Technical Field
[OOOl] The present technology relates to a power
storage system that performs power storage using a
secondary battery such as a lithium-ion battery and to
a charging method for a secondary battery.
Background Art
[0002] Currently, secondary batteries represented by
lithium-ion batteries or the like are widely used as
power supplies for various mobile devices such as a
mobile phone. In recent years, there is a great market
demand to increase the capacity of power storage
batteries for onboard use in electric automobiles and
hybrid vehicles, large-size power storage use of back
up power supplies of mobile phone base stations and the
like, and middle-size power storage use of household
back'-up ,porier supplies, for example. Accordingly, it is
expected that the opportunity to constantly use the
secondary battery outdoors will increase. Therefore,
there is a growing tendency to consider the temperature
characteristics of the secondary battery as important.
[00031 In particular, at a low temperature, the
characteristics of the lithium-ion battery are lowered
and the deterioration progresses rapidly. The
deterioration of the secondary battery is classified
into a plurality of modes depending on conditions. For
example, a lithium-ion battery is slowly deteriorated
5 at a temperature equal to or higher than a room
temperature (e.g., 15Co or more) and rapidly
deteriorated due to precipitation of metal lithium at a
temperature lower than the room temperature
[0004] As a publicly known technique for monitoring
10 the deterioration state of the secondary battery, for
example, there is known a technique for estimating an
amount of deterioration based on a square root of time,
a temperature, and a state of charge (SOC) (e.g.,
Patent Document 1). Such a technique is configured to
15 estimate a slow deterioration state at a temperature
equal to or higher than a room temperature.
[0005] Patent Document 1: Japanese Patent
Application Laid-open No. 2007-195312
Summary of Invention
2 0 Problm~-t~-~be-'solbvye dt he Invention
[OO061 The deterioration mode of the lithium-ion
battery at least includes slow deterioration at a
temperature equal to or higher than a room temperature
(e.g., 15Co or more) and rapid deterioration due to
25 precipitation of metal lithium at a temperature lovrer
than the room temperature. The rapid deterioration due
to precipitation of metal lithium at the temperature
lower than the room temperature largely influences the
lifetime of the lithium-ion battery. The rapid
deterioration at a temperature lower than the room
temperature can be suppressed by some degree by
reducing a charging current.
However, if the charging current is reduced, a
longer charging time is correspondingly required, which
impairs the convenience for an end user. If the
charging current is increased for shortening the
charging time, the rapid deterioration due to
precipitation of metal lithium at a temperature lower
than the room temperature becomes more significant with
the result that the lifetime is shortened.
[0007] As described above, in the secondary battery
such as a lithium-ion battery, there is a problem in
that it is difficult to select a charging condition
such as an optimal charging current.
[0008] In view of this, it is an object of the
20 present eechnology to provide a power storage system
capable of charging a secondary battery in an optimal
charging condition and a charging method for a
secondary battery.
Means for solving the Problem
25 [0009] In order to solve the above-mentioned
problem, a power storage system according to an aspect
of the present technology includes: a parameter
detector that detects a parameter of a secondary
battery; a table storage unit that stores a table
indicating a correspondence between a parameter of the
5 secondary battery and a charging condition; and a
charging control unit configured to refer to, based on
the detected parameter, a corresponding charging
condition from the table and make control to charge the
secondary battery in this charging condition.
[OOlO] The table may be a table showing a
correspondence between a combination of the temperature
of the secondary battery with an internal resistance
and a charging condition.
[OOll] The charging condition may be defined to
ensure a predetermined use period of the secondary
battery.
[00121 The charging control unit may be configured
to refer to the corresponding charging condition from
the table and perform charging in this charging
condition if the detected temperature is lower than a
predetermined temperature, and to perform charging in a
fixed charging condition if the detected temperature is
equal to or higher than the predetermined temperature.
[00131 This power storage system further includes:
an amount-of-deterioration calculator that calculates
an amount of deterioration of the secondary battery;
and an allowable amount-of-deterioration calculator
that calculates an allowable amount of deterioration of
the secondary battery, in which the charging control
unit may be configured to compare the calculated amount
of deterioration with the calculated allowable amount
of deterioration and to update the charging condition
of the table such that the deterioration speed of the
secondary battery is suppressed according to a result
thereof.
