BATTERY CONTROL DEVICE, POWER STORAGE DEVICE, POWER STORAGE
METHOD, AND PROGRAM
5
TECHNICAL FIELD
[0001]
The present invention relates to a battery control
device that controls a secondary battery, a power storage
10 device, a power storage method, and a program.
BACKGROUND ART
[0002]
Recently, a secondary battery such as a lithium ion
battery has been used in various fields so as to reduce
15 environmental load. Deterioration of the secondary battery
progresses while in use. To reduce the running cost of the
secondary battery, it is necessary to suppress the progress
of the deterioration.
[0003]
20 Patent Document 1 and Patent Document 2 disclose a
method of stably supplying electric energy for a long period
of time by alternately charging and discharging two or more
sets of secondary batteries so as to increase operational
lifetime of the secondary batteries.
25 RELATED DOCUMENT
PATENT DOCUMENT
[0004]
[Patent Document 1] Japanese Unexamined Patent
Publication No. 59-206680
[Patent Document 2] Japanese Unexamined Patent
Publication No. 02-270270
5
DISCLOSURE OF THE INVENTION
[0005]
However, a discharging amount of the secondary battery
on a discharging side may vary in accordance with an amount
10 of electric power desired on a user side. In addition, if
a state in which the amount of electric power desired on the
user side is large continues, in a technology of the
above-described patent documents, in a state in which
charging of a secondary battery on a charging side is not
15 sufficient, a secondary battery on a discharging side is apt
to be discharged up to a battery capacity at which the
charging side and the discharging side are switched, and thus
there is a concern that an amount of electric power desired
by the user may not be secured.
20 [0006]
An object of the invention is to provide a battery
control device, a power storage device, a power storage
method, and a program which are capable of securing an amount
of electric power of a secondary battery in a relatively
25 stable manner.
[0007]
According to an aspect of the invention, there is
3
provided a battery control device including: a measurement
unit that individually measures an amount of discharging
current of a discharging secondary battery among a plurality
of secondary batteries which are independently charged and
5 discharged; a time calculating unit that calculates time
required until the secondary battery has a constant battery
capacity for each of the discharging secondary batteries on
the basis of a discharging current rate for each of the
secondary batteries which is calculated on the basis of the
10 amount of discharging current, and a state of charge (SOC)
of the secondary battery; a number calculating unit that
calculates an expected number of the secondary batteries,
which become fully charged in the required time, on the basis
of a charging current rate for each of the secondary batteries
15 which is calculated on the basis of an amount of charging
current of the charging secondary battery, the SOC of the
secondary battery, and the required time, and calculates a
total value of the expected number and the existing number
of secondary batteries which are already fully charged; and
20 a control unit that determines whether or not to raise the
charging current rate on the basis of the total value.
[0008]
According to another aspect of the invention, there is
provided a power storage device including: a plurality of
25 secondary batteries which are independently charged and
discharged; a measurement unit that individually measures
an amount of discharging current of each of the discharging
secondary batteries; a time calculating unit that calculates
time reguired until the secondary battery has a constant
battery capacity for each of the discharging secondary
batteries on the basis of a discharging current rate for each
5 of the secondary batteries which is calculated on the basis
of the amount of discharging current, and a state of charge
(SOC) of the secondary battery; a number calculating unit
that calculates an expected number of the secondary batteries,
which become fully charged in the required time, on the basis
10 of a charging current rate for each of the secondary batteries
which is calculated on the basis of an amount of charging
current of the charging secondary battery, the SOC of the
secondary battery, and the required time, and calculates a
total value of the expected number and the existing number
15 of secondary batteries which are already fully charged; and
a control unit that determines whether or not to raise the
charging current rate on the basis of the total value.
[0009]
According to still another aspect of the invention,
20 there is provided a power storage method including allowing
a computer to: individually measure an amount of discharging
current of a discharging secondary battery among a plurality
of secondary batteries which are independently charged and
discharged; calculate time required until the secondary
25 battery has a constant battery capacity for each of the
discharging secondary batteries on the basis of a discharging
current rate for each of the secondary batteries which is
5
calculated on the basis of the amount of discharging current,
and a state of charge (SOC) of the secondary battery;
calculate an expected number of the secondary batteries,
which become fully charged in the required time, on the basis
5 of a charging current rate for each of the secondary batteries
v/hich is calculated on the basis of an amount of charging
current of the charging secondary battery, the SOC of the
secondary battery, and the required time, and calculate a
total value of the expected number and the existing number
10 of secondary batteries which are already fully charged; and
determine whether or not to raise the charging current rate
on the basis of the total value.
[0010]
According to still another aspect of the invention,
15 there is provided a program that allows a computer function
as: a measurement unit that individually measures an amount
of discharging current of a discharging secondary battery
among a plurality of secondary batteries which are
independently charged and discharged; a time calculating
20 unit that calculates time required until the secondary
battery has a constant battery capacity for each of the
discharging secondary batteries on the basis of a discharging
current rate for each of the secondary batteries which is
calculated on the basis of the amount of discharging current,
25 and a state of charge (SOC) of the secondary battery; a number
calculating unit that calculates an expected number of the
secondary batteries, which become fully charged in the
6
required time, on the basis of a charging current rate for
each of the secondary batteries which is calculated on the
basis of an amount of charging current of the charging
secondary battery, the SOC of the secondary battery, and the
5 required time, and calculates a total value of the expected
number and the existing number of secondary batteries which
are already fully charged; and a control unit that determines
whether or not to raise the charging current rate on the basis
of the total value.
10 [0011]
According to the invention, it is possible to secure
an amount of electric power of a secondary battery in a
relatively stable manner.
BRIEF DESCRIPTION OF THE DRAWINGS
15 [0012]
The above and other objects, advantages and features
of the present invention will be more apparent from the
following description of certain preferred exemplary
embodiments taken in conjunction with the accompanying
20 drawings.
[0013]
FIG. 1 is a view illustrating a configuration example
of a battery control device according to a first exemplary
embodiment.
25 FIG. 2 is a view illustrating a configuration example
of a power storage device according to the first exemplary
embodiment.
7
FIG. 3 is a flowchart illustrating a process flow of
the battery control device according to the first exemplary
embodiment.
FIG. 4 is a view illustrating a flow of raising a
5 charging current rate by the battery control device.
FIG. 5 is a flowchart illustrating a"process flow of
a battery control device according to a second exemplary
embodiment.
FIG. 6 Is a view illustrating a flow of lowering a
10 charging current rate by the battery control device.
