DESCRIPTION
POWER STORAGE DEVICE ANDMETHOD OF CONTROLLING POWER STORAGE
DEVICE
5 TECHNICAL FIELD
[OOOl]
The present disclosure r e l a t e s t o a power storage
device and a method of controlling the porier storage device.
10 BACKGROUND ART
[0002]
In a known power storage apparatus, power storage
modules are connected, and a common control device (also
calledthemaincontrollerwhereappropriate) i s p r o v i d e d f o r
15 theporier storagemodules. Eachoftheporier storagemodules
has a module c o n t r o l l e r , and communication is performed
between the module c o n t r o l l e r and t h e main c o n t r o l l e r via a
communication channel.
[0003]
2 0 So as t o monitor the condition of a power storage unit
and d e t e c t malfunction, the module c o n t r o l l e r includes a
monitoring c i r c u i t and a microcomputer (also c a l l e d the sub
micro-controllerunitwhereappropriate). Thepower storage
u n i t is formedwith series-connectedsubmodules, for example.
25 The monitoring c i r c u i t monitors the voltages of the
respective sub modules, compares the voltages of the
respective sub modules with a predetermined threshold value
using a comparator, and outputs detection signals (1-bit
detection signals, f o r example) i n d i c a t i n g
30 normality/abnormality.
[0004]
A t a time of charging, the voltage of each sub module
is comparedwithapredeterminedvalue, a n d a d e t e c t i o n s i g n a l
indicating whether the voltage is an overvoltage (also
r e f e r r e d t o a s OVwhere appropriate) is generated. A t a t i m e
5 of discharging, the voltage of each sub module is compared
withapredeterminedvalue, a n d a d e t e c t i o n s i g n a l indicating
whether the voltage is an undervoltage ( a l s o r e f e r r e d t o as
UV where appropriate) is generated. A t a t i m e of
charging/discharging, t h e v a l u e o f t h e current flowing i n t h e
10 sub modules is compared with a predetermined value, and a
d e t e c t i o n s i g n a l i n d i c a t i n g whether the current is an
overcurrent ( a l s o r e f e r r e d t o as OC where appropriate) is
generated. Further, a t a time of charging/discharging, the
temperature of each sub module is compared with a
15 predetermined value, and a detection s i g n a l i n d i c a t i n g
whether the temperature is an overtemperature ( a l s o r e f e r r e d
t o as OT where appropriate) is generated.
[0005]
Further, when a power storage module is charged, the
20 voltages and the currents of the respective sub modules are
s u p p l i e d t o t h e submicro-controller unit of eachmodule, and
balance adjustment is performed t o equalize the voltages of
t h e submodules. Without thebalance adjustment, some o f t h e
submoduleswill n o t be s u f f i c i e n t l y chargeddueto v a r i a t i o n
25 among the sub modules.
[0006]
For the balance adjustment, the above described
detection signals from the monitoring c i r c u i t are supplied
t o the sub micro-controller u n i t . Further, the detection
30 s i g n a l s a r e t r a n s f e r r e d from the module c o n t r o l l e r to the
microcomputer (also c a l l e d t h e main micro-controller u n i t
where appropriate) o f t h e m a i n c o n t r o l l e r v i a a communication
channel. The main c o n t r o l l e r receives d e t e c t i o n s i g n a l s
from the respective power storage modules, and controls
charging/discharging operations.
5 [0007]
For example, according t o Patent Document 1 mentioned
below, w h e n t h e r e i s a submodulethat has a v o l t a g e d i f f e r e n c e
from the highest voltage detected from sub modules ( c e l l
blocks) within a discharging voltage range, charging is
10 temporarily stopped, and the sub module as well as the sub
module having t h e highest voltage is made t o discharge, t o
update the highest voltage a f t e r the discharging. The c e l l
balance adjustment is repeated u n t i l the voltage difference
between the h i g h e s t voltage and the lowest voltage f a l l s
15 within a predetermined voltage range, so t h a t the time
required for c e l l b a l a n c e control canbe shortened, according
t o Patent Document 1.