[00141 The amount-of-deterioration calculator and
the allowable amount-of-deterioration calculator may
calculate the amount of deterioration and the allowable
amount of deterioration, respectively, according to a
predetermined timing condition, and the charging
control unit may be configured to update, if a change
value of the amount of deterioration that is next
acquired with respect to the amount of deterioration at
a point of time at which the charging condition of the
table was updated is larger than a change value of the
allovrzbPe amount of deterioration that is next acquired
with respect to the allowable amount of deterioration
at the point of time at which the charging condition of
the table was updated, the charging condition of the
table such that a deterioration speed of the secondary
battery is reduced.
[00151 A charging method for a secondary battery
according to another aspect of the present technology
includes: detecting a parameter of the secondary
battery; referring to a corresponding charging
condition from a table showing a correspondence between
5 the parameter of the secondary battery and the charging
condition based on the detected parameter; and charging
the secondary battery in this charging condition.
Effects of the Invention
[0016] As described above, according to the present
10 technology, it is possible to charge the secondary
battery in the optimal charging condition.
Brief Description of Drawings
[0017] [Fig. 11 A block diagram showing a
configuration of a power storage system that is a first
15 embodiment according to the present technology.
[Fig. 21 A diagram showing an example of a
table showing a correspondence between a combination of
a temperature of a secondary battery with an internal
resistance and a charging condition.
20 . ". - [Fig. 31 A diagram describing an OCV
capacity .
[Fig. 41 A graph showing a relationship
between a total operating time t, and an allowable
Qner(t,) of the secondary
2 5 battery.
[Fig. 51 A flowchart showing a flow of
selection processing of a charging condition.
[Fig. 61 A flowchart showing a flow of
updating a table.
[Fig. 71 A diagram showing an example of an
5 update result of the table.
[Fig. 81 A diagram showing a case where, in
the determination as to whether or not second or
subsequent update of the table is necessary, it is
determined that the update is not necessary.
[Fig. 91 A diagram showing a case where, in
the determination as to whether or not second or
subsequent update of the table is necessary, it is
determined that the update is necessary.
[Fig. 101 A diagram showing a tl-second
15 resistance used as a deterioration index of the
secondary battery.
Mode(s) for Carrying Out the Invention
[0018] Hereinafter, an embodiment of the present
technology will be referred with reference to the
drac7iliqs. ,',

[0019] Fig. 1 is a block diagram showing a
configuration of a power storage system that is a first
embodiment according to the present technology.
The power storage system 100 includes a secondary
battery module 1, a charging control apparatus 2, and a
charging unit 3.
[00201 The secondary battery module 1 is, for
example, formed of a secondary battery such as a
lithium-ion battery.
5 [00211 The charging control apparatus 2 is an
apparatus that controls the charging unit 3.
The charging unit 3 is formed of a circuit or the
like for generating, from a power obtained from an
apparatus or the like that converts a commercial porsrer
10 supply or solar energy into a power, a power for
charging the secondary battery, and supplying it into
the secondary battery.
[00221 The charging control apparatus 2 includes a
deterioration parameter acquisition unit 10 that
15 acquires values of a plurality of deterioration
parameters necessary to determine an amount of
deterioration or the like of the secondary battery in
the secondary battery module 1.
[00231 The deterioration parameter acquisition unit
10 knc3udes a current monitoring unit 11 that monitors
a current flowing through the secondary battery during
charging by the use of a current sensor or the like, a
voltage monitoring unit 12 that monitors a voltage
across terminals of the secondary battery during
charging by the use of a voltage sensor or the like, a
time monitoring unit 13 that monitors a total operating
time of the secondary battery by the use of a timer or
the like, and a temperature monitoring unit 14 that
captures and monitors information on the temperature of
the secondary battery from a temperature sensor or the
like in the secondary battery module 1. That is, the
deterioration parameter acquisition unit 10 acquires a
current flowing through the secondary battery during
charging, a voltage across the terminals of the
secondary battery during charging, a total operating
time of the secondary battery, and a temperature of the
secondary battery as the values of the deterioration
parameters.
[a0241 The charging control apparatus 2 further
includes a use history storage unit 21, a deterioration
index calculator 22, an allowable deterioration index
calculator 23, a resistance calculator 24, a charging
condition table storage unit 25, and a charging control
unit 26. Here, the use history storage unit 21 and the
charging condition table storage unit 25 are storage
unit.3 prwrided using a memory device such as a RAM
(Random Access Memory) (not shown) in the charging
control apparatus 2.