FIG. 7 is a view illustrating a configuration example
of a battery control device according to a third exemplary
embodiment.
FIG. 8 is a view illustrating an example of information
15 that is stored in an SOH storage unit.
FIG, 9 is a flowchart illustrating a process flow of
the battery control device according to the third exemplary
embodiment.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
20 [0014]
Hereinafter, exemplary embodiments of the invention
will be described with reference to the accompanying drawings .
In all drawings, like reference numerals will be given to
like constituent elements having substantially the same
25 functions, and description thereof will not be repeated.
[0015]
In addition, in the following description, respective
8
processing units of a battery control device 100 indicate
a block in a function unit instead of a configuration in a
hardware unit. The respective processing units of the
battery control device 100 are realized by a CPU, a memory,
5 a program loaded to the memory to realize component elements
of the accompanying drawings, a storage medium such as a hard
disk that stores the program, and an arbitrary combination
of hardware and software with a focus on a network connection
interface in an arbitrary computer. In addition, a method
10 and a device for realization thereof include various
modification examples.
[0016]
(First Exemplary Embodiment)
FIG. 1 is a view illustrating a configuration example
15 of the battery control device 100 according to a first
exemplary embodiment. The battery control device 100
includes a measurement unit 110, a time calculating unit 120,
a number calculating unit 130, and a control unit 140.
[0017]
20 The measurement unit 110 is connected to a plurality
of secondary batteries (not illustrated), and individually
measures an amount of discharging current of a discharging
secondary battery among the plurality of secondary batteries.
In addition, measurement unit 110 further measures an amount
25 of charging current, a voltage value, and the like of a
charging secondary battery. In this exemplary embodiment,
the measurement unit 110 includes a determination unit {not
9
illustrated) that determines whether or not the secondary
battery becomes fully charged by using a measured voltage
value and the like. In addition, the determination unit
stores the number (existing number) of the secondary
5 batteries which are determined as the fully charged state
in an existing number storage unit (not illustrated) such
as a memory and a hard disk.
[0018]
The time calculating unit 120 calculates time required
10 until the discharging secondary battery reaches a constant
battery capacity. Specifically, the time calculating unit
120 calculates a discharging current rate of the secondary
battery on the basis of the amount of discharging current
of the discharging secondary battery which is measured by
15 the measurement unit 110. Here, the discharging current
rate is expressed with a unit "C". In addition, a
discharging current rate of "1 C" represents a state in which
a discharging current flows at a rate at which a secondary
battery in a fully charged state is completely discharged
20 in one hour. In addition, the time calculating unit 12 0
calculates time required until the secondary battery reaches
a constant battery capacity for each of the discharging
secondary batteries on the basis of the discharging current
rate that is calculated, and a state of charge (SOC) of the
25 secondary battery. Here, for example, the "constant battery
capacity" may be set to a battery capacity of 0% (completely
discharged state) or a battery capacity of 10% or 20% with
10
a margin to some extent, or may be set by a user in an arbitrary
manner in accordance with a use and the like.
[0019]
The number calculating unit 130 calculates a total value
5 of an expected number of the secondary batteries which become
fully charged in the required time calculated by the time
calculating unit 120, and the number of secondary batteries
which are already fully charged. Specifically, the number
calculating unit 130 calculates the charging current rate
10 of the secondary battery on the basis of the amount of
charging current of the charging secondary battery. Here,
the charging current rate is expressed by the unit "C" similar
to the discharging current rate. Here, a charging current
rate of "1 C" represents a state in which a charging current
15 flows at a rate at which a secondary battery in a fully
discharged state is completely charged in one hour. In
addition, the number calculating unit 130 calculates the
number of secondary batteries (expected number), which
become fully charged in the required time, on the basis of
20 the charging current rate that is calculated, the SOC of each
of the secondary batteries, and the required time that is
calculated for each of the discharging secondary batteries.
Here, for example, the number calculating unit 130 calculates
the expected number of the secondary batteries which become
25 fully charged on the basis of the shortest required time among
required times of the discharged secondary batteries which
are calculated by the time calculating unit 120. In addition,
11
the number calculating unit 130 calculates a total value of
the expected number that is calculated, and the existing
number that is stored in the existing number storage unit.
[0020]
5 The control unit 140 determines whether or not to raise
the amount of charging current of the charging secondary
batteries on the basis of the total value that is calculated
by the number calculating unit 130. Specifically, the
control unit 140 determines whether or not the total value
10 calculated by the number calculating unit satisfies the
number of secondary batteries necessary for preparation of
a desired amount of electric power. In addition, in a case
where it is determined that the number of secondary batteries
necessary for preparation of the desired amount of electric
15 power is not satisfied, the control unit 140 raises the
charging current rate of the charging secondary batteries.
In addition, the control unit 140 connects the plurality of
secondary batteries to an external power supply (for example,
a centralized power supply) and a load. In addition, for
20 example, the control unit 140 includes an alternating current
(AC)-direct current (DC) converting unit (not illustrated).
For example, during charging of the secondary batteries, the
control unit 140 converts power from the centralized power
supply to DC power by using the AC-DC converting unit. In
25 addition, during discharging of the secondary batteries, the
control unit 140 converts power from the secondary batteries
to AC power by using the AC-DC converting unit.
12
[0021]
FIG. 2 is a view illustrating a configuration example
of a power storage device 10 according to the first exemplary
embodiment. The power storage device 10 includes the
5 battery control device 100 and a battery section 200. In
FIG. 2, the battery control device 100 further includes an
existing number storage unit 150. In addition, the existing
number storage unit 150 may be provided to other devices which
are located at the outside of the battery control device 100.
10 The battery section 200 includes a plurality of secondary
batteries 210. The plurality of secondary batteries 210 can
be independently charged and discharged under the control
of the control unit 140. Here, for example, the secondary
batteries 210 are lithium ion secondary batteries. The
15 secondary batteries 210 may be obtained by connecting a
plurality of secondary battery packages in series. Each of
the second battery packages may be obtained by connecting
a plurality of secondary battery cells in parallel.
[0022]
20 A process flow of the battery control device 100
according to this exemplary embodiment will be described with
reference to FIG. 3. FIG. 3 is a flowchart illustrating a
process flow of the battery control device 100 according to
the first exemplary embodiment.
