secondary cell.

3. The method of estimating a state of charge of a secondary cell according to claim 1, further comprising:

calculating a state of charge at time t₁ based on a state of charge at time t₀ and a current measurement value of the secondary cell from time t₀ to time t₁; and

correcting the state of charge at time t₀ so that an absolute value Δ

T_diff (=|Δ

T_real−

Δ

T_calc|) of a difference between an actual measurement temperature increase amount Δ

T_real based on the temperature measurement value of the secondary cell from time t₀ to time t₁ and a calculated temperature increase amount Δ

T_calc of the secondary cell from time t₀ to time t₁, which is calculated based on at least the value of (∂

E_emf/∂

T) for which the value of the state of charge is set as the variable, the temperature measurement value of the secondary cell, and the current measurement value of the secondary cell, becomes a second predetermined value (where the second predetermined value<

a first predetermined value), when the absolute value Δ

T_diff exceeds the first predetermined value.

4. The method of estimating a state of charge of a secondary cell according to claim 1, wherein, when a temperature change of the secondary cell is equal to or less than a temperature measurement limit of a temperature measurement device and an open voltage change of the secondary cell is equal to or less than a voltage measurement limit of a voltage measurement device, an open voltage of the secondary cell is measured by the voltage measurement device, the temperature of the secondary cell is measured by the temperature measurement device, and the value of (∂

E_emf/∂

T) is calculated based on the open voltage measurement result and the temperature measurement result.

5. The method of estimating a state of charge of a secondary cell according to claim 1,

wherein the secondary cell includes a lithium-ion secondary cell, and

wherein, in a state in which a diffusion reaction of lithium ions does not occur, an open voltage of the secondary cell is measured by a voltage measurement device, the temperature of the secondary cell is measured by the temperature measurement device, and the value of (∂

E_emf/∂

T) is calculated based on the open voltage measurement result and the temperature measurement result.

6. The method of estimating a state of charge of a secondary cell according to claim 5, wherein the state in which the diffusion reaction of lithium ions does not occur is a state in which a temperature change of the secondary cell is equal to or less than a temperature measurement limit of the temperature measurement device and an open voltage change of the secondary cell is equal to or less than a voltage measurement limit of the voltage measurement device.

7. The method of estimating a state of charge of a secondary cell according to claim 4, wherein the voltage measurement device having the voltage measurement limit of 1×

10<sup>−

6</sup> volts and the temperature measurement device having the temperature measurement limit of 1×

10<sup>−

2</sup>°

C. are used.

8. A state-of-charge estimation device that calculates a state of charge of a secondary cell, comprising:

a storage unit that stores a value of (∂

E_emf/∂

T) on the assumption that E_emf is an electromotive force of the secondary cell and T is a temperature of the secondary cell;

a temperature measurement device that measures the temperature of the secondary cell;

a current measurement device that measures a current of the secondary cell; and

an arithmetic device that calculates the state of charge based on at least the value of (∂

E_emf/∂

T) for which a value of the state of charge is set as a variable, a temperature measurement value of the secondary cell, and a current measurement value of the secondary cell.

9. A cell pack comprising:

a secondary cell; and

a state-of-charge estimation device that calculates a state of charge of the secondary cell,

wherein the state-of-charge estimation device includes

a storage unit that stores a value of (∂

E_emf/∂

T) on the assumption that E_emf is an electromotive force of the secondary cell and T is a temperature of the secondary cell,

a temperature measurement device that measures the temperature of the secondary cell,

a current measurement device that measures a current of the secondary cell, and

an arithmetic device that calculates the state of charge based on at least the value of (∂

E_emf/∂

T) for which a value of the state of charge is set as a variable, a temperature measurement value of the secondary cell, and a current measurement value of the secondary cell.

10. An electronic apparatus comprising:

a secondary cell; and

a cell pack that includes a state-of-charge estimation device calculating a state of charge of the secondary cell,

wherein the state-of-charge estimation device includes

a storage unit that stores a value of (∂

E_emf/∂

T) on the assumption that E_emf is an electromotive force of the secondary cell and T is a temperature of the secondary cell,

a temperature measurement device that measures the temperature of the secondary cell,

a current measurement device that measures a current of the secondary cell, and

an arithmetic device that calculates the state of charge based on at least the value of (∂

E_emf/∂

T) for which a value of the state of charge is set as a variable, a temperature measurement value of the secondary cell, and a current measurement value of the secondary cell.

11. An electric vehicle comprising:

a secondary cell; and

a cell pack that includes a state-of-charge estimation device calculating a state of charge of the secondary cell,

wherein the state-of-charge estimation device includes

a storage unit that stores a value of (∂

E_emf/∂

T) on the assumption that E_emf is an electromotive force of the secondary cell and T is a temperature of the secondary cell,

a temperature measurement device that measures the temperature of the secondary cell,

a current measurement device that measures a current of the secondary cell, and

an arithmetic device that calculates the state of charge based on at least the value of (∂

E_emf/∂

T) for which a value of the state of charge is set as a variable, a temperature measurement value of the secondary cell, and a current measurement value of the secondary cell.