The deterioration index calculator 22, the
allowable deterioration index calculator 23, the
resistance calculator 24, and the charging control unit
26 are functional units provided as a controller such
as a CPU (Central Processing Unit), a program, and the
like in the charging control apparatus 2.
[00251 The use history storage unit 21 is an area
for storing the values of the deterioration parameters
such as a current, a voltage, a total operating time,
and a temperature that are acquired by the
deterioration parameter acquisition unit 10 as a use
history of the secondary battery.
[00261 The charging condition table storage unit 25
is, for example, as shown in Fig. 2, an area in which a
table showing the correspondence between the
combination of the temperature of the secondary battery
with the internal resistance and the charging condition
is stored. The internal resistance of the secondary
battery is gradually increased due to deterioration of
the secondary battery. Therefore, by combining it with
the temperature of the secondary battery, it becomes
possible to select the charging condition at a higher
resolution.
[0027]- In this embodiment, the charging condition is
provided as a charging current. At a temperature lower
than a room temperature, as the charging current is
lowered, the deterioration speed of the secondary
battery can be suppressed. However, as the charging
current is lowered, a longer charging time is required.
In view of this, in order to make the charging time as
short as possible in such a range that a use period of
the secondary battery required by a maker or the like
can be ensured, information indicating an optimal
charging current with respect to a combination of
values of the temperature and the internal resistance
of the secondary battery is set in the table.
[00281 Note that, in the table shown in Fig. 2, the
temperature 20C0 indicates a range of 15C0 or more and
less than 25C0. The temperature 10Co indicates a range
of 5C0 or more and less than 15C0. The temperature OCo
indicates a range of -0.25Co or more and less than 5C0.
The temperature -5C0 indicates a range of -xCo or more
and less than -0.25C0. Furthermore, the resistance
value 20 mQ indicates 25 mQ or less. The resistance
value 30 mQ indicates 25 mQ or more and less than 3 5 mQ.
The resistance value 40 mQ indicates 35 mQ or more and
less than 45 ma. The resistance value 50 mQ indicates
4 5 mQ or more and less than 5 5 ma.
100291 The temperature, the resolution of the
internal resistance, and the information indicating a
charging current that are shown in the table are
examples. In some combinations of the values of the
temperature and the internal resistance, a case where
charging itself is impossible is assumed. With respect
to such combinations, information indicating charging
inhibition is set.
[0030] Based on the values of the deterioration
parameters such as current, voltage, and total
operating time that are stored in the use history
storage unit 21, the deterioration index calculator 22
calculates a deterioration index value Q(t,) indicating
an amount of deterioration of the secondary battery at
the current point of time (point of time of total
operating time t,).
[00311 The allowable deterioration index calculator
23 determines an allovrable deterioration index value
Q~,f(t,) corresponding to the total operating time t, of
the secondary battery that is used as the evaluation
reference value of the deterioration index value Q(t,)
at a point of time of the total operating time t, that
is calculated by the deterioration index calculator 22.
[0032] There are various types of deterioration
index of the secondary battery. One of them is, for
example, an OCV (Open Circuit Voltage) capacity. The
OCV capacity is originally an integrated capacity when
dischsrge and stop of the secondary battery are
repeated from its fully charged state until it reaches
a cut-off voltage as shown in Fig. 3
It is assumed that a charging capacity calculated
by, for example, multiplication of a charging current
and a time after the secondary battery is completely
discharged at a low current until the fully charged
state is obtained is approximately equal to the above
mentioned OCV capacity. It is thus possible to adopt
this as the deterioration index of the secondary
battery.
[OO33] Fig. 4 is a graph showing a relationship
betvieen the allowable deterioration index value Qef(tn)
and the total operating time t, of the secondary battery
in the case where the above-mentioned OCV capacity is
adopted as the deterioration index value Q(t,).
Information indicating this relationship is stored in
the allowable deterioration index calculator 23 in
advance. The allobrable deterioration index calculator
23 determines, based on this information, the allowable
deterioration index value Q,f(t,) at the point of time
of the total operating time t,.
[OD341 The resistance calculator 24 statistically
calculates an internal resistance corresponding to the
deterioration state of the secondary battery by the use
of the values of the deterioration parameters such as
current, vwltage, and time stored in the use history
storage unit 21, to which a measurement time
corresponds, and stores that value.