25 [0023]
The battery control device 100 selects an arbitrary
secondary battery 210 that is a target among a plurality of
13
secondary batteries which are in a connected state, and
determines whether or not the secondary battery 210 is in
a fully charged state (S102). In a case where the secondary
battery 210 that is a target is in the fully charged state
5 (YES in S102), the battery control device 100 increments an
existing number of the secondary batteries 210 in the fully
charged state (S104), and stores the existing number in the
existing number storage unit 150. On the other hand, in a
case where the state of the secondary battery 210 that is
10 the target is not in the fully charged state (NO in S102),
the battery control device 100 determines whether the
secondary battery 210 is in a state of discharging or charging
(S106).
[0024]
15 In a case where the secondary battery 210 that is a
target is discharging (discharging in S106), the battery
control device 100 measures an amount of discharging current
of the secondary battery 210 (S108) . In addition, the
battery control device 100 calculates a discharging current
20 rate of the secondary battery 210 on the basis of the amount
of discharging current that is measured in S108, and a fully
charged battery capacity (S110). For example, the
discharging current rate can be calculated by using the
following Equation 1.
25 [Ma t hema t i ca1 Fo rmula 1]
14
r „ n AMOUNT OF DISCHARGING CURRENT [A]
DISCHARGING CURRENT RATE [C] =
FULLY CHARGED BATTERY CAPACITY [Ah]
• • - (EQUATION 1)
[ 0 0 2 5 ]
In a d d i t i o n , the b a t t e r y c o n t r o l device 100 c a l c u l a t es
an SOC of the secondary b a t t e r y 210 on the b a s i s of a c u r r e nt
5 b a t t e r y c a p a c i t y of the discharging secondary b a t t e r y 210
and a f u l l y charged b a t t e r y capacity thereof (S112). For
example, the SOC can be c a l c u l a t e d by using the following
Equation 2 .
[Mathematical Formula 2]
„ r , CURRENT BATTERY CAPACITY [Ah]
SOC[%] = Z x l O O • • .(EQUATION2)
FULLY CHARGED BATTERY CAPACITY [Ah]
10
[0026]
In addition, the battery control device 100 calculates
time required until the secondary battery 210 reaches a
constant battery capacity on the basis of the discharging
15 current rate that is calculated in S110, and the SOC of the
discharging secondary battery 210 which is calculated in S112
(S114). For example, the required time can be calculated
by using the following Equation 3. The battery control
device 100 temporarily stores the required time, which is
20 calculated, in a storage region of a memory and the like.
[Mathematical Formula 3]
15
REQUIRED TIME T/il = S0C 0F DISCHARGING SECONDARY BATTERY[%]
DISCHARGING CURRENT RATE [C]
• • • (EQUATION 3)
[0027]
On the other hand, in a case where the secondary battery
210 that is a target is charging (charging in S106), the
5 battery control device 100 acquires an amount of charging
current of the secondary battery 210 (S116). Here, as the
amount of charging current, a predetermined amount of current
based on product specifications of the secondary battery 210
may be stored in advance in the storage region of the memory
10 and the like and the stored value may be used, or an actual
measurement value that is measured by the measurement unit
110 and the like may be used. In addition, it is preferable
to use the value that is measured by the measurement unit
110 and the like when considering calculation of a charging
15 completion time with accuracy. In addition, the battery
control device 100 calculates a charging current rate of the
secondary battery 210 on the basis of the amount of charging
current that is acquired in S116 (S118) . For example, the
charging current rate can be calculated by using the
20 following Equation 4.
[Mathematical Formula 4]
r , AMOUNT OF CHARGING CURRENT [A]
CHARGING CURRENT RATE [C] = LT 7 -I FULLY CHARGED BATTERY CAPACITY [Ah]
• • • (EQUATION 4)
[0028]
16
In addition, as is the case with the discharging
secondary battery 210, the battery control device 100
calculates an SOC of the charging secondary battery 210
(S120). The battery control device 100 temporarily stores
5 the SOC, which is calculated, in the storage region of the
memory and the like.
[0029]
In addition, the battery control device 100 determines
whether or not the state of all secondary batteries 210 is
10 confirmed (S122) . In a case where the confirmation of the
state with respect to all of the secondary batteries 210 is
not completed {NO in S122), the above-described processes
(S102 to S120) are repeated so as to confirm the state of
a secondary battery 210 that is not confirmed yet. On the
15 other hand, in a case where the state of all of the secondary
batteries 210 is confirmed (YES in S122) , the battery control
device 100 transitions the subsequent process (S124).
[0030]
The battery control device 100 calculates an expected
20 number of the secondary batteries 210 of which charging is
completed in the required time on the basis of the required
time that is calculated in S114, the charging current rate
that is calculated in S118, and the SOC that is calculated
in S120 (S124) . For example, in a predetermined secondary
25 battery 210 being charged, in a case where the charging
current rate is 1 C, and the SOC is 50%, the battery control
device 100 can calculate that 0.5 h are taken until charging
17
of the secondary battery 210 is completed. In addition, the
battery control device 100 determines whether or not charging
of the secondary battery 210 is completed in the required
time in accordance with whether or not the required time is
5 equal to or greater than 0.5 h to calculate the expected
number. In addition, a method of calculating the expected
number is not limited thereto. For example, the expected
number can be calculated by a method in which a battery
capacity chargeable in the required time is calculated on
10 the basis of the charging current rate of the predetermined
secondary battery 210 and the required time, and
determination of whether or not the calculated battery
capacity is deficient for setting of the SOC of the secondary
battery 210 to 100% is performed. Here, when calculating
15 the expected number, the battery control device 100 may use
the shortest required time among respective required times
calculated in S114, or may use a required time taken until
the secondary batteries 210 in a number exceeding a
predetermined threshold value reach a constant battery
20 capacity. Here, description will be made with respect to
a case where the battery control device 100 uses the shortest
required time as an example.
[0031]
In addition, the battery control device 100 determines
25 whether or not the total value of the expected number that
is calculated in S124 and the existing number that is stored
in the existing number storage unit 150 in S104 is equal to
18
or greater than a predetermined number (S126). Here, for
example, the predetermined number is the number of the
secondary batteries 210 with which a desired amount of
electric power, which is set in advance by a user on the basis
5 of demand forecasting and the like, can be secured.
According to this, the predetermined number is appropriately
changed in accordance with an installation environment, a
use, and the like of the power storage device 10. In a case
where the total value is less than a predetermined number
10 {NO in S126), the battery control device 100 determines that
it is difficult to prepare a necessary number of secondary
batteries 210 in the fully charged state after passage of
the required time, and thus it is difficult to secure the
desired amount of electric power. In this case, the battery
15 control device 100 performs control so as to prepare the
necessary number of secondary batteries 210 in the fully
charged state by raising the charging current rate (S128) .
