Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Reexamination Certificate
2000-11-09
2001-10-23
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
C324S426000
Reexamination Certificate
active
06307351
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. HEI 11-318312 filed on Nov. 9, 1999 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a device and a method for determining a state of charge of a battery and, more particularly, to a device and a method for determining a state of charge of a battery based on changing voltage and charging current.
2. Description of the Related Art
An art for determining a state of charge of a battery based on charging voltage and charging current is known.
For example, Japanese Patent Application Laid-Open No. HEI 4-372536 discloses an art in which a battery is charged with (1) a voltage lower than an appropriate charging voltage, (2) the appropriate voltage, and (3) a voltage higher than the appropriate voltage, and a state of charge of the battery is determined by comparing the charging currents corresponding to the charging voltages (1) to (3) with the value of current produced when the battery is normal and in a charge-completed state.
In general, the charging voltage, the charging current, and the state of charge of a battery have a predetermined relationship (charging characteristic). Such a charging characteristic is used by the above-described relevant art to determine a state of charge of a battery. However, as a result of repeated charge/discharge cycles or deterioration over time, the charge characteristic (i.e., the relationship among the charging voltage, the charging current, and the state of charge) changes. Therefore, if a predetermined charging characteristic is used as a basis for determining the state of charge, high-precision determination regarding the state of charge is difficult.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a device capable of always determining a state of charge of a battery with a high precision regardless of repeated charge/discharge cycles and deterioration of the battery over time.
A device for determining state of charge according to one aspect of the invention includes a memory device that stores a relationship among a charging voltage, a charging current and a state of charge of a battery. The device also includes a controller that controls the state of charge, a detector that detects a charging voltage and a charging current at a predetermined state of charge obtained by discharging the battery from a fully charged state. The device also includes a changing device that changes the relationship stored in the memory based on the detected charging voltage and the charging current.
Therefore, high-precision determination regarding the state of charge of a battery is possible, regardless of the state of deterioration of the battery.
REFERENCES:
patent: 5321627 (1994-06-01), Reher
patent: 5411537 (1995-05-01), Munshi et al.
patent: 02-193533 (1990-07-01), None
patent: 04-372536 (1992-12-01), None
patent: 05-134020 (1993-05-01), None
Kenyon & Kenyon
Toyota Jidosha & Kabushiki Kaisha
Tso Edward H.
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