CITATION LIST
20 PATENT DOCUMENT
[00081
Patent Document 1: Japanese Patent Application
Laid-Open No. 2012-60691
25 SUMMARY OF THE INVENTION
PROBLEMS TO BE SOLVED BY THE INVENTION
[0009]
According t o Patent Document 1, charging is repeatedly
enabled and disabled. Therefore, i f there are differences
30 i n c h a r a c t e r i s t i c s among the sub modules, the time required
f o r reachinga fullychargedstatebecomes considerablylong,
and noise is generated as the charging is repeatedly enabled
and disabled.
[OOlO]
Therefore, the present disclosure aims t o provide a
5 power storage device t h a t can complete charging i n a short
time and prevent generation of noise, and a method of
c o n t r o l l i n g the power storage device.
SOLUTIONS TO PROBLEMS
10 [ O O l l ]
The present disclosure is a power storage device t h a t
includes :
power storage u n i t s e a c h i n c l u d i n g a t l e a s t o n e b a t t e r y ,
t h e power storage u n i t s being connected i n s e r i e s ;
15 c e l l balance u n i t s connected i n p a r a l l e l t o the
respective power storage u n i t s via switches; and
a c o n t r o l u n i t t h a t p e r f o r m s controltochargetheporier
storage u n i t s with a f i r s t constant current value, and, when
t h e power storage unit having the highest voltage among the
20 power storage units reaches a f i r s t p o t e n t i a l , connect the
corresponding one of the c e l l balance u n i t s t o the power
s t o r a g e u n i t having the highest voltage, and switch the
charging current t o a second constant current value t h a t is
smaller than the f i r s t constant c u r r e n t value.
25
EFFECTS OF THE INVENTION
[00121
According t o the p r e s e n t d i s c l o s u r e , the time required
f o r completing charging can be shortened, and generation
30 noise can be prevented. It should be noted t h a t the e f f e c t s
t o be achieved are not limited t o t h e e f f e c t described above,
and may include any of the effects described in the present
disclosure.
BRIEF DESCRIPTION OF DRAWINGS
5 [0013]
Fig. 1 is a block diagram of an example of a power storage
apparatus.
Fig. 2 is a schematic diagram showing an example of the
external appearance of a power storage apparatus being used.
10 Fig. 3isablockdiagramshowingthe relationshipamong
controllers in a power storage apparatus.
Fig. 4 is a block diagram showing a first embodiment
of the control unit of a power storage module according to
the present disclosure.
15 Fig. 5 is a connection diagram of a cell balance
discharging circuit according tothe first embodiment of the
present disclosure.
Fig. 6 is a flowchart showing the flow of a control
process according to the first embodiment of the present
20 disclosure.
Fig. 7 is a flowchart showing the flow of the control
process according to the first embodiment of the present
disclosure.
Fig. 8 shows graphs for explaining a first example of
25 control according to the first embodiment of the present
disclosure.
Fig. 9 shows graphs for explaining a second example of
control according to the first embodiment of the present
disclosure.
30 Fig. 10 shows graphs for explaining the second example
of control according to the first embodiment of the present
disclosure.
Fig. 11 shows graphs for explaining a modification of
control according to the first embodiment of the present
disclosure.
5 Fig. 12 is a connection diagram of a cell balance
discharging circuit according to a second embodiment of the
present disclosure.
Fig. 13 is a flowchart showing the flow of a control
process according to the second embodiment of the present
10 disclosure.
Fig. 14 is a flowchart showing the flow of the control
process according to the second embodiment of the present
disclosure.
Fig. 15 shows graphs for explaining an example of
15 control according to the second embodiment of the present
disclosure.
Fig. 16 shows graphs for explaining the example of
control according to the second embodiment of the present
disclosure.