[0032]
Here, in a case of raising the charging current rate,
20 the battery control device 100 may raise the charging current
rate of all of the charging secondary batteries 210, or may
raise the charging current rate of parts of the secondary
batteries 210. In a case of raising the charging current
rate of parts of the secondary batteries 210, it is preferable
25 that the battery control device 100 performs sequential
selection from a secondary battery 210 that is the closest
to the fully charged state among the charging secondary
19
batteries 210 which do not become fully charged in the
required time as a target of which the charging current rate
is to be raised. According to this manner, it is possible
to reduce an increment width of the charging current rate
5 of the selected secondary battery 210, and thus it is possible
to suppress deterioration of the secondary battery 210 while
securing a desired amount of electric power. In addition,
the battery control device 100 calculates the number of the
secondary batteries 210 of which the charging current rate
10 is to be raised from a difference between the predetermined
number, and the total value of the expected number and the
existing number which is to be calculated in S126. For
example, in a case where the predetermined number is 5, and
the total value that is calculated in S126 is 3, the battery
15 control device 100 can calculate that the number of the
secondary batteries 210 of which the charging current rate
is to be raised is "5-3 = 2". In this case, among the charging
secondary batteries 210 which do not become fully charged
in the required time, the battery control device 100 selects
20 a secondary battery 210 that is the closest to the fully
charged state and a secondary battery 210 that is second
closest to the fully charged state as a target of which the
charging current rate is to be raised.
[0033]
25 In addition, for each of the selected secondary
batteries 210, the battery control device 100 calculates an
amount of charging current that becomes a charging current
20
rate, with which charging of the secondary battery 210 is
completed in the required time, on the basis of a remaining
battery capacity until the secondary battery 210 becomes
fully charged, and the required time that is calculated in
5 S114. In this case, for example, a new amount of charging
current is calculated by using the following Equation 5.
[Mathematical Formula 5]
FULLY CHARGED v A. nn r % 1 _ SOC OF CHARGING ^
AMOUNT OF BATTERY CAPACITY [Ah] x \ 1 0 0 L % J SECONDARY BATTERY [%] j
CHARG NG CURKbN \A\ —•
REQUIRED TIME [A]
• - • (EQUATION 5)
[ 0 0 3 4 ]
10 In a d d i t i o n , the b a t t e r y c o n t r o l device 100 charges the
secondary b a t t e r y 210 with the amount of charging current
t h a t is c a l c u l a t e d by using the Equation 5 so as to r a i se
the charging current r a t e of the secondary b a t t e r y 210, and
then completes the charging in the required time•
15 [0035]
On the other hand, in a case where the total value is
equal to or greater than the predetermined number {YES in
S126), the battery control device 100 determines that it is
possible to prepare a necessary number of secondary batteries
20 210 in the fully charged state after passage of the required
time, and thus it is possible to secure the desired amount
of electric power. In this case, the battery control device
100 terminates the process without changing the charging
current rate of the charging secondary batteries 210.
25 [0036]
21
For example, the battery control device 100 executes
the above-described processes (S102 to S128) for each
predetermined interval, or for each time that is determined
in advance to control the charging current rate of each of
5 the secondary batteries 210.
[0037]
An example of raising the charging current rate by the
battery control device 100 will be described with reference
to FIG. 4. FIG. 4 is a view illustrating a flow of raising
10 the charging current rate by the battery control device 100.
[0038]
In FIG. 4, the required time of a secondary battery 210b
is "0.2 h", and the secondary battery 210b reaches the
constant battery capacity at the earliest time. In addition,
15 in only a secondary battery 210c, charging is completed in
0.2 h. That is, only in two secondary batteries including
the secondary battery 210c and a secondary battery 210f,
charging is completed after passage of 0.2 h. Accordingly,
it is necessary to complete charging of another secondary
20 battery so as to satisfy the predetermined number.
Accordingly, the battery control device 100 performs control
of raising a charging current rate of one of charging
secondary batteries 210d and 210e which do not reach the fully
charged state in the required time in order for charging
25 thereof to be completed in the required time. Here, the
battery control device 100 selects the secondary battery 210d
that is the closest to the fully charged state as a target
22
of which the charging current rate is to be raised. Here,
when a battery capacity of the fully charged secondary
battery 210d is set to 5 [Ah] , a new amount of charging current
of the secondary battery 210d which is calculated by using
5 Equation 5 becomes 5 [Ah]x(100-80) [%]/0.2 [h]-5 [A]. This
value is an amount of charging current with which the charging
current rate becomes "1 C" in the secondary battery 210d.
In addition, the battery control device 100 charges the
secondary battery 210d with an amount of charging current
10 with which a charging current rate becomes two times (1.0
C) the original current rate {0.5 C ) . According to this,
charging of the secondary battery 210d is completed in 0.2
h. Accordingly, when the secondary battery 210b reaches a
constant battery capacity, it is possible to prepare a
15 predetermined number of secondary batteries in the fully
charged state.
[0039]
As described above, in this exemplary embodiment, the
discharging current rate is calculated for each of the
20 discharging secondary batteries 210 on the basis of the
amount of discharging current that is measured by the
measurement unit 110. In addition, for each of the
discharging secondary batteries 210, the time, which is
required until the secondary battery reaches a predetermined
25 battery capacity, is calculated on the basis of the
discharging current rate of the discharging secondary
battery 210 which is calculated, and the SOC of the secondary
23
battery 210. In addition, the charging current rate is
calculated for each of the charging secondary batteries 210
on the basis of the amount of charging current of the charging
secondary battery 210. In addition, the expected number of
5 the secondary batteries 210 which becomes fully charged in
the required time is calculated on the basis of the calculated
charging current rate of the charging secondary battery 210,
the SOC of the secondary battery 210, and the required time.
In addition, it is determined whether or not a predetermined
10 number of secondary batteries 210 capable of securing a
desired amount of electric power can be prepared in the
required time on the basis of the expected number of the
secondary batteries 210 which becomes fully charged in the
required time that is calculated, and the existing number
15 of the secondary batteries which are already fully charged.
In addition, whether or not the charging current rate of the
charging secondary battery 210 is to be raised is controlled
on the basis of the determination result.
