Electricity: measuring and testing – Electrolyte properties – Using a battery testing device
Reexamination Certificate
2002-04-29
2003-02-18
Toatley, Jr., Gregory J. (Department: 2838)
Electricity: measuring and testing
Electrolyte properties
Using a battery testing device
Reexamination Certificate
active
06522148
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for measuring a state of charge of, for example, a battery device and particularly relates to a technique for correcting the state of charge of the battery obtained by calculation based on integrated electric current.
2. Description of the Related Art
When measuring a state of charge (SOC) of a battery, provided, for example, in a hybrid vehicle, the following method is known as a typical method, in which, since the state of charge is proportional to the total amount of charge stored in the battery, a total amount of charge and a total amount of discharge are first calculated by integrating a charge current and a discharge current detected for each predetermined period of time, and the state of charge of the battery can then be obtained by addition or subtraction of the integrated quantity of charge and the integrated quantity of discharge to or from an initial state of the battery or the initial state of charge of the battery immediately before starting charge and discharge.
However, the above method has a drawback in that, when obtaining the state of charge by measuring the integrated quantity of charge and the integrated quantity of discharge, the error contained in the calculated state of charge of the battery increases because errors in measurements of the charge current or the discharge current by the current detector in every current measurement is integrated.
In order to obtain an accurate value of the state of charge by the above total current integration method, Japanese Unexamined Patent Application, First Publication No. Hei 6-6901 proposes a battery state of charge measuring apparatus. The proposed detecting device first calculates an electrical consumption after correcting a standard consumption obtained by integrating the discharge current of the battery by multiplying each correction coefficient in response to battery terminal voltage, density, temperature, and discharge current, and the state of charge is calculated by obtaining a difference value obtained by subtracting the above electrical consumption from the initial charge of the battery and then by correcting the difference value by multiplying respective correction coefficients regarding a quantity of charge, a quantity of discharge before charging, the number of times of charging, a temperature at charging, and so on.
In the aforementioned state of charge measuring apparatus according to one example of the conventional techniques, various correction coefficients are employed obtained by previously stored predetermined relational equations or maps. Since these relational equations and maps are prepared according to characteristic properties at a predetermined state of the battery, for example, stable properties at a stationary state of the battery, a problem arises that the estimated state of charge of the battery obtained by the predetermined relational equations or maps may be separated from an actual value, when a storage capacity of the battery has been changed due to long term use or when the battery is replaced with a different type battery.
As described above, when the state of charge of the battery contains an error, there is a possibility to set a state of charge which differs from the controllable range of the battery, which may results in shortening of the service life of the battery or result in causing defective control of the motor or the engine.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems and an object of the present invention is to provide a battery state of charge measuring apparatus, capable of obtaining an accurate state of charge of a battery based on a value obtained by integrating charge and discharge currents, even when the battery properties have been changed after a long-term use or even when the battery has been replaced.
The first aspect of the present invention provides a state of charge measuring apparatus for a battery device comprising a battery (for example, a battery
14
in the embodiment shown below), a load (for example, a motor M in the embodiment shown below) driven by electrical power supplied from the battery device, and a state of charge calculating device (for example, integrated state of charge calculating portion
32
in the embodiment shown below) for detecting a charge and discharge currents (for example, charge and discharge currents I in the embodiment shown below) of the battery device and for calculating an integrated state of charge of the battery device (for example, integrated SOC in the embodiment shown below) based on an integrated value (for example, a consumed charge Q in the embodiment shown below) of charge and discharge currents, comprising a voltage detecting device (for example, a voltage detector
16
in the embodiment shown below) for detecting a terminal voltage (for example, a terminal voltage V in the embodiment shown below) of the battery, an upper limit substitution device (for example, an upper and lower limit substitution device
33
in the embodiment shown below) for substituting the integrated state of charge value to an upper limit state of charge (for example, an upper limit SOC in the embodiment shown below) when a detected voltage obtained by the terminal voltage detecting device exceeds a predetermined voltage (for example, an upper limit voltage VU in the embodiment shown below), and a decreasing side corrected state of charge calculating device (for example, corrected state of charge calculating portion
35
in the embodiment shown below) for calculating a corrected state of charge (for example, corrected SOC in the embodiment shown below) by correcting the integrated state of charge after the data substitution when the state of charge of the battery is decreasing, wherein the decreasing side corrected state of charge calculating device (for example, the corrected state of charge calculating portion
35
in the embodiment shown below) corrects such that a difference between the integrated state of charge and the corrected state of charge increases as the integrated value of the charge and discharge currents increases.
By constructing the state of charge measuring apparatus as shown above, the integrated state of charge data can be substituted to a predetermined upper limit in response to the terminal voltage, and a correction processing is carried out such that a difference between the integrated state of charge obtained after the data substitution and the corrected state of charge after correcting the integrated state of charge increases with the integrated value of the charge and discharge currents.
Even when a difference between the integrated state of charge and the actual state of charge increases as the integrated value of the charge and discharge currents increases, it is possible to improve the accuracy for approximating the corrected state of charge to the actual state of charge.
According to the second aspect, the state of charge measuring apparatus for a battery device comprising a battery device (for example, a battery
13
in the embodiment shown below), a load (for example, a motor M in the embodiment shown below) driven by electrical power supplied from the battery device and a state of charge calculating device (for example, an integrated state of charge calculating device
32
in the embodiment shown below) for detecting a charge current and discharge currents (for example, charge and discharge currents I in the embodiment shown below) of the battery device and for calculating an integrated state of charge of the battery based on an integrated value (for example, a consumed charge Q in the embodiment shown below) of the charge and discharge currents, comprising, a voltage detecting device (for example, a voltage detector
16
in the embodiment shown below) for detecting a terminal voltage (for example, a terminal voltage V in the embodiment shown below) of the battery device, an lower limit substitution device (for example, a upper and lower limit values subst
Ochiai Shinobu
Ohnuki Yasumichi
Shibutani Atsushi
Arent Fox Kintner & Plotkin & Kahn, PLLC
Honda Giken Kogyo Kabushiki Kaisha
Toatley , Jr. Gregory J.
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