2 0 Fig. 17isablockdiagramofafirstexampleapplication
of the present disclosure.
Fig. 18 is a block diagram of a second example
application of the present disclosure.
25 MODES FOR CARRYING OUT THE INVENTION
[0014]
The embodiments describedbelorvarepreferred specific
examples of the present disclosure, and various preferred
technical restrictions are put thereon. However, the scope
30 ofthepresentdisclosureisnotlimitedbythoseembodiments,
unless otherwise specified in the described below.
The present disclosure w i l l be explained i n the
following order.
<1. F i r s t Embodiment of the Present Disclosure>
12. Second Embodiment of the Present Disclosure>
<3. Applications>
<4. Modifications>
[00151
<1. F i r s t Embodiment of the Present Disclosure:
[Power Storage Apparatus]
10 Where a large number of power storage elements such as
b a t t e r y c e l l s are usedforgeneratinghighpower, a s t r u c t u r e
inr$hichpowerstorageunits ( h e r e i n a f t e r r e f e r r e d t o a s p o w e r
storage modules) a r e connected, and a control device is
provided f o r t h e power storage modules is employed. Such a
15 s t r u c t u r e is called a power storage apparatus. Further, it
is possible t o form a power storage system i n which power
storage apparatuses a r e connected. Other than b a t t e r y c e l l s ,
c a p a c i t o r s may be used a s t h e power storage elements.
[0016]
2 0 A power storage module is a unit formed with a
combination of a power storage unit including
series-connectedbattery c e l l s suchas l i t h i u m i o n secondary
cells or series-connected sub modules each consisting of
parallel-connected b a t t e r y cells, and a module c o n t r o l l e r
25 provided for each module. The sub micro-controller unit of
each module c o n t r o l l e r is connected t o the main
micro-controller unit of the main c o n t r o l l e r t h a t is the
overallcontroldeviceviaadatatransmissionchannel ( a b u s ) ,
andthemainmicro-controllerunitperformschargemanagement,
30 discharge management, and management of degradation control
and the l i k e .
[0017]
A s e r i a l i n t e r f a c e is used as the bus. S p e c i f i c a l l y ,
a n I n t e r - I n t e g r a t e d C i r c u i t (I2C) method, aSystemManagement
(SM) bus, aControllerAreaNetwork (CAN), a S e r i a l P e r i p h e r a 1
5 I n t e r f a c e (SPI) , or the l i k e is used as t h e s e r i a l i n t e r f a c e .
[0018]
Communication according t o the 12C method is used, for
example. This method is designed f o r performing s e r i a l
communication with a d i r e c t l y connected device located a t a
10 r e l a t i v e l y short distance. Onemaster andone ormore slaves
a r e connected by two l i n e s . With the standard being the
crosstalktransmittedthrough one o f t h e l i n e s , data signals
a r e t r a n s f e r r e d through the other one of the l i n e s . Each of
the slaves has an address included i n data;and data is
15 t r a n s f e r r e d w h i l e acknowledge is returned fromthe receiving
side f o r each byte so as t o confirm each other. In the case
of the power storage apparatus, the main micro-controller
unit serves as themaster, and the submicro-controller units
serve as the slaves.
20 [00191
Data is transmitted fromthe submicro-controller unit
of eachmodule
For example, information about the i n t e r n a l s t a t e of each
power storage module, or b a t t e r y information such as
25 information about the voltages o f the respective battery
c e l l s and the voltage o f t h e entiremodule, information about
current, and information about temperature is transmitted
from the sub micro-controller u n i t t o t h e main
micro-controller u n i t , so t h a t t h e charging process and the
30 dischargingprocess foreachpower storagemoduleismanaged.
[00201
Fig. 1 shows a s p e c i f i c example of the connection
s t r u c t u r e inthepower s t o r a g e apparatus. Fourpower storage
modulesMODlthroughMOD4 a r e c o n n e c t e d i n s e r i e s , forexample.