[0040]
20 As described above, according to this exemplary
embodiment, when the discharging secondary battery reaches
the constant battery capacity, it is possible to secure a
necessary number of secondary batteries in the fully charged
state, and it is possible to stably secure an amount of
25 electric power which a user desires.
[0041]
In addition, in this exemplary embodiment, the battery
24
control device 100 may raise the charging current rate of
secondary batteries 210 in order from one belonging to a
specific group that is set in advance. Here, the specific
group represents a group to which a secondary battery 210,
5 which is preferentially selected by the control unit 140 as
a target of which the charging current rate is to be changed,
belongs. In this case, in the process of S128, the battery
control device 100 selects a target of which the charging
current rate is to be raised among the secondary batteries
10 210 which do not become fully charged in the required time
and belong to the specific group.
[0042]
In addition, for example, the above-described specific
group can be classified on the basis of the state of health
15 {SOH) of each of the secondary batteries 210. For example,
the SOH can be calculated by using the following Equation
6.
[Mathematical Formula 6]
COH ro/i FULLY CHARGED BATTERY CAPACITY AT THE TIME OF DETERIORATION [Ah] . rtA
oUti Ivoj = X lUU
FULLY CHARGED INITIAL BATTERY CAPACITY [Ah]
. • .(EQUATION 6)
20 [0043]
Here, the range of the SOH which is determined as the
specific group is set by a user in an arbitrary manner. For
example, the battery control device 100 determines the
secondary battery 210, of which the SOH is in a range that
25 is equal to or greater than 70% and less than 90%, as the
25
above-described specific group. In addition, in a case
where the SOH of a predetermined secondary battery 210 is
equal to or greater than an upper limit of the range that
is determined as the specific group (90% in the
5 above-described range), the battery control device 100 may
determine that the secondary battery 210 belongs to a typical
charging group in which charging is typically performed with
a charging current rate in accordance with product
specifications. In addition, in a case where the SOH of the
10 predetermined secondary battery 210 is less than the lower
limit of the range that is determined as the specific group
(70% in the above-described range), the battery control
device 100 may determine that the secondary battery 210
belongs to a rapid charging group in which charging is
15 typically performed in a state in which the charging current
rate is raised. In this case, it is possible to tune the
power storage device 10 in accordance with a use, and thus
convenience is improved.
[0044]
20 (Second Exemplary Embodiment)
A second exemplary embodiment is substantially the same
as the first exemplary embodiment except for the following
configurations.
[0045]
25 In this exemplary embodiment, the number calculating
unit 130 determines whether or not the secondary battery 210
of which charging is completed before the passage of the
26
required time exists. Specifically, the number calculating
unit 130 calculates time (charging completion time) required
until charging is completed for each of the secondary
batteries 210 on the basis of the charging current rate and
5 the SOC of the charging secondary battery 210. In addition,
the number calculating unit 130 compares the calculated
charging completion time and the required time with each
other and determines whether or not the secondary battery
210 of which charging is completed before the passage of the
10 required time exists. In addition, the number calculating
unit 130 transmits the result to the control unit 140.
[0046]
In addition, the control unit 140 determines whether
or not to lower the amount of charging current of the
15 secondary battery 210 of which charging is completed before
the passage of the required time on the basis of the result
that is received from the number calculating unit 130.
[0047]
A process flow of the battery control device 100
20 according to this exemplary embodiment will be described with
reference to FIG. 5. FIG. 5 is a flowchart illustrating the
process flow of the battery control device 100 according to
the second exemplary embodiment.
[0048]
25 The battery control device 100 determines whether or
not a secondary battery 210, of which charging is completed
before the passage of the required time, exists among the
27
charging secondary batteries 210 (S202) . Specifically, in
S118, the battery control device 100 calculates the charging
completion time of the secondary battery 210 on the basis
of the charging current rate that is calculated in S118, and
5 the SOC, which is calculated in S120, of each of the charging
secondary batteries 210. In addition, the battery control
device 100 can determine whether or not charging of the
secondary battery 210 is completed before the passage of the
required time by comparing the calculated charging
10 completion time and the required time with each other. In
addition, in a case where the secondary battery 210 of which
charging is completed before the passage of the required time
exists (YES in S202), the battery control device 100 lowers
the charging current rate of the secondary battery 210
15 (S204) .
[0049]
Here, in the case of lowering the charging current rate,
the battery control device 100 may lower the charging current
rate of all secondary batteries 210 among the secondary
20 batteries 210 of which charging is completed before the
passage of the required time, or may lower the charging
current rate of parts of the secondary batteries 210 for
securement of electric power with a margin. In addition,
as is the case with the first exemplary embodiment, the
25 battery control device 100 can calculate a new charging
current rate by using Equation 4.
[0050]
28
On the other hand, in a case where the secondary battery
210 of which charging is completed before the passage of the
required time does not exist (NO in S202) , the battery control
device 100 terminates the process without changing the
5 charging current rate of the charging secondary batteries
210.
[0051]
An example of lowering the charging current rate by the
battery control device 100 will be described with reference
10 to FIG. 6. FIG. 6 is a view illustrating a flow of lowering
the charging current rate by the battery control device 100.
[0052]
In FIG. 6, the required time of a secondary battery 210b
is "0.2 h", and the secondary battery 210b reaches the
15 constant battery capacity at the earliest time. In addition,
in only a secondary battery 210c, charging is completed
before passage of 0.2 h. Here, when a battery capacity of
the fully charged secondary battery 210c is set to 5 [Ah],
a new amount of charging current of the secondary battery
20 210c which is calculated by using Equation 5 becomes 5
[Ah]x(100-95) [%]/0.2 [h]=1.25 [A]. This value is an amount
of charging current with which the charging current rate
becomes "0.25 C" in the secondary battery 210c. In addition,
the battery control device 100 charges the secondary battery
25 210c with an amount of charging current with which a charging
current rate (0.25 C) becomes 0.5 times the original charging
current rate (0.5 C) . According to this, even when lowering
29
the charging current rate, it is possible to prepare a
predetermined number of secondary batteries 210 in the fully
charged state in the required time.
[0053]
5 Hereinbefore, in this exemplary embodiment, the
charging completion time is calculated for each of the
secondary batteries 210 on the basis of the charging current
rate and the SOC of the charging secondary battery 210. In
addition, it is determined whether or not the secondary
10 battery 210, of which charging is completed before the
passage of the required time, exists on the basis of each
charging completion time that is calculated and the required
time. In addition, whether or not to lower the amount of
charging current of the secondary battery 210 of which
15 charging is completed before the passage of the required time
is controlled on the basis of the result.
