Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Reexamination Certificate
2000-07-05
2001-04-24
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
C320S162000
Reexamination Certificate
active
06222345
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to a control device for a battery, which is charged by an electric power supplied through a power supplying line for charging the battery.
(2) Description of the Related Art
A battery loaded on a hybrid or electric vehicle for supplying power to a motor for traveling is charged as the need arises by reverse electromotive force arising in the motor upon speed reducing of the vehicle or an electric power from an alternator drived by an engine.
It is well known that a full charging capacity of a battery changes depending on change in surrounding temperature. If the change in the full charging capacity is not followed correctly, a charge of battery is controlled on the basis of a constant full charging capacity in spite of temperature change, resulting in an overcharging of the battery and deterioration in a charging performance of the battery.
A measure to solve the above problem may be as follows: a charging current flowing in a power supplying line for charging the battery and a terminal voltage of the battery are measured; a correlation between the charging current and the terminal voltage is computed; and a full charging capacity of the battery is evaluated on the basis of the correlation.
A change in an internal impedance of the battery when the battery approachs its fully charged state varies depending upon surrounding temperature. Therefore, when the battery is controlled on the basis of the full charging capacity simply derived from the correlation between the charging current and the terminal voltage without taking a factor of temperature into consideration, the battery might not be controlled properly since the full charging capacity derived in such a manner is not accurate.
The problem in controlling a battery described above widely arises for general batteries subjected to repeated charge and discharge besides the battery loaded on a hybrid or electric vehicle.
SUMMARY OF THE INVENTION
It is therefore an objective of the present invention to solve the above problem and to provide a device capable to accurately controll a battery, which is charged by an electric power supplied through a power supplying line for charging.
In order to attain the above objective, as shown in
FIG. 1
illustrating a basic construction of a control device for a battery according to the present invention, the present invention is to provide a device for controlling a battery
1
charged by an electric power supplied through a power supplying line
15
for charging, comprising: voltage measuring means Vm for measuring a terminal voltage of the battery
1
; current measuring means Im for measuring a charging current flowing through the power supplying line
15
for charging; charging characteristic computing means
21
A for computing an approximate correlated linear characteristic between the terminal voltage and the charging current on the basis of periodic changes in the terminal voltage measured by the voltage measuring means Vm and in the charging current measured by the current measuring means Im during a charging operation of the battery
1
; and full charging capacity computing means
21
B for computing a full charging capacity of the battery
1
on the basis of the approximate correlated linear characteristic computed by the charging characteristic computing means
21
A and a predetermined reference value of the charging current.
With the construction of the control device for a battery described above, the full charging capacity computing means
21
B computes the full charging capacity of the battery
1
on the basis of an approximate correlated linear characteristic computed by the charging characteristic computing means
21
A between the terminal voltage and the charging current of the battery
1
, together with not an actual charging current measured by the current measuring means Im flowing through the power supplying line
15
for charging, but a predetermined reference value of the charging current. Therefore, even if the charging current in a state in the vicinity of the fully charged state of the battery significantly changes in response to surrounding temperature caused by a fluctuation of change in an internal impedance of the battery due to the surrounding temperature, the full charging capacity of the battery
1
can be accurately computed on the basis of the approximate correlated linear characteristic between the terminal voltage and the charging current of the battery
1
.
The predetermined reference value of the charging current is a value showing a linear changing characteristic with respect to a change in the charging capacity of the battery
1
.
With the construction described above, the full charging capacity computing means
21
B accurately computes a full charging capacity of the battery
1
at any time from the beginning to the end of a charging operation.
The control device for a battery
1
further comprises charging end control means
21
C for controlling an end of charging operation of the battery
1
in response to the full charging capacity thereof, wherein the charging characteristic computing means
21
A computes the approximate linear characteristic whenever the charging operation of the battery
1
arises, the full charging capacity computing means
21
B computes the full charging capacity of the battery
1
whenever the charging operation of the battery
1
arises, and the charging end control means
21
C changes a timing of an end of charging operation of the battery
1
in response to the full charging capacity thereof most currently computed whenever the full charging capacity computing means
21
B computes the full charging capacity of the battery
1
.
With the construction described above, since the charging end control means
21
C changes a timing of an end of charging operation of the battery
1
in response to the most current value of the full charging capacity among values thereof computed by the full charging capacity computing means
21
B whenever the charging operation of the battery
1
arises, the end of charging operation of the battery
1
is controlled by the charging end control means
21
C in response to the full charging capacity computed by the full charging capacity computing means
21
B during the charging operation.
REFERENCES:
patent: 5936383 (1999-08-01), Ng et al.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Tso Edward H.
Yazaki -Corporation
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