In t h i s case, the output voltage of the e n t i r e power storage
5 apparatus, such as approximately 200 V, is applied t o a
p o s i t i v e terminal 1 (VB+) and a negative terminal 2 (VB-),
f o r example. The power storage modules MODl through MOD4,
respectively, include module c o n t r o l l e r s CNTl through CNT4,
and power storage units BB1 through BB4 in which
10 parallel-connectedbatterycellsorsubmodulesareconnected.
The power storage u n i t s BBI through BB4 are connected via a
power supply l i n e .
[0021]
Each of the module c o n t r o l l e r s includes a monitoring
15 c i r c u i t and a sub control u n i t , as w i l l be described l a t e r .
The main c o n t r o l l e r ICNT and the module c o n t r o l l e r s CNTl
through CNT4 are connectedvia a common s e r i a l communication
bus 3 . Battery information such as the voltages o f the
respective modules is transmitted fromthe respectivemodule
20 c o n t r o l l e r s tothemain c o n t r o l l e r ICNT. Themain c o n t r o l l e r
ICNT f u r t h e r includes a communication terminal 4 so t h a t
communication with the outside such as an e l e c t r o n i c control
u n i t can be performed.
100221
2 5 As shown i n Fig. 2, two power storage modules MOD1 and
MOD2, a n d t h e m a i n c o n t r o l l e r ICNTeachhas abox-like casing,
and a r e stacked f o r use, for example. As an option, an
Uninterruptable Power Supply (UPS) 5 is used i n some cases.
As indicated by a dashed l i n e i n Fig. 2, the main c o n t r o l l e r
30 ICNT and the module c o n t r o l l e r s CNT of the respective power
storage modules are connected by the bus 3
[0023]
Further, i n an embodiment of the present disclosure,
as shown i n Fig. 3 , the sub control u n i t s (denoted by SUB MCU
i n the drawing) of respective power storage modules are
5 connectedtomainmicro-controllerunits (denotedbyMAINMCU
i n the drawing) so t h a t the power storage modules are
controlled. Further, t h e main micro-controller u n i t s are
connected t o an e l e c t r o n i c control unit (denoted by ECU i n
thedrawing) o f t h e h i g h e s t o r d e r . ' A n e l e c t r o n i c c o n t r o l u n i t
10 is normally a unit t h a t controls analog devices.
[00241
[Example of a Module Controller and a Main Controller]
Referringnotito Fig. 4, anexamplestructureofamodule
c o n t r o l l e r CNT and a main c o n t r o l l e r ICNT is described. A
15 power storage unit BB is formed with n (16, f o r example)
b a t t e r y cells ( h e r e i n a f t e r referred t o simply as c e l l s where
appropriate) C 1 t h r o u g h C 1 6 t h a t a r e c o n n e c t e d i n s e r i e s . The
power storage unit BB may be formed with parallel-connected
c e l l s (sub modules) t h a t a r e connected i n series. The
20 voltages of the respective cells are supplied t o a c e l l
voltage multiplexer 11, and the voltages of the c e l l s C1
through C16 a r e sequentially selected and supplied t o an A/D
converter and comparator 12. Further, a c e l l balance
discharging c i r c u i t 23 f o r causing the respective c e l l s C1
25 t h r o u g h C 1 6 t o d i s c h a r g e i n c e l l b a l a n c e c o n t r o l i s p r o v i d e d .
[0025]
The voltages of the 16 c e l l s are subjected t o
time-division multiplexing by the c e l l voltage multiplexer
11, and are converted i n t o d i g i t a l s i g n a l s and are f u r t h e r
30 compared with a voltage threshold by the A/D converter and
comparator 12. The A/D converter and comparator 12 outputs
14- to 18-bit digital voltage data of the respective cells,
and results (1-bit signals, for example) of the comparison
between the voltages ofthe respective cells and the voltage
threshold. The signals output from the A/D converter and
5 comparator 12 are supplied to a monitoring circuit 13.