[0054]
As described above, according to this exemplary
embodiment, it is possible to suppress deterioration of the
20 secondary batteries 210 while stably securing an amount of
electric power which a user desires.
[0055]
{Third Exemplary Embodiment)
A third exemplary embodiment is substantially the same
25 as the first exemplary embodiment or the second exemplary
embodiment except for the following configuration.
Hereinafter, description will be made on the basis of the
30
first exemplary embodiment.
[0056]
In general, the secondary batteries deteriorate when
repeating charging and discharging. Therefore, the battery
5 control device 100 of this exemplary embodiment weights the
number of the secondary batteries 210 in the fully charged
state in accordance with deterioration that occurs in
accordance with charging and discharging, and the like.
[0057]
10 FIG. 7 is a view illustrating a configuration example
of the battery control device 100 according to the third
exemplary embodiment. In this exemplary embodiment, the
number calculating unit 130 includes an SOH storage unit 132
and a weighting unit 134.
15 [0058]
The SOH storage unit 132 stores a deterioration state
(SOH) for each of the secondary batteries 210. FIG. 8 is
a view illustrating an example of information that is stored
in the SOH storage unit 132. In FIG. 8, information, which
20 is configured to individually identify each of the secondary
batteries 210 included in the battery section 200, is stored
in a column of identification information. Examples of the
identification information include a serial number of each
of the secondary batteries 210 and the like. In addition,
25 SOH of each of the secondary batteries 210 is stored in a
column of SOH. When charging of each of the secondary
batteries 210 is completed, for example, the SOH is
31
calculated by using Equation 6, and is stored in the SOH
storage unit 132. In addition, the SOH storage unit 132 may
be provided with other processing units other than the number
calculating unit 130, or other devices which are located at
5 the outside of the battery control device 100.
[0059]
The weighting unit 134 reads out the SOH from the SOH
storage unit 132 on the basis of the identification
information for each of the secondary batteries 210, and
10 weights the expected number and the existing number on the
basis of the SOH.
[0060]
A process flow of the battery control device 100
according to this exemplary embodiment will be described with
15 reference to FIG. 9. FIG. 9 is a flowchart illustrating the
process flow of the battery control device 100 according to
the third exemplary embodiment.
[0061]
In a case where the secondary batteries 210 as a target
20 are in a fully charged state (YES in S102), the battery
control device 100 adds the number of the secondary batteries
in the fully charged state, which is weighted on the basis
of the SOH, to the existing number (S302). Specifically,
the battery control device 100 reads out the SOH of the
25 secondary batteries 210 from the SOH storage unit 132 on the
basis of the identification information of the secondary
batteries 210 of which charging is already completed. In
32
addition, the battery control device 100 adds the number,
which is weighted on the basis of the SOH that is read out,
to the existing number that is stored in the existing number
storage unit 150. For example, in a case where plural pieces
5 of information illustrated in FIG. 8 are stored in the SOH
storage unit 132, and the identification information of the
secondary battery 210 of which charging is already completed
is "bbb", the battery control device 100 reads out "85%" as
the SOH of the secondary battery 210. In addition, the
10 battery control device 100 weights a value that is added to
the existing number on the basis of the SOH that is read out.
In this case, "1><85[%]^0.85 [pieces]" are added to the
existing number.
[0062]
15 In addition, the battery control device 100 calculates
an expected number of the secondary batteries which are fully
charged in the required time that is weighted on the basis
of the SOH (S304). Specifically, on the basis of the
identification information for each of the secondary
20 batteries 210 which becomes fully charged in the required
time, the battery control device 100 reads out the SOH of
the secondary battery 210 from the SOH storage unit 132. In
addition, the battery control device 100 adds the number that
is weighted on the basis of the SOH that is read out to
25 calculate the expected number. For example, in a case where
the plural pieces of information illustrated in FIG. 8 are
stored in the SOH storage unit 132, and the secondary
33
batteries 210 to which identification information "aaa" and
identification information "ccc" are given become fully
charged in the required time, the battery control device 100
reads out "100%" and "80%" as the SOH of the secondary
5 batteries 210. In addition, the battery control device 100
calculates the expected number on the basis of the SOH that
is read out. In this case, the expected number to be
calculated becomes "1x100 [%3+l*80 [%]=1.8 [pieces].
[0063]
10 As described above, according to this exemplary
embodiment, the expected number and the existing number are
weighted in accordance with a deterioration state for each
of the secondary batteries 210. In addition, it is
determined whether or not a predetermined number of secondary
15 batteries 210, which are capable of securing a desired amount
of electric power, are secured on the basis of a total value
of the expected number and the existing number which are
weighted. According to this, it is possible to further
stably secure an amount of electric power which a user
20 desires.
[0064]
Hereinbefore, the exemplary embodiments of the
invention have been described with reference to the
accompanying drawings, but these exemplary embodiments are
25 illustrative only, and various configurations other than the
above-described configuration can be employed. For example,
in the above-described exemplary embodiments, the battery
34
control device 100 may store a plurality of charging current
rates which are divided step by step, and in the case of
changing the charging current rates, a charging current rate,
with which charging can be completed in the required time,
5 may be selected.
[0065]
In addition, in the plurality of flowcharts which are
used in the description, a plurality of the processes are
sequentially described, but an execution sequence of the
10 processes which are executed in the exemplary embodiments
is not limited to the sequence described therein. For
example, in the exemplary embodiments, the sequence of the
processes which are illustrated may be changed within a range
not causing a problem in the contents thereof, for example,
15 the processes may be executed in combination with each other.
In addition, the exemplary embodiments can be combined with
each other within a range in which the contents thereof are
not contrary to each other.
[0066]
20 In addition, according to the above-described
exemplary embodiments, the following invention is disclosed.
(Additional Statement 1)
A battery control device including: a measurement unit
that individually measures an amount of discharging current
25 of a discharging secondary battery among a plurality of
secondary batteries which are independently charged and
discharged;
35
a time calculating unit that calculates time required
until the secondary battery has a constant battery capacity
for each of the discharging secondary batteries on the basis
of a discharging current rate for each of the secondary
5 batteries which is calculated on the basis of the amount of
discharging current, and a state of charge (SOC) of the
secondary battery;
a number calculating unit that calculates an expected
number of the secondary batteries, which become fully charged
10 in the required time, on the basis of a charging current rate
for each of the secondary batteries which is calculated on
the basis of an amount of charging current of the charging
secondary battery, the SOC of the secondary battery, and the
required time, and calculates a total value of the expected
15 number and the existing number of secondary batteries which
are already fully charged; and
a control unit that determines whether or not to raise
the charging current rate on the basis of the total value.