Note that, in this embodiment, the deterioration
parameter acquisition unit 10 and the resistance
calculator 24 correspond to a "parameter detector" in
the scope of claims.
to0351 The charging control unit 26 is a controller
that controls charging of the secondary battery. When a
predetermined timing condition is established, the
charging control unit 26 refers to the value of the
5 parameter of the temperature stored in the use history
storage unit 21 and acquires the value of the internal
resistance of the secondary battery stored in the
resistance calculator 24. The charging control unit 26
refers to the charging condition corresponding to the
10 combination of the temperature with the internal
resistance and sets it inside the charging control unit
26.
100361 The charging control unit 26 compares the
deterioration index value Q(tn) at the point of time of
15 the total operating time t, that is calculated by the
deterioration index calculator 22 with the allowable
deterioration index value QRef(t,) at the point of time
of the total operating time t, that is calculated by the
allowable deterioration index calculator 23, to thereby
evalue'te the deterioration state of the secondary
battery.
[00371 If Q(t,)>QRef(t,) is not established, that is,
if the deterioration index value Q(t,) is equal to or
smaller than the allowable deterioration index value
QRef(t,), it is determined that the amount of
deterioration of the secondary battery is in such a
range that a use period required by a maker or the like
cannot be ensured. In this case, the charging control
unit 26 updates the charging condition of the table
such that the deterioration speed of the secondary
battery is suppressed.
[00381 Furthermore, if an amount of change (amount
of decrease) of a next calculated deterioration index
value Q(t,) with respect to the deterioration index
value Q(tn-1) at the point of time at which the charging
condition of the table was updated is larger than a
change value (amount of decrease) of a next calculated
allowable deterioration index value Qnef(t,) with respect
to the allowable deterioration index value Q~,r(t,-l)
also at the point of time at which the charging
condition of the table was updated, the charging
control unit 26 is configured to update the charging
condition of the table such that the deterioration
speed of the secondary battery is reduced, again.
[00391 [Description of Operation]
Next, an operation of the charging control
apparatus 2 of this embodiment will be described.
[0040] (1. Storage of Use History of Secondary
Battery and Value of Internal Resistance)
The deterioration parameter acquisition unit 10
acquires, during charging of the secondary battery
module 1, values of deterioration parameters of current,
voltage, total operating time, and temperature. The
deterioration parameter acquisition unit 10 may acquire,
for example, during charging of the secondary battery
module 1, the values of the deterioration parameters at
the same or approximately the same timing one or more
times
The acquired values of the deterioration
parameters are stored as a use history in the use
history storage unit 21. If, during charging, the
values of the deterioration parameters are acquired a
plurality of times and stored in the use history
storage unit 21, an average value of those values may
be used for calculating internal resistance,
deterioration index value, and the like.
[00411 Furthermore, the resistance calculator 24
refers to, according to a predetermined timing
condition, the values of the deterioration parameters
of the current, voltage, time, and the like from the
use history storage unit 21, calculates an internal
respstance of the secondary battery or an average value
thereof, and stores the result. Note that examples of a
timing condition for calculating the internal
resistance can include immediately after the end of
charging.
[0042] (2. Selection of Charging Condition at
Temperature Lower than Room Temperature)
Fig. 5 is a flo~rchart showing a flow of selection
processing of the charging condition.
[00431 First, the charging control unit 26 of the
charging control apparatus 2 is provided with an
instruction to start charging by, for example, a highorder
controller. When receiving the instruction to
start charging, the charging control unit 26 acquires
the value of the deterioration parameter that is the
temperature stored in the use history storage unit 21
(Step S101).
[00441 Next, the charging control unit 26 compares
the acquired temperature with a predetermined specified
temperature (Step S202). The specified temperature may
be, for example, 25C0. The present technology is not
limited to this temperature as a matter of course.
[0045] Note that the charging control unit 26 may
acquire, from the use history storage unit 21, values
of the temperature at a plurality of points of time
within a certain period and compare an average value of
the wa'lues of the temperature with the specified
temperature
[0046] If the acquired temperature (or the average
value) is equal to or higher than the specified
temperature (No in Step S102), the charging control
unit 26 considers that there is a low possibility that
the rapid deterioration due to precipitation of metal
lithium occurs, and issues a charging control
instruction to the charging unit 3 to start charging of
the secondary battery in a predetermined fixed charging
condition (Step 5103). Thus, the fixed charging
5 condition used in an environment at a temperature equal
to or higher than the specified temperature is set in
advance other than the variable charging conditions
managed by the table
I00471 If the acquired temperature (or the average
value) is lower than the specified temperature (Yes in
Step S102), the charging control unit 26 proceeds to
processing of referring to the table and selecting a
charging condition. First, the charging control unit 26
acquires a value of the internal resistance of the
secondary battery that is stored in the resistance
calculator 24 (Step S104) .