100261
Further, a temperature measuring unit 14 that measures
temperatures of the respective cells, and a temperature
measuring unit 15 that measures temperature in the IC are
10 provided. Temperature information from the temperature
measuring units 14 and 15 is supplied to a temperature
multiplexer 16. Temperature data multiplexed by the
temperature multiplexer 16 is supplied to the A/D converter
and comparator 12. The A/D converter and comparator 12
15 generates digital temperature data, and outputs results
(1-bit signals, for example) of comparison between the
digital temperature data and a temperature threshold. As
described above, the A/D converter and comparator 12 also
outputs results of comparison with respect to cell voltage
20 data. Therefore, another A/D converter and comparator for
temperature may also be provided.
[0027]
A resistor 17 that detects the currents flowing in the
power storage unit (the cells C1 through C16) is connected
25 in series to the power storage unit BB. The voltages at both
ends of the resistor 17 are supplied to an A/D converter and
comparator 19 via an amplifier 18. The A/D converter and
comparator19 outputs digital current data and results (1-bit
signals, for example) of comparison between current values
30 and a current threshold. The signals output from the A/D
converter and comparator 19 are supplied to the monitoring
circuit 13.
[0028]
Some of the 1-bit signals that are output from the A/D
converter andcomparator12 are detection signals indicating
5 normality/abnormalityofthevoltagesoftherespectivecells.
At a time of charging, the voltage of each cell is compared
withapredeterminedvalue, anda detection signal indicating
whether the voltage is an overvoltage OV is generated. At
a time of discharging, the voltage of each cell is compared
10 with apredeterminedvalue, andadetection signal indicating
whether the voltage is an undervoltage UV is generated. The
other 1-bit signals that are output from the A/D converter
and comparator 12 are detection signals indicating an
overtemperature OT. The 1-bit signals that are output from
15 the A/D converter and comparator 19 are detection signals
indicating an overcurrent OC.
[0029]
The above described detection signals, voltage value
data, current value data, and temperature data are supplied
20 frornthernonitoringcircuit13to a submicro-controller unit
20. The monitoring circuit 13 and the sub micro-controller
unit 20 are connected by serial communication, for example.
Using the received detection signals, the sub
m i c r o - c o n t r o l l e r u n i t 2 0 p e r f o r m s adiagnosingprocess onthe
25 module controller CNT as necessary. The detection signals
and data indicating results of the diagnosing process are
output and supplied from the sub micro-controller unit 20 to
a communication unit 21.
[00301
30 The communication unit 21 is the interface for
conducting serial communication such as 12C communication
with the main micro-controller unit of the main controller
ICNT via the bus 3. The communication method herein can use
a wired or wireless communication channel. Although not
shownin Fig. 4, the submicro-controller units ofthemodule
5 controllers ofthe other power storage modules are connected
to the bus 3.
[0031]
A positive terminal 22a and a negative terminal 22b of
the power storage module MOD are connected to a positive
10 terminal 32a and a negative terminal 32b of the main
controller ICNT, respectively, via power supply lines.
[0032]
A communication unit 31 of the main controller ICNT is
connected to the bus 3. A main micro-controller unit 30 is
15 connected to the communication unit 31, and communication
being conducted through the communication unit 31 is
controlled by the main micro-controller unit 30. Further,
the main micro-controller unit 30 is connected to an
electronic control unit ECU of the higher order via a
20 communication channel.
[0033]
A power supply voltage generated by a regulator 33 is
supplied to the main micro-controller unit 30. The main
controller ICNT includes apositive terminal1 andanegative
25 terminal2. In the power supplyoutput path, switching units
34 and 35 are inserted in series. These switching units 34
and 35 are controlled by the main micro-controller unit 30.
