Battery capacity calculating method

• US 20040160224A1
• Filed: 01/14/2004
• Published: 08/19/2004
• Est. Priority Date: 05/14/2002
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Yamazaki, Kazuo, Tomita, Takashi, Hori, Masanori, Ikeda, Tamon, Hatazawa, Tsuyonobu, Ishikawa, Yuuichi, Nawa, Ryuichi
• Granted Patent: US 7,091,698 B2
• Time in Patent Office: Days
• US Class Current: 324/426
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

The present invention is relative to a battery capacity calculating method including a reference discharge curve calculating step of finding a discharge curve, operating as a reference, a corrected voltage calculating step of correcting a measured voltage V1 of the battery with a component of an electrical resistance to find a corrected voltage V, and a capacity calculating step of finding the discharging capacity of the battery from the discharge curve, operating as a reference, using the corrected voltage V. The capacity calculating step includes a sub-step of calculating a capacity deterioration index S, as a ratio of capacity decrease caused by battery deterioration. The discharging capacity, calculated from the discharging capacity, operating as a reference, using the corrected voltage V, is further multiplied with the capacity deterioration index S to calculate the discharging capacity.

Claims

1. A method for measuring the capacity of a battery comprising:

a step of calculating a reference discharge curve for finding a discharge curve operating as a reference;

a correction voltage calculating step of correcting a measured voltage V1 of the battery by a resistance component of the battery to find a corrected voltage V; and

a capacity calculating step of calculating the discharging capacity of the battery from said discharge curve, operating as reference, using said corrected voltage V.

2. The method for measuring the battery capacity according to claim 1 wherein said discharge curve, operating as reference, is found on the basis of a measured value of the battery in an initial state.

3. The method for measuring the battery capacity according to claim 1 wherein said discharge curve, operating as reference, is found on the basis of a theoretical value or a measured value as found from the difference between an open circuit potential function of a cathode and an open circuit potential function of an anode.

4. The method for measuring the battery capacity according to claim 1 wherein, with a voltage derived from an internal resistance of the battery of V2, a current dependent resistance derived voltage of V3 and a voltage dependent resistance derived voltage of V4, said corrected voltage V is represented by the following equation:

corrected voltage V=V1+Σ

Vn

where n≧

2, and V2≦

0, V3≦

0 and V4≦

0 if measurement is made during charging, while V2≧

0, V3≧

0 and V4≧

0 if measurement is made during discharging.

5. The method for measuring the battery capacity according to claim 4 wherein the voltage derived from an internal resistance of the battery V2 is equivalent to a voltage drop IR as found from a load current I and the internal resistance R of the battery.

6. The method for measuring the battery capacity according to claim 4 wherein the current dependent resistance derived voltage of V3 may be obtained on the basis of the Butler-Bolmer theory and/or the Nernst'"'"'s marginal diffusion theory.

7. The method for measuring the battery capacity according to claim 4 wherein the voltage dependent resistance derived voltage V4 is found on the basis of the resistance against ion drift ascribable to the gradient of an electrical field in an electrolytic solution.

8. The method for measuring the battery capacity according to claim 1 wherein said capacity calculating step includes a sub-step of calculating a capacity deterioration index S representing the ratio of capacity decrease due to deterioration of said battery;

said capacity calculating step calculating the discharging capacity by multiplying the discharging capacity, calculated from said discharge curve, operating as reference, with the use of said corrected voltage V, with said capacity deterioration index S.

9. The method for measuring the battery capacity according to claim 8 wherein the charging capacity across two or more voltage points is measured to find a first charging capacity, a voltage derived from an internal resistance of the battery V2, as measured during charging based on the voltage drop in case of performing pulse charging at the time of charging, is found, a second charging capacity is found by calculating the charging capacity from a charging curve derived from said discharge curve, operating as a reference, using a corrected voltage V across two or more voltage points, as corrected by the voltage derived from the internal resistance of the battery V2, and wherein the ratio of said first and second charging capacities is taken to calculate said capacity deterioration index S.

10. The method for measuring the battery capacity according to claim 8 wherein the discharging capacity across two or more voltage points is measured to find a first discharging capacity, a voltage derived from an internal resistance of the battery V2, as measured during discharging based on the voltage drop in case of performing pulse discharging at the time of discharging, is found, a second discharging capacity is found by calculating the discharging capacity from said discharge curve, operating as a reference, using a corrected voltage V across two or more voltage points, as corrected by a voltage derived from the internal resistance of the battery V2, and wherein the ratio of said first and second discharging capacities is taken to calculate said capacity deterioration index S.