I00481 Next, the charging control unit 26 refers to
a charging condition associated with a combination of
the acquired value of the temperature with the value of
the internal resistance, from the table (Step S105).
For example, assuming the table shown in Fig. 2, if the
temperature is 19C0 and the resistance value is 32 ma,
0.8C is selected as the charging condition. Here, 1C
means a current value by which the secondary battery is
discharged at a constant current and the discharging is
completed one time.
[0049] The charging control unit 26 provides the
charging unit 3 with the charging control instruction
to start charging of the secondary battery in the
charging condition referred from the table (Step S106)
5 According to this charging control instruction, the
charging unit 3 starts charging of the secondary
battery in that charging condition.
[OOSO] Note that there is a case where, with respect
to the combination of the temperature with the internal
resistance, the information indicating the charging
inhibition is referred from that table. In this case,
the charging control unit 26 performs processing during
charging inhibition, for example, the processing of
supplying a control instruction for charging inhibition
to the charging unit 3 and notifying the user of it.
With this, it is possible to avoid occurrence of an
accident or the like due to unexpected use of the
secondary battery.
[0051] Also during charging of the secondary battery,
the 'charging control unit 26 acquires, for example, in
a predetermined certain time period (Step S 1 0 7 ) , the
value of the temperature from the use history storage
unit 21 and the value of the internal resistance from
the resistance calculator 24 (Step S 1 0 9 ) .
The charging control unit 26 refers to the
charging condition associated with the combination of
the values of the acquired temperature and the internal
resistance from the table (Step S110) and determines
whether or not the referred charging condition is
different from the charging condition already set in
5 the charging unit 3 (Step S111).
[0052] If the charging condition referred from the
table is the same as the charging condition already set
in the charging unit 3 (No in Step Sill), the charging
control unit 26 returns to the processing of Step 5107
10 of waiting for elapse of the certain time and repeats
the same procedure.
[00531 If the newly referred charging condition is
different from the already adopted charging condition
(Yes in Step Sill), the charging control unit 26
15 provides the charging unit 3 with a charging condition
changing instruction to change to the newly referred
charging condition (Step S112). The charging unit 3
changes the charging condition according to this
charging condition changing instruction.
I00541 (3. Table Updating Processing According to
Amount of Deterioration of Secondary Battery)
Fig. 6 is a flowchart showing a flow of table
updating processing.
If charging of the secondary battery ends in Step
S108 of Fig. 5 (Yes in Step S108), the charging control
unit 26 activates the deterioration index calculator 22
and the allowable deterioration index calculator 23 for
performing the table updating processing according to
the amount of deterioration of the secondary battery.
LOO551 The deterioration index calculator 22 refers
to the values of the deterioration parameters of the
current, voltage, total operating time, and the like
that are stored in the use history storage unit 21 and
calculates the deterioration index value Q(t,) of the
secondary battery at the current point of time (point
of time of the total operating time t,) (Step 5201).
[00561 Next, the allowable deterioration index
calculator 23 calculates an allowable deterioration
index value QRef(tn) used as a reference value for
evaluating the deterioration index value Q(tn) in the
total operating time t, (Step 5202).
[0057] After the allowable deterioration index value
QRef(t,) is calculated, the charging control unit 26
confirms a table update history (Step 5203). The table
update history includes information indicating whether
or not the charging condition of the table has been
updated, update date and time, and the like.
[0058] If it is confirmed that the charging
condition of the table has not been updated (Yes in
Step S203), the charging control unit 26 acquires the
deterioration index value Q(t,) from the deterioration
index calculator 22 and acquires the allowable
deterioration index value QRef(t,) from the allowable
deterioration index calculator 23. The charging control
unit 26 compares the deterioration index value Q(t,)
with the allov~able deterioration index value Q~,f(t,) and
determines whether or not the. following condition is
satisfied (Step 5204).
Q(tn) >Q~ef( tn) ...(I)
[0059] If the condition of Expression (1) above is
satisfied (Yes in Step S204), the charging control unit
26 considers that the deterioration state of the
secondary battery is at a level such that no problem
occurs even if the current charging condition of the
table is used as it is, in other words, at a level such
that the use period of the secondary battery that is
set by the maker or the like can be ensured, and
terminates the processing. Note that the relationship
between the deterioration index value Q(t,) and the
allowable deterioration index value QRef( tn) of Fig. 4
satisfies the condition of Expression (1) above.