The switching units 34 and 35 each include a switch element
(such as a Field Effect Transistor (FET) or an Insulated Gate
30 Bipolar Transistor (IGBT) ) , andadiode connectedin parallel
to the switch element.
[0034]
When charging is prohibited, the switching unit 34 is
switchedoff. Whendischargingisprohibited, the switching
unit 35 is switched o f f . Further, when neither charging nor
5 discharging is performed, the respective switch elements of
the switching u n i t s 34 and 35 a r e sriitched o f f . The main
micro-controllerunit 3 0 t r a n s m i t s t h e d a t a receivedfromthe
power storage module MOD t o the e l e c t r o n i c c o n t r o l u n i t ECU
o f t h e h i g h e r order. Further, themainmicro-controllerunit
10 30 receives a c o n t r o l s i g n a l r e l ~ a t e d t oc harging/discharging
from the e l e c t r o n i c control unit ECU.
[0035]
[Cell Balance Discharging C i r c u i t ]
Fig. 5 shows anexample o f t h e c e l l b a l a n c e discharging
15 c i r c u i t 23. A r e s i s t o r rl and a switch sl are connected i n
p a r a l l e l t o the c e l l C1. Likewise, r e s i s t o r s r2 through r16
and switches s2 through s16 a r e connected in p a r a l l e l t o the
c e l l s C2 through C16, respectively. The switches sl through
s16 a r e formed with semiconductor switch elements such as
20 FETs.
[0036]
The switching on and off of the switches sl through s16
is controlled by a switching control signal generated by the
s u b m i c r o - c o n t r o l l e r u n i t 2 0 , for example. Whentheswitches
25 sl through s16 are switched on, the p o s i t i v e electrodes and
the negative electrodes of the cells C1 through C16 a r e
connected via the r e s i s t o r s rl through r16, and t h e charges
a c c u m u l a t e d i n t h e c e l l s C l t h r o u g h C 1 6 a r e d i s c h a r g e d . While
a charging current is being supplied t o the c e l l s C1 through
30 C16, when the switches sl through s16 are switched on, the
charging current is divided, and the s u b s t a n t i a l charging
current decreases. For example, during a charging period,
a switch t h a t has been switched on maintains the on-state.
[OD371
A charging c i r c u i t is connected t o the p o s i t i v e
5 terminal 1 and the negative terminal 2, t o charge the c e l l s
ClthroughC16. Chargingisperformedwithaconstantcurrent.
In the p r e s e n t d i s c l o s u r e , the charging current is gradually
lowered. That is, the voltages of the respective c e l l s are
monitoredbythemonitoring c i r c u i t 13 a t a time of charging.
10 When the voltage of one of the c e l l s reaches a predetermined
c u r r e n t s w i t c h i n g v o l t a g e V 1 , t h e c u r r e n t i s l o r ~ e r e d o n e l e v e l ,
and the switch (the c e l l balance discharging c i r c u i t 23)
corresponding t o the c e l l h a v i n g t h e voltage t h a t has reached
the current switching voltage V1 is switched on. In t h i s
15 manner, increase i n voltage is r e s t r a i n e d . This operation
is repeated, and, when a predetermined t o t a l voltage or the
voltages of a l m o s t a l l t h e c e l l s reach a charging completion
voltage.Vf, the charging is stopped.
100381
[Control Operation]
Referring now t o the flowcharts i n Figs. 6 and 7, the
c o n t r o l process t o be performed by the sub micro-controller
u n i t 20 a t a time of charging is described. Figs. 6 and 7
show the flow of a single process, but the process is divided
25 and shown in the two flowcharts due t o l i m i t a t i o n s of space.
The d e f i n i t i o n s of the symbols used i n the description below
a r e a s follows.
