SECONDARY-BATTERY LIFE ESTIMATION APPARATUS AND METHOD

• US 20090070052A1
• Filed: 09/03/2008
• Published: 03/12/2009
• Est. Priority Date: 09/07/2007
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Iida, Takuma, Taniguchi, Akihiro
• Granted Patent: US 8,060,323 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery

Abstract

A secondary-battery life estimation apparatus includes: a voltage measuring portion measuring a terminal voltage of a secondary battery to be measured; a first memory storing in advance a terminal voltage V₀ of a non-degraded secondary battery before the non-degraded secondary battery discharges after fully charged; a second memory which stores in advance a life-estimation data map as a look-up table associating a voltage difference dV between a terminal voltage V of the secondary battery to be measured before the secondary battery to be measured discharges after fully charged and the terminal voltage V₀ with a residual life of the secondary battery to be measured; and a CPU calculating the voltage difference dV between the terminal voltage V measured by the voltage measuring portion before the secondary battery to be measured discharges after fully charged and the terminal voltage V₀ stored in the first memory and estimating the residual life of the secondary battery to be measured based on the life-estimation data map stored in the second memory using the voltage difference dV.

Claims

1. A secondary-battery life estimation apparatus, comprising:

a voltage measuring portion measuring a terminal voltage of a secondary battery to be measured;

a first memory storing in advance a terminal voltage V₀ of a non-degraded secondary battery before the non-degraded secondary battery discharges after fully charged;

a second memory which stores in advance a life-estimation data map as a look-up table associating a voltage difference dV between a terminal voltage V of the secondary battery to be measured before the secondary battery to be measured discharges after fully charged and the terminal voltage V₀ with a residual life of the secondary battery to be measured; and

a CPU calculating the voltage difference dV between the terminal voltage V measured by the voltage measuring portion before the secondary battery to be measured discharges after fully charged and the terminal voltage V₀ stored in the first memory and estimating the residual life of the secondary battery to be measured based on the life-estimation data map stored in the second memory using the voltage difference dV.

2. The secondary-battery life estimation apparatus according to claim 1, wherein the CPU allows the voltage measuring portion to measure the terminal voltage V when a preset time elapses for stabilizing the terminal voltage of the secondary battery to be measured since this secondary battery is fully charged and before the secondary battery discharges.

3. The secondary-battery life estimation apparatus according to claim 1, further comprising a temperature measuring portion measuring a temperature of the secondary battery to be measured, wherein:

the life-estimation data map is a look-up table associating the voltage difference dV and the temperature of the secondary battery to be measured with the residual life of the secondary battery to be measured; and

the CPU estimates the residual life of the secondary battery to be measured by acquiring the residual life associated with the calculated voltage difference dV and the temperature measured by the temperature measuring portion in the life-estimation data map stored in the second memory.

4. The secondary-battery life estimation apparatus according to claim 1, wherein the life-estimation data map is a look-up table indicating that the wider the voltage difference dV becomes, the shorter the residual life becomes.

5. The secondary-battery life estimation apparatus according to claim 3, wherein the life-estimation data map is a look-up table indicating that the wider the voltage difference dV becomes, the shorter the residual life becomes, and the wider the difference between the temperature of the secondary battery to be measured and a predetermined reference temperature, the longer the residual life becomes.

6. The secondary-battery life estimation apparatus according to claim 5, wherein the secondary battery is a nickel-hydrogen secondary battery.

7. The secondary-battery life estimation apparatus according to claim 1, wherein the secondary battery is a battery block formed by a plurality of cells.

8. The secondary-battery life estimation apparatus according to claim 7, wherein:

a plurality of the secondary batteries are combined into a secondary-battery module;

the voltage measuring portion measures each terminal voltage of the plurality of secondary batteries; and

the CPU estimates each residual life of the plurality of secondary batteries and estimates the life of the secondary-battery module at the shortest of the estimated residual lives.

9. The secondary-battery life estimation apparatus according to claim 1, further comprising a charge-and-discharge controller which charges the secondary battery fully by charging the secondary battery with a charging current supplied at a preset first current value, charging the secondary battery with a charging current reduced to a second current value smaller than the first current value when the terminal voltage of the secondary battery measured by the voltage measuring portion becomes a full-charge voltage, and further charging the secondary battery for a predetermined charging set time with a charging current reduced to a third current value smaller than the second current value when the terminal voltage of the secondary battery measured by the voltage measuring portion becomes the full-charge voltage again.

10. The secondary-battery life estimation apparatus according to claim 1, further comprising:

a temperature measuring portion measuring a temperature of the secondary battery to be measured; and

a charge-and-discharge controller which charges the secondary battery fully by charging the secondary battery with a charging current supplied at a preset first current value, charging the secondary battery with a charging current reduced to a second current value smaller than the first current value when the terminal voltage of the secondary battery measured by the voltage measuring portion becomes a full-charge voltage, and further charging the secondary battery for a predetermined charging set time with a charging current reduced to a third current value smaller than the second current value when the terminal voltage of the secondary battery measured by the voltage measuring portion becomes the full-charge voltage again, wherein;

the life-estimation data map is a look-up table associating the voltage difference dV and the temperature of the secondary battery to be measured with the residual life of the secondary battery to be measured and indicating that the wider the voltage difference dV becomes, the shorter the residual life becomes, and the wider the difference between the temperature of the secondary battery to be measured and a predetermined reference temperature, the longer the residual life becomes; and

the CPU allows the voltage measuring portion to measure the terminal voltage V when a preset time elapses for stabilizing the terminal voltage of the secondary battery to be measured since this secondary battery is fully charged and before the secondary battery discharges, and estimates the residual life of the secondary battery to be measured by acquiring the residual life associated with the calculated voltage difference dV and the temperature measured by the temperature measuring portion in the life-estimation data map stored in the second memory.

11. A secondary-battery life estimation method, comprising:

a step of a voltage measuring portion measuring a terminal voltage of a secondary battery to be measured;

a step of a first memory storing in advance a terminal voltage V₀ of a non-degraded secondary battery before the non-degraded secondary battery discharges after fully charged;

a step of a second memory storing in advance a life-estimation data map as a look-up table associating a voltage difference dV between a terminal voltage V of the secondary battery to be measured before the secondary battery to be measured discharges after fully charged and the terminal voltage V₀ with a residual life of the secondary battery to be measured; and

a step of a CPU calculating the voltage difference dV between the terminal voltage V measured by the voltage measuring portion before the secondary battery to be measured discharges after fully charged and the terminal voltage V₀ stored in the first memory and estimating the residual life of the secondary battery to be measured based on the life-estimation data map stored in the second memory using the voltage difference dV.