(Additional Statement 2)
20 The battery control device according Additional
Statement 1,
wherein the control unit raises the charging current
rate of the charging secondary batteries which do not become
fully charged in the required time in order from a secondary
25 battery that is closest to full charge.
{Additional Statement 3)
The battery control device according to Additional
36
Statement 1 or 2,
wherein the control unit raises the charging current
rate by an increment width of two or more times.
(Additional Statement 4)
5 The battery control device according to any one of
Additional Statements 1 to 3,
wherein the control unit lowers the charging current
rate on the basis of a charging completion time for each of
the charging secondary batteries, and the required time.
10 (Additional Statement 5)
The battery control device according to any one of
Additional Statements 1 to 4,
wherein the control unit raises the charging current
rate in order from a secondary battery belonging to a specific
15 group that is set as a target of which the charging current
rate is preferentially raised.
(Additional Statement 6)
The battery control device according to Additional
Statement 5,
20 wherein the specific group is classified on the basis
of a state of health (SOH) of each of the plurality of
secondary batteries.
(Additional Statement 7)
The battery control device according to any one of
25 Additional Statements 1 to 6,
wherein the number calculating unit weights the
expected number and the existing number on the basis of the
37
SOH for each of the plurality of secondary batteries.
(Additional Statement 8)
A power storage device, including:
a plurality of secondary batteries which are
5 independently charged and discharged;
a measurement unit that individually measures an amount
of discharging current of each of the discharging secondary
batteries;
a time calculating unit that calculates time required
10 until the secondary battery has a constant battery capacity
for each of the discharging secondary batteries on the basis
of a discharging current rate for each of the secondary
batteries which is calculated on the basis of the amount of
discharging current, and a state of charge (SOC) of the
15 secondary battery;
a number calculating unit that calculates an expected
number of the secondary batteries, which become fully charged
in the required time, on the basis of a charging current rate
for each of the secondary batteries which is calculated on
20 the basis of an amount of charging current of the charging
secondary battery, the SOC of the secondary battery, and the
required time, and calculates a total value of the expected
number and the existing number of secondary batteries which
are already fully charged; and
25 a control unit that determines whether or not to raise
the charging current rate on the basis of the total value.
(Additional Statement 9)
38
A power storage method, including allowing a computer
to:
individually measure an amount of discharging current
of a discharging secondary battery among a plurality of
5 secondary batteries which are independently charged and
discharged;
calculate time required until the secondary battery has
a constant battery capacity for each of the discharging
secondary batteries on the basis of a discharging current
10 rate for each of the secondary batteries which is calculated
on the basis of the amount of discharging current, and a state
of charge (SOC) of the secondary battery;
calculate an expected number of the secondary batteries,
which become fully charged in the required time, on the basis
15 of a charging current rate for each of the secondary batteries
which is calculated on the basis of an amount of charging
current of the charging secondary battery, the SOC of the
secondary battery, and the required time, and calculate a
total value of the expected number and the existing number
20 of secondary batteries which are already fully charged; and
determine whether or not to raise the charging current
rate on the basis of the total value.
(Additional Statement 10)
A program that allows a computer to function as:
25 a measurement unit that individually measures an amount
of discharging current of a discharging secondary battery
among a plurality of secondary batteries which are
39
independently charged and discharged;
a time calculating unit that calculates time required
until the secondary battery has a constant battery capacity
for each of the discharging secondary batteries on the basis
5 of a discharging current rate for each of the secondary
batteries which is calculated on the basis of the amount of
discharging current, and a state of charge (SOC) of the
secondary battery;
a number calculating unit that calculates an expected
10 number of the secondary batteries, which become fully charged
in the required time, on the basis of a charging current rate
for each of the secondary batteries which is calculated on
the basis of an amount of charging current of the charging
secondary battery, the SOC of the secondary battery, and the
15 required time, and calculates a total value of the expected
number and the existing number of secondary batteries which
are already fully charged; and
a control unit that determines whether or not to raise
the charging current rate on the basis of the total value.
20 (Additional Statement 11}
The power storage device according to Additional
Statement 8,
wherein the control unit raises the charging current
rate of the charging secondary batteries which do not become
25 fully charged in the required time in order from a secondary
battery that is closest to full charge.
(Additional Statement 12)
40
The power storage device according to Additional
Statement 8 or 11,
wherein the control unit raises the charging current
rate by an increment width of two or more times.
5 (Additional Statement 13)
The power storage device according to any one of
Additional Statements 8, 11, and 12,
wherein the control unit lowers the charging current
rate on the basis of a charging completion time for each of
10 the charging secondary batteries, and the required time.
{Additional Statement 14)
The power storage device according to any one of
Additional Statements 8, and 11 to 13,
wherein the control unit raises the charging current
15 rate in order from a secondary battery belonging to a specific
group that is set as a target of which the charging current
rate is preferentially raised.
(Additional Statement 15)
The power storage device according to Additional
20 Statement 14,
wherein the specific group is classified on the basis
of a state of health (SOH) of each of the plurality of
secondary batteries.
(Additional Statement 16)
25 The power storage device according to any one of
Additional Statements 8, and 11 to 15,
wherein the number calculating unit weights the
41
expected number and the existing number on the basis of the
SOH for each of the plurality of secondary batteries.
(Additional Statement 17)
The power storage method according to Additional
5 Statement 9,
wherein the computer raises the charging current rate
of the charging secondary batteries which do not become fully
charged in the required time in order from a secondary battery
that is closest to full charge.
10 (Additional Statement 18)
The power storage method according to Additional
Statement 9 or 17,
wherein the computer raises the charging current rate
by an increment width of two or more times.
15 (Additional Statement 19)
The power storage method according to any one of
Additional Statements 9, 17, and 18,
wherein the computer lowers the charging current rate
on the basis of a charging completion time for each of the
20 charging secondary batteries, and the required time.
(Additional Statement 20)
The power storage method according to any one of
Additional Statements 9, and 17 to 19,
wherein the computer raises the charging current rate
25 in order from a secondary battery belonging to a specific
group that is set as a target of which the charging current
rate is preferentially raised.
42
(Additional Statement 21)
The power storage method according to Additional
Statement 20,
wherein the specific group is classified on the basis
5 of a state of health (SOH) of each of the plurality of
secondary batteries.
