METHOD AND DEVICE FOR DIAGNOSING SECONDARY BATTERY DEGRADATION

• US 20120116701A1
• Filed: 12/10/2010
• Published: 05/10/2012
• Est. Priority Date: 03/29/2010
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Inventors: Yuasa, Shin-ichi
• Granted Patent: US 9,046,586 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/48 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 Class Codes: H01M 2220/20 Batteries in motive systems, e.g. vehicle, ship, plane
• CPC Class Codes: H01M 2220/30 Batteries in portable systems, e.g. mobile phone, laptop
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

During charging of a secondary battery, a rate of voltage change dV/dt is obtained when a voltage V of the secondary battery reaches a predetermined voltage V_pre, a charge current I for charging the secondary battery is detected, and a rate of change dQ/dt in a quantity of charged electricity Q of the secondary battery is calculated on the basis of the result of the detection. Here, the predetermined voltage V_pre is a voltage higher than a discharge cutoff voltage and lower than a charge cutoff voltage. Thereafter, a ratio X: dQ/dV, of the rate of change dQ/dt in the quantity of charged electricity to the rate of voltage change dV/dt is calculated. The calculated ratio X is compared with a reference value X_ref, and degradation of the secondary battery is determined on the basis of the result of the comparison.

Claims

1. A secondary battery life diagnosis method, comprising the steps of:

acquiring a rate of voltage change of a secondary battery during charging of the secondary battery which involves a voltage change;

acquiring a rate of change in a quantity of charged electricity of the secondary battery; and

determining degradation of the secondary battery on the basis of the rate of change in the quantity of charged electricity and the rate of voltage change.

2. A secondary battery life diagnosis method, comprising the steps of:

(a) obtaining a rate of voltage change dV/dt when a voltage V of a secondary battery reaches a predetermined voltage V_pre during charging of the secondary battery that involves a voltage change;

(b) acquiring a rate of change dQ/dt in a quantity of charged electricity Q when the voltage V of the secondary battery reaches the predetermined voltage V_pre;

(c) calculating a ratio X;

dQ/dV, of the rate of change dQ/dt in the quantity of charged electricity to the rate of voltage change dV/dt to compare the calculated ratio X with a reference value X_ref; and

(d) determining degradation of the secondary battery on the basis of the result of the comparison in step (c).

3. The secondary battery life diagnosis method according to claim 2, wherein,

the reference value X_ref is a ratio dQ/dV_int of the rate of change dQ/dt in the quantity of charged electricity to an initial value dV_int/dt for the rate of voltage change dV/dt of the secondary battery at the predetermined voltage V_pre, and

the secondary battery is determined to be degraded when the ratio X is less than or equal to α

·

(dQ/dV_int), which is a value obtained by multiplying the reference value X_ref by a proportion α

determined in accordance with the predetermined voltage V_pre.

4. The secondary battery life diagnosis method according to claim 3, further comprising the step of (e) calculating a present value QMpv of a maximum storable quantity of energy QM of the secondary battery on the basis of:

a quotient Y;

dV_int/dV, of the calculated ratio X;

dQ/dV, with respect to the reference value X_ref, dQ/dV_int, and

an initial value QM_int of the maximum storable quantity of energy of the secondary battery.

5. The secondary battery life diagnosis method according to claim 2, wherein the ratio X:

dQ/dV, is obtained for each of a plurality of the predetermined voltages V_pre different from each other.

6. The secondary battery life diagnosis method according to claim 3, wherein, when the quotient Y:

dV_int/dV, is within the range from 0.4 to 1, the present value QMpv of the maximum storable quantity of energy QM is calculated by equation QM_pv=AY+B where each of A and B is a constant.

7. The secondary battery life diagnosis method according to claim 2, wherein the secondary battery is charged by constant current charging.

8. A secondary battery degradation diagnosis device, comprising:

voltage detection means for detecting a voltage V of a secondary battery being charged;

voltage change rate calculation means for calculating a rate of voltage change dV/dt of the secondary battery when the voltage of the secondary battery detected by the voltage detection means reaches a predetermined voltage V_pre during the charging of the secondary battery;

charged electricity quantity change rate output means for outputting a rate of change dQ/dt in a quantity of charged electricity Q of the secondary battery when the voltage of the secondary battery detected by the voltage detection means reaches the predetermined voltage V_pre;

comparison means for calculating a ratio X;

dQ/dV, of the rate of change dQ/dt in the quantity of electricity to the rate of voltage change dV/dt to compare the calculated ratio X with a reference value X_ref; and

degradation determination means for determining degradation of the secondary battery on the basis of the result of the comparison by the comparison means.

9. The secondary battery degradation diagnosis device according to claim 8, further comprising calculation means for calculating a present value QMpv of a maximum storable quantity of energy QM of the secondary battery on the basis of the result of the comparison by the comparison means and an initial value QM_int of the maximum storable quantity of energy of the secondary battery.