Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Reexamination Certificate
2003-09-09
2004-12-07
Tibbits, Pia (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
C320S155000
Reexamination Certificate
active
06828761
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a charging/discharging apparatus, and particularly to a battery charging/discharging apparatus and a battery charging/discharging method in which the remaining capacity of a battery can be determined with high accuracy.
2. Description of the Related Art
FIG. 1
is a block diagram showing an example structure of a conventional battery pack
1
.
The battery pack
1
includes cells
12
-
1
and
12
-
2
connected in series (hereinafter collectively referred to as “battery
12
”, unless the cells
12
-
1
and
12
-
2
should be discriminated), which may comprise lithium ion batteries, for powering electronic devices. The positive electrode of the cell
12
-
1
is connected to a battery terminal
11
-
1
while the negative electrode of the cell
12
-
2
is connected to a battery terminal
11
-
2
via a resistor
13
provided for current detection and a protection device
14
. When the battery pack
1
is attached to an electronic device (not shown), the battery terminals
11
-
1
and
11
-
2
are connected to connection terminals of the electronic device so that the electronic device can be powered by the battery
12
.
A cell voltage detector
15
detects a cell voltage when the cell
12
-
1
and the cell
12
-
2
are connected in series, and outputs the detection result to a microcomputer
17
. A charging/discharging current detector
16
detects the direction and value of voltage drop due to the current flowing to the resistor
13
in order to detect the existence of a charging current or a discharging current. The result is then output to the microcomputer
17
. The protection device
14
protects the battery
12
from being overcharged or overdischarged.
The microcomputer
17
calculates the remaining battery capacity value based on the cell voltage supplied from the cell voltage detector
15
, and stores the resulting value in an internal memory
17
a
. The microcomputer
17
switches to wake-up mode if a charging current or a discharging current is supplied from the charging/discharging current detector
16
or if it receives incoming data from the outside. If no charging/discharging current is supplied within a predetermined time or if no incoming data is received while it is in wake-up mode, the microcomputer
17
switches to sleep mode.
FIG. 2
is a flowchart of the process for calculating the remaining battery capacity value of the battery pack
1
shown in FIG.
1
.
At step S
1
, the microcomputer
17
determines whether or not the battery
12
has been charged, i.e., whether or not a charging current has been supplied from the charging/discharging current detector
16
. If it is determined at step S
1
that the battery
12
has been charged, the process proceeds to step S
2
, in which the additional capacity value is calculated by equation (1) as follows;
additional capacity value=charging current value×sampling interval (1)
After the additional capacity value has been calculated at step S
2
, at step S
3
the microcomputer
17
reads the remaining capacity value stored in the memory
17
a
, and calculates the up-to-date remaining capacity value by equation (2) as follows:
up-to-date remaining capacity value=remaining capacity value read from the memory
17
a
+additional capacity value (2)
At step S
3
, the microcomputer
17
stores the up-to-date remaining capacity value calculated by equation (2) in the memory
17
a
or updates the existing remaining capacity value, and the process returns to step S
1
to iterate the above-described operation.
If it is determined at step S
1
that the battery
12
has not been charged, the process proceeds to step S
4
, in which the microcomputer
17
further determines whether or not the battery
12
has been discharged, i.e., whether or not a discharging current has been supplied from the charging/discharging current detector
16
. If it is determined at step S
4
that it has not been discharged, the process returns to step S
1
to iterate the above-described operation.
If it is determined at step S
4
that the battery
12
has been discharged, the process proceeds to step S
5
, in which the microcomputer
17
calculates the reduced capacity value by equation (3) as follows:
reduced capacity value=discharging current value×sampling interval (3)
After the reduced capacity value has been calculated at step S
5
, at step S
6
, the microcomputer
17
reads the remaining capacity value stored in the memory
17
a
, and calculates the up-to-date remaining capacity value by equation (4) as follows:
up-to-date remaining capacity value=remaining capacity value read from the memory
17
a
−reduced capacity value (4)
At step S
6
, the microcomputer
17
stores the up-to-date remaining capacity value calculated by equation (4) in the memory
17
a
or updates the existing remaining capacity value, and the process returns to step S
1
to iterate the above-described operation.
Accordingly, the calculation process using a charging current or a discharging current is performed to determine the remaining battery capacity.
The microcomputer
17
utilizes the power supplied from the battery
12
in order to determine the remaining battery capacity. Hence, when the battery is in standby mode (when the remaining battery capacity calculation process is not performed), the microcomputer
17
switches to sleep mode in order to reduce the power consumption of the microcomputer
17
. This may suppress discharge current (leakage current) of the battery
12
in standby mode.
When the charging/discharging current detector
16
detects a charging current or a discharging current, the microcomputer
17
switches to wake-up mode; however, discharge current (leakage current) when the battery is in standby mode is minute, and thus cannot be detected by the charging/discharging current detector
16
.
As a result, when the battery pack
1
is in standby mode, a trace amount of discharge current (leakage current) flows, but the accumulated current (standby current×standby time) cannot be measured or detected because the microcomputer
17
is in sleep mode. Therefore, if the battery pack
1
is in standby mode for a long time, there is a problem in that the remaining capacity value stored in the memory
17
a
by the microcomputer
17
might be relatively greater than the actual remaining capacity value (actual capacity value).
If the microcomputer
17
is forced not to enter sleep mode and is allowed to detect the standby current, the current will be minute, and will not be able to be precisely detected. There still exists such a problem that an error occurs between the remaining capacity value stored in the memory
17
a
and the actual capacity value.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a battery charging/discharging apparatus and a battery charging/discharging method in which the remaining battery capacity can be determined with high accuracy.
To this end, in one aspect of the present invention, a battery charging/discharging apparatus for determining the remaining capacity of a battery includes a measuring unit for measuring a standby time of the battery, a correction value calculating unit for calculating a correction value for the remaining capacity of the battery based on the standby time measured by the measuring unit, and a correcting unit for correcting a current remaining capacity value of the battery based on the correction value calculated by the correction value calculating unit.
The battery charging/discharging apparatus may further include a determining unit for determining whether or not the standby time has reached a predetermined time. The correction value calculating unit may calculate the correction value for the remaining capacity of the battery at a predetermined time interval based on the result of the determining unit.
According to the present invention, a battery charging/discharging method for d
Sato Hideyuki
Suzuki Mamoru
Maioli Jay H.
Sony Corporation
Tibbits Pia
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