[00391
V c e l l n: the nth c e l l
Vcellmin: the lowest voltage among n c e l l s
Vov: charging suspension voltage
Vf: charging completion voltage
Vcellov: the voltage of a cell that has reached the
charging suspension voltage among the n cells
VL: discharging voltage
5 VlthroughVn: currentswitchingvoltages (discharging
resistor on-voltages) (V1 < V2 < V3 ... < Vn)
cellVn: a cell that has reached Vn
[0040]
For example, Vov is higher than Vf, Vov is set at 4.15
10 V, and Vf is set at 4.10 V. A voltage such as equal to or
higher than 4.2 V, which is higher than Vov, is regarded as
an overcharging voltage, and charging is prohibited.
Further, thedischargingvoltageVLis setat3.0V. Avoltage
such as 2.3 V, which is lower than VL, is regarded as an
15 overdischarging voltage, and discharging is prohibited. In
reality, each voltage is allowed to have a margin of error.
In the present disclosure, the secondarycellsto be usedare
lithium ion secondary cells containing a positive-terminal
active material, and a carbon material such as graphite as
20 a negative-terminal active material, for example. The
positivematerial is not particularly limited, but amaterial
containing a positive-terminal active material having an
olivine structure can be used. In a battery of this type,
Vov is set at 3.55 V, and VL is set at 2.0 V, for example.
25 [0041]
Step S 1 : Charging is started.
Step 52: A check is made to determine whether Vcell n
is higher than VL. A check is made to determine whether the
voltages of all the cells are higher than VL.
30 Step S3: If the result of the determination in step 52
is negative, preliminary charging is performed. In the
preliminary charging, the charging current is set a t 1 A, f o r
example. The preliminary charging is continued u n t i l the
r e s u l t of the determination in step 52 turns p o s i t i v e .
[0042]
5 Step S4: I f the r e s u l t of the determination i n step S2
is positive, a check is made t o determine whether Vcellmin
is equal to or higher than Vf.
Step S5: I f the r e s u l t of the determination i n step S4
is positive, the charging is completed.
10 Step S6: I f the r e s u l t of the determination i n step S4
is negative, a check is made t o determine whether V c e l l n is
equal t o or higher than Vov. I f the r e s u l t of the
determination i n step S6 is positive, the process moves on
t o step S16 (Fig. 7 ) .
15 100431
Step S7: Normal charging is performed. For example,
1-C charging is performed. The 1-C charging involves a
currentvaluewithwhichratedchargingforanominalcapacity
b a t t e r y is completed i n one hour (1 h) . For example, i n the
20 case of a lithium ion secondary c e l l with a nominal capacity
of 2.0 Ah, 1 C = 2.0 Ah/l h = 2.0 A.
Step S8: A check is made t o determine whether Vcell n
is equal t o or higher than V 1 . For example, the i n i t i a l
current switching voltage is s e t a t V1 = 4.05 V. I f t h i s
25 condition is not s a t i s f i e d , the process returns t o step 57.
StepS9: The cellbalancingisenabledonlyforthecell
t h a t has reached the current switching voltage V1. That is,
i n the c e l l balance discharging c i r c u i t 23, the switch of the
corresponding c e l l is switched on. Even i f the c e l l having
30 t h e cell balancing enabled reaches the current switching
voltage Vn t h e r e a f t e r , any special process w i l l not be
performed for the c e l l .
[00441
Step SlO : The charging current is switched t o a smaller
value. For example, the charging current s t a r t s a t 1 C, and
5 is then switched to 0.7 C. Further, every time the minimum
voltage of the c e l l reaches a current switching voltage, the
charging current is switched t o 0.4 C, and then t o 0.1 C.
Step S l l : The charging with 0.7 C is continued.
[0045]
10 Step S12: The same determination processes as those i n
s t e p S4 and step S6 are performed. That is, a check is made
t o determine whether Vcellmin is equal t o or higher than Vf.
It the r e s u l t is positive, the charging is completed ( s t e p
S5). A check is made t o determine whether V c e l l n is equal
15 t o o r h i g h e r t h a n v o v . I f the r e s u l t is positive, the process
moves on t o step 515 (Fig. 7 ) . In step S15, the charging is
temporarily stopped. I f any of these conditions is not
s a t i s f i e d , the process moves on t o step 513.