[0060] If the condition of Expression (1) above is
not satisfied (No in Step S204), the charging control
unit 26 considers that the deterioration state of the
secondary battery has a problem if the contents of the
current table are used (there is a possibility that the
use period of the secondary battery that is determined
by the user cannot be ensured), and updates the
charging condition of the table so as to increase the
possibility that the use period of the secondary
battery that is required by the maker or the like can
be ensured (Step 5205).
[OO61] As a method of updating the charging
condition of the table, for example, if the charging
condition is a charging current, there is, for example,
a method of multiplying the value of each charging
current by a predetermined value below the decimal
point. For example, the value of 0.9 is adopted as a
fixed value below the decimal point. With this, the
contents of the table are updated from the state shown
in Fig. 2 to that of Fig. 7. Here, the use of the
combination of the temperature with the resistance
value by which the current value is smaller than 0.1C
may be inhibited.
LOO621 After first update of the table is performed,
the charging control unit 26 records the table update
history (Step S206).
[00631 Next, a case where it is in Step S203
determined that the table has been updated will be
described (Yes in Step S203). The charging control unit
26 determines whether or not the following condition is
satisfied (Step S207).
Q(tn-l)-Q(tn)>Q~ef(tn-~)-Q~ef(tn) ... (2)
Where Q(tn.~) denotes a deterioration index value
calculated for the previous update of the table and
Qnef(tn-1) denotes an allowable deterioration index value
calculated for the previous update of the table.
[0064] If the condition of Expression (2) above is
5 not satisfied (No in Step 52071, the charging control
unit 26 considers that the deterioration speed of the
secondary battery has no problem even if the current
table is used as it is, that is, the deterioration
speed of the secondary battery is at a level such that
the use period of the secondary battery can be ensured,
and terminates the processing.
[00651 Fig. 8 shows an example in the case where the
condition of Expression (2) is not satisfied. The
amount of decrease (Q (t,-1) -Q (t,) ) of the deterioration
index value is smaller than the amount of decrease
(QR.(~t ,-~)- Qnef(tn)) of the allowable deterioration index
value. Therefore, there is a low possibility that the
deterioration index value Q(t,) may be lovier than the
allov~able deterioration index value Q,f(t,) in the
future,;--,.Thiast, by using the current table as it is,
it is estimated that the use period of the secondary
battery can be ensured
[00661 If thecondition of Expression (2) above is
satisfied (Yes in Step S207), the charging control unit
26 considers that the deterioration speed of the
secondary battery is at a level such that a problem
occurs if the contents of the current table are used,
in other words, at a level such that the use period of
the secondary battery cannot be ensured, and updates
the charging condition of the table such that there is
5 a higher possibility that the use period of the
secondary battery that is required by the maker or the
like can be ensured (Step S205).
[00671 Fig. 9 shows an example in the case where the
condition of Expression (2) is not satisfied. The
amount of decrease (Q (t,-1) -Q (t,) ) of the deterioration
index value is larger than the amount of decrease
(QRef(t ,.~) -Qnef(t ,) ) of the allowable deterioration index
value. Therefore, there is a possibility that the
deterioration index value Q(tn) may be lower than the
allowable deterioration index value QRef(tn) in the
future. That is, if the current table is used as it is,
it is estimated that there is a possibility that the
use period of the secondary battery cannot be ensured.
Thus, in such a case, the table is updated such that
20 . there4s a higher possibility that the use period of
the secondary battery that is required by the maker or
the like can be ensured.
[0068] In this case, as a method of updating the
table, as in the first update, for example, if the
charging condition is a charging current, a method of
multiplying the value of each charging current by a
predetermined value below the decimal point may be used.
Alternatively, the charging condition of the table may
be updated by a method different from that in the first
update.
5 [00691 After the table is updated, the charging
control unit 26 records the table update history again
(Step S206).
[0070] [Effects, etc. of This Embodiment]
1. In the power storage system 100 of this
10 embodiment, with respect to various combinations of the
temperature of the secondary battery with the internal
resistance, the charging control apparatus 2 includes a
table in which an ideal charging condition is
registered in view of two perspectives of the reduction
of the deterioration speed of the secondary battery at
the temperature lower than the room temperature and the
charging time. The charging control unit 26 refers to
an ideal charging condition corresponding to the
temperature of the secondary battery and the internal
resistance at the current point of time from the table
and makes a control to perform charging in this
charging condition. With this, it is possible to charge
the secondary battery in the optimal charging condition
in view of two perspectives of the reduction of the
deterioration speed of the secondary battery at the
temperature lower than the room temperature and the
charging time.