(Additional Statement 22)
The power storage method according to any one of
Additional Statements 9, and 17 to 21,
10 wherein the computer weights the expected number and
the existing number on the basis of the SOH for each of the
plurality of secondary batteries.
(Additional Statement 23)
The program according to Additional Statement 10,
15 wherein the computer is allowed to function as a unit
that raises the charging current rate of the charging
secondary batteries which do not become fully charged in the
required time in order from a secondary battery that is
closest to full charge.
20 (Additional Statement 24)
The program according to Additional Statement 10 or 23,
wherein the computer is allowed to function as a unit
that raises the charging current rate by an increment width
of two or more times.
25 (Additional Statement 25)
The program according to any one of Additional
Statements 10, 23, and 24,
43
wherein the computer is allowed to function as a unit
that lowers the charging current rate on the basis of a
charging completion time for each of the charging secondary
batteries, and the required time.
5 (Additional Statement 26)
The program according to any one of Additional
Statements 10, and 23 to 25,
wherein the computer is allowed to function as a unit
that raises the charging current rate in order from a
10 secondary battery belonging to a specific group that is set
as a target of which the charging current rate is
preferentially raised.
{Additional Statement 27)
The program according to Additional Statement 26,
15 wherein the computer is allowed to function as a unit
that classifies the plurality of secondary batteries into
specific groups on the basis of a state of health (SOH) of
each of the plurality of secondary batteries.
{Additional Statement 28)
20 The program according to any one of Additional
Statements 10, and 23 to 27,
wherein the computer is allowed to function as a unit
that weights the expected number and the existing number on
the basis of the SOH for each of the plurality of secondary
25 batteries.
[0067]
The present patent application claims priority from
44
Japanese Patent Application No. 2012-247572 filed on
November 9, 2012, the disclosure of which is incorporated
herein by reference.

CLAIMS
1. A battery control device, comprising:
a measurement unit that individually measures an amount
of discharging current of a discharging secondary battery
among a plurality of secondary batteries which are
5 independently charged and discharged;
a time calculating unit that calculates time required
until the secondary battery has a constant battery capacity
for each of the discharging secondary batteries on the basis
of a discharging current rate for each of the secondary
10 batteries which is calculated on the basis of the amount of
discharging current, and a state of charge (SOC) of the
secondary battery;
a number calculating unit that calculates an expected
number of the secondary batteries, which become fully charged
15 in the required time, on the basis of a charging current rate
for each of the secondary batteries which is calculated on
the basis of an amount of charging current of the charging
secondary battery, the SOC of the secondary battery, and the
required time, and calculates a total value of the expected
20 number and the existing number of secondary batteries which
are already fully charged; and
a control unit that determines whether or not to raise
the charging current rate on the basis of the total value.
2. The battery control device according to claim 1,
46
wherein the control unit raises the charging current
rate of the charging secondary batteries which do not become
fully charged in the required time in order from a secondary
5 battery that is closest to full charge.
3. The battery control device according to claim 1 or 2,
wherein the control unit raises the charging current
rate by an increment width of two or more times.
4 . The battery control device according to any one of claims
1 to 3,
wherein the control unit lowers the charging current
rate on the basis of a charging completion time for each of
5 the charging secondary batteries, and the required time.
5. The battery control device according to any one of claims
1 to 4,
wherein the control unit raises the charging current
rate of the charging secondary batteries which do not become
5 fully charged in the required time in order from a secondary
battery that is closest to full charge.
6. The battery control device according to claim 5,
wherein the specific group is classified on the basis
of a state of health (SOH) of each of the plurality of
secondary batteries.
47
7 . The battery control device according to any one of claims
1 to 6,
wherein the number calculating unit weights the
expected number and the existing number on the basis of the
5 SOH for each of the plurality of secondary batteries.
8. A power storage device, comprising:
a plurality of secondary batteries which are
independently charged and discharged;
a measurement unit that individually measures an amount
5 of discharging current of each of the discharging secondary
batteries;
a time calculating unit that calculates time required
until the secondary battery has a constant battery capacity
for each of the discharging secondary batteries on the basis
10 of a discharging current rate for each of the secondary
batteries which is calculated on the basis of the amount of
discharging current, and a state of charge (SOC) of the
secondary battery;
a number calculating unit that calculates an expected
15 number of the secondary batteries, which become fully charged
in the required time, on the basis of a charging current rate
for each of the secondary batteries which is calculated on
the basis of an amount of charging current of the charging
secondary battery, the SOC of the secondary battery, and the
20 required time, and calculates a total value of the expected
number and the existing number of secondary batteries which
48
are already fully charged; and
a control unit that determines whether or not to raise
the charging current rate on the basis of the total value.
9. A power storage method, comprising allowing a computer
to:
individually measure an amount of discharging current
of a discharging secondary battery among a plurality of
5 secondary batteries which are independently charged and
discharged;
calculate time required until the secondary battery has
a constant battery capacity for each of the discharging
secondary batteries on the basis of a discharging current
10 rate for each of the secondary batteries which is calculated
on the basis of the amount of discharging current, and a state
of charge (SOC) of the secondary battery;
calculate an expected number of the secondary batteries,
which become fully charged in the required time, on the basis
15 of a charging current rate for each of the secondary batteries
which is calculated on the basis of an amount of charging
current of the charging secondary battery, the SOC of the
secondary battery, and the required time, and calculate a
total value of the expected number and the existing number
20 of secondary batteries which are already fully charged; and
determine whether or not to raise the charging current
rate on the basis of the total value.
49
10. A program that allows a computer to function as:
a measurement unit that individually measures an amount
of discharging current of a discharging secondary battery
among a plurality of secondary batteries which are
independently charged and discharged;
a time calculating unit that calculates time required
until the secondary battery has a constant battery capacity
for each of the discharging secondary batteries on the basis
of a discharging current rate for each of the secondary
batteries which is calculated on the basis of the amount of
discharging current, and a state of charge (SOC) of the
secondary battery;
a number calculating unit that calculates an expected
number of the secondary batteries, which become fully charged
in the required time, on the basis of a charging current rate
for each of the secondary batteries which is calculated on
the basis of an amount of charging current of the charging
secondary battery, the SOC of the secondary battery, and the
required time, and calculates a total value of the'expected
number and the existing number of secondary batteries which
are already fully charged; and
a control unit that determines whether or not to raise
the charging current rate on the basis of the total value.