100461
2 0 StepS13:Acheckismadetodeterminewhetheravoltage
other than Vcell V1 is equal t o or higher than V,+I (such as
V2) . I f t h i s condition is not s a t i s f i e d , the process r e t u r n s
t o s t e p S11 (the charging continues).
Step S14: The c e l l balancing is enabled only f o r the
25 cell t h a t has reached V,+I. That i s , i n the cell balance
discharging c i r c u i t 23, the switch of the corresponding c e l l
is switched on. Even i f the cell having the c e l l balancing
enabled reaches a current switching voltage t h e r e a f t e r , any
s p e c i a l process w i l l not be performed f o r the c e l l . After
30 s t e p 514, the process moves on t o step S10. In step S10, the
charging current is f u r t h e r reduced. For example, the
charging current is reduced from 0.7 C to 0.4 C.
[0047]
Step S16: If the result of the determination in step
S6 is positive, or if Vcell n is equal to or higher than Vov,
5 the cell balancing is enabled only for cellov having the
voltage equal to or higher than Vov.
Step S17: A check is made to determine whether Vcellov
is equal to or lower than Vn. If this condition is not
satisfied, theprocessreturnstostepS16 (thecellbalancing
10 is enabled only for cellov).
Step S18: If the condition in step S18 is satisfied,
only the cell balancing that was on prior to the charging
suspension process is enabled. The process then returns to
step S11 (the charging continues) in Fig. 6.
15 LO0481
[First Example of Control According to the First
Embodiment]
Referring to the graphs showing temporal changes in
cell voltages in Fig. 8, a first example of control is
20 described. The power storage unit BB is formed with four
cells C1 through C4. Due to the differences in
characteristics among the cells, the temporal change graphs
differ from one another. First, the voltages of the cells
C1 through C4 gradually become higher with 1-C charging.
25 [0049]
When the voltage of the cell C2 reaches the current
switching voltage V1 (4.05 V, for example) at time tl, the
switch s2 of the cell balance discharging circuit 23 is
switched on, and the charging.current is reduced to 0.7 C
30 (steps SB, S9, and S10 in Fig. 6 ) . The charging is then
continued (step S11). As the charging current is reduced,
t h e v o l t a g e r i s e curvebecomes g e n t l e r a f t e r t i m e t l . Before
time tl, the voltage r i s e curves of the respective c e l l s run
p a r a l l e l t o one another. Since the switch s2 is switched on
a t t i m e tl, the voltage r i s e curve of the c e l l C2 becomes
g e n t l e r than those of the other c e l l s .
[O050]
A t t i m e t2, a c e l l other than the c e l l C2, or the c e l l
C1, f o r example, reaches the current switching voltage V2.
Therefore, the switch sl of the c e l l balance discharging
c i r c u i t 2 3 i s sriitchedon, andthe c h a r g i n g c u r r e n t i s reduced
t o 0.4 C. As the charging current is reduced, the voltage
r i s e curve becomes gentler a f t e r t i m e t 2 . A f t e r t i m e t 2 , t h e
voltage r i s e curve of the c e l l C1 also becomes gentler than
those of the other c e l l s C3 and C4.
[0051]
The charging is f u r t h e r continued, and the voltage o f
the cell C3 reaches the voltage Vf a t time t 3 . Therefore,
the switch s3 of the c e l l balance discharging c i r c u i t 23 is
switched on, and the charging current is reduced t o 0 . 1 C.
After t i m e t3, the voltage rise curve of the cell C3 a l s o
becomes g e n t l e r than t h a t of the other c e l l C4.
[O052]
The charging is f u r t h e r continued, and the voltage o f
the c e l l C4 reaches the voltage Vf a t t i m e t 4 . As the lowest
voltage reaches