[00711 2. The charging control unit obtains an ideal
charging condition from the table also during charging
of the secondary battery and changes the charging
condition depending on needs. That is, it is possible
to operationally charge the secondary battery in an
optimal charging condition depending on a change in
situation.
LOO721 3. The deterioration index calculator 22
quantifies the amount of deterioration of the secondary
battery as the deterioration index value Q(t,) at the
point of time of the total operating time t,. If the
deterioration index value Q(t,) at the point of time of
the total operating time t, becomes equal to or smaller
than the allowable deterioration index value Q~~f(t,,a)t
the point of time of the total operating time t,, the
charging control unit 26 determines that the
deterioration state of the secondary battery is in such
a range that the use period required by the maker or
the like cannot be ensured, and updates the charging
condition of the table such that the deterioration
speed of the secondary battery at the temperature lower
than the room temperature is reduced. With this, it is
possible to charge the secondary battery in the optimal
charging condition in view of three perspectives of the
reduction of the deterioration speed of the secondary
battery at the temperature lower than the room
temperature, a charging time, and further a required
use period.
[0073] 4. In addition, if the amount of change
(amount of decrease) of the deterioration index value
Q(t,) next calculated with respect to the deterioration
index value Q(t,.l) at the point of time at which the
charging condition of the table was updated is larger
than the change value (amount of decrease) of the
allowable deterioration index value Q~~f(t,)n ext
calculated also with respect to the allowable
deterioration index value QRef(tn-l) at the point of time
at which the charging condition of the table was
updated, the charging control unit 26 updates the
charging condition of the table such that the
deterioration speed of the secondary battery is
suppressed, again. Also with this, it is possible to
charge the secondary battery in the optimal charging
condition in view of three perspectives of the
reduct'ion of the deterioration speed of the secondary
battery at the temperature lower than the room
temperature, the charging time, and further the
required use period.
[00741
In the above-mentioned embodiment, the charging
condition is set as a charging current. However, there
can be exemplified a cut-off current and a cut-off
voltage when charging is terminated, as the charging
condition that can be also used. Alternatively, a
plurality of combinations of the charging current, the
cut-off current, and the cut-off voltage may be set as
the charging condition.
[0075]
In this embodiment, the case where the secondary
battery is the lithium-ion battery has been assumed.
However, the present technology can also be applied to
a case where other types of secondary batteries having
a property that increases the deterioration speed in an
environment at a temperature lower than a certain
temperature such as a room temperature are assumed.
[0076]
In the above-mentioned embodiment, it is assumed
that the OCV capacity is adopted as the deterioration
index of the secondary battery. However, the present
technology is not limited thereto and it is possible to
adopt other various indexes.
LOO771 For example, it is possible to indicate the
resistance value of the secondary battery. When the
secondary battery is deteriorated, the resistance value
gradually increases. In view of this, the charging
control unit 26 compares a resistance value R(t,) of the
secondary battery at the point of time of the total
operating time t, with an allowable resistance value
RRef(tn)o f the secondary battery at the point of time of
the total operating time t,.
If R (t,)
In the above-mentioned embodiment, the table
showing the correspondence between the combination of
the temperature of the secondary battery with the
internal resistance and the charging condition is used
as a charging condition table. However, a table of a
correspondence between the temperature or the internal
resistance and the charging condition may be adopted.
Alternatively, a table showing a correspondence between
one or more kinds of parameters and a charging
condition may be used.
[00821 Note that, the present technology may also
take the following configurations.
(1) A power storage system, including:
a parameter detector that detects a parameter of a
secondary battery;
a table storage unit that stores a table
indicating a correspondence between a parameter of the
secondary battery and a charging condition; and
a charging control unit configured to refer to,
based on the detected parameter, a corresponding
charging condition from the table and make control to
charge the secondary battery in this charging
condition.
[0083] (2). The power storage system according to (I),
5 in which
the table is a table showing a correspondence
between a combination of the temperature of the
secondary battery with an internal resistance and a
charging condition, and
the parameter detector is configured detect the
temperature of the secondary battery and the internal
resistance.
[0084] (3) The power storage system according to (1)
or (2), in which
the charging condition is defined to ensure a
predetermined use period of the secondary battery.
