Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Reexamination Certificate
1999-10-06
2001-11-06
Toatley, Jr., Gregory J (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
C320S134000, C320S136000, C320S149000, C320S162000, C324S427000, C324S428000, C324S433000
Reexamination Certificate
active
06313606
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for detecting the capacity of a battery loaded on a piece of electronic equipment, such as a portable personal computer, for furnishing the power. The present invention also relates to an associated battery pack and to an associated electronic equipment system.
2. Description of the Prior Art
In order to know the capacity (residual capacity) of a battery, such as a lithium ion battery, it is generally practiced to estimate the residual capacity from a terminal voltage of the battery or to integrate the efflux current to estimate the residual capacity.
As a method for detecting the capacity (residual capacity) of such battery, there are currently proposed a voltage method and a current integrating method. The voltage method measures the voltage of the battery to calculate the capacity of the battery based on the correlation between the voltage and the capacity of the battery. The current integrating method integrates the current of the battery with respect to time to calculate the capacity of the battery. In the voltage method, the capacity calculation accuracy is high when the current of the battery is small, conversely, in the current integrating method (coulomb method), the capacity calculation accuracy is high when the current of the battery is large. Since the voltage method is based on the voltage, there is no integrating error, but there is a direct error. Since the current integrating method integrates and updates the current with respect to a reference value, the integration error is significant, though the direct error is small.
The voltage method calculates the capacity from the correlation between the capacity and the terminal-to-terminal voltage of the battery (cell voltage). Since the battery (cell) has an internal resistance and a hence A the terminal voltage is fluctuated depending on the flowing current, correction is applied based on the current multiplied by the inner battery voltage. If the current is enlarged, the amount of correction becomes larger to increase the error.
The current integrating method integrates the current with respect to time to find the electrical quantity Ah. For improving the precision, current measurement accuracy needs to be raised. For this reason, an operational amplifier or an analog-to-digital (A/D) converter of extremely high precision is used. Nevertheless, there is produced significant error if charging/discharging is repeated over an extended time interval, or if the current is of a small magnitude, so that contrivances such as calibration are occasionally required such as at the time of charging the battery to its fill capacity. If the calibration timing is lost, significant errors are inevitably produced.
SUMMARY OF THE INVENTION
In view of the above-mentioned problems, an object of the present invention is to provide a battery capacity detection method, a battery pack and an electronic equipment system, in which the voltage method and the current integration method are selectively used depending on the magnitude of the current through the battery to raise the calculation accuracy of the capacity of the battery (residual capacity).
For solving the above problem, the present invention provides a method for detecting the capacity of a battery in which a voltage method of measuring the voltage of the battery to calculate the capacity of the battery, based on the correlation between the voltage and the capacity of the battery, is switched to a current integrating method of integrating the current magnitude of the battery with respect to time, to such is done calculate the capacity of the battery, and vice versa, with a pre-set current magnitude as a threshold value, in order to detect the capacity of the battery.
The present invention also provides a method for detecting the capacity of a battery in which a voltage method of measuring the voltage of the secondary battery, to calculate the capacity of the battery based on the correlation between the voltage and the capacity of the battery, is switched to a current integrating method of integrating the current magnitude of the battery with respect to time to calculate the capacity of the battery, and vice versa, with a pre-set magnitude of voltage drop as a threshold value, in order to detect the capacity of the battery.
With the capacity detection method according to the present invention, the capacity of a battery can be calculated with greater accuracy by switching between the voltage method and the current integrating method responsive to a pre-set current magnitude or to a pre-set magnitude of the voltage drop.
More specifically, the present invention provides a battery pack having the function of detecting the capacity of a battery, wherein the battery pack includes voltage detection means for detecting the voltage of the battery to calculate the capacity of the battery based on; correlation between the voltage and the capacity of the battery, current detection means for detecting the current magnitude of the battery to calculate the capacity of the battery by integrating the current magnitude of the battery with respect to time, and control means for switching between the operation of calculating the capacity of the battery based on the correlation between the voltage and the capacity of the battery responsive to a pre-set current magnitude and the operation of calculating the capacity of the battery by integrating the current magnitude of the battery with respect to time.
With the pack of the battery according to the present invention, the control means is responsive to the pre-set current magnitude or to the pre-set magnitude of the voltage drop to switch between the operation of calculating the capacity of the battery based on the correlation between the voltage and the capacity of the battery and the operation of calculating the capacity of the battery by integrating the current magnitude of the secondary battery with respect to time to improve the accuracy in capacity calculations.
The electronic equipment system of the present invention resides in the above-described battery pack loaded on a piece of electronic equipment, such as a personal computer, in which the calculation accuracy of the battery can be improved by switching between the voltage method and the current integrating method during the capacity calculations.
Additional features and advantages of the present invention are described in, and will be apparent from, the Detailed Description of the Preferred Embodiments and the Description of the Drawings.
REFERENCES:
patent: 5140251 (1992-08-01), Wu
patent: 5596260 (1997-01-01), Moravec et al.
patent: 5-134020 (1993-05-01), None
patent: 8-163705 (1996-06-01), None
Sonnenschein Nath & Rosenthal
Sony Corporation
Toatley Jr. Gregory J
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