[0085] (4) The power storage system according to any
one of (1) to ( 3 ) , in which
the charging control unit is configured to refer
20 - to ehe corresponding charging condition from the table
and perform charging in this charging condition if the
detected temperature is lower than a predetermined
temperature, and to perform charging in a fixed
charging condition if the detected temperature is equal
to or higher than the predetermined temperature.
[0086] (5) The power storage system according to any
one of (1) to ( 4 ) , further including:
an amount-of-deterioration calculator that
calculates an amount of deterioration of the secondary
battery; and
an allowable amount-of-deterioration calculator
that calculates an allowable amount of deterioration of
the secondary battery, in which
the charging control unit is configured to compare
the calculated amount of deterioration with the
calculated allowable amount of deterioration and to
update the charging condition of the table such that
the deterioration speed of the secondary battery is
suppressed according to a result thereof.
[0087] (6) The power storage system according to ( 5 ) ,
in which
the amount-of-deterioration calculator and the
allowable amount-of-deterioration calculator calculate
the amount of deterioration and the allowable amount of
deterioration, respectively, according to a
predetermined timing condition, and
the charging control unit is configured to update,
ifa change value of the amount of deterioration that
is next acquired with respect to the amount of
deterioration at a point of time at which the charging
condition of the table was updated is larger than a
change value of the allowable amount of deterioration
that is next acquired with respect to the allowable
amount of deterioration at the point of time at which
the charging condition of the table was updated, the
charging condition of the table such that a
deterioration speed of the secondary battery is reduced.
Description of Reference Numerals
[0088]
1 secondary battery module
2 charging control apparatus
3 charging unit
10 deterioration parameter detector
11 current monitoring unit
12 voltage monitoring unit
13 time monitoring unit
14 temperature monitoring unit
21 use history storage unit
22 deterioration index calculator
23 allowable deterioration index calculator
24 resistance calculator
25 charging condition table storage unit
26 charging control unit
100 power storage system

Claims
[I] A power storage system, comprising:
a parameter detector that detects a parameter of a
secondary battery;
5 a table storage unit that stores a table
indicating a correspondence between a parameter of the
secondary battery and a charging condition; and
a charging control unit configured to refer to,
based on the detected parameter, a corresponding
charging condition from the table and make control to
charge the secondary battery in this charging
condition.
[2] The power storage system according to claim 1,
wherein
the table is a table showing a correspondence
between a combination of the temperature of the
secondary battery with an internal resistance and a
charging condition.
[ 3 ] The power storage system according to claim 2,
20 . wherein *-
the charging condition is defined to ensure a
predetermined use period of the secondary battery.
[ 4 ] The power storage system according to claim 3,
wherein
the charging control unit is configured to refer
to the corresponding charging condition from the table
and perform charging in this charging condition if the
detected temperature is lower than a predetermined
temperature, and to perform charging in a fixed
charging condition if the detected temperature is equal
5 to or higher than the predetermined temperature.
[5] The power storage system according to claim 4,
further comprising:
an amount-of-deterioration calculator that
calculates an amount of deterioration of the secondary
10 battery; and
an allowable amount-of-deterioration calculator
that calculates an allowable amount of deterioration of
the secondary battery, wherein
the charging control unit is configured to compare
15 the calculated amount of deterioration with the
calculated allowable amount of deterioration and to
update the charging condition of the table such that
the deterioration speed of the secondary battery is
suppressed according to a result thereof.
(61 ,,?he power storage system according to claim 5,
wherein
the amount-of-deterioration calculator and the
allowable amount-of-deterioration calculator calculate
the amount of deterioration and the allowable amount of
deterioration, respectively, according to a
predetermined timing condition, and
the charging control unit is configured to upci'ate,
if a change value of the amount of deterioration that
is next acquired with respect to the amount of
dhterioration at'a point of time at which the charging
5 condition of the table was updated is larger than a
change value of the allowable amount of deterioration
that is next acquired with respect to the allowable
amount of deterioration at the point of time at which
the charging condition of the table was updated, the
10 charging condition of the table such that a
deterioration speed of the secondary battery is reduced.
[ 7 ] A charging method for a secondary battery,
cgmprising:
detecting a parameter of the secondary battery;
15 referring to a corr&sponding charging condition
from a table showing a correspondence between the
parameter of the secondary battery and the charging
condition based on the detected parameter; and
charging the secondary battery in this charging
+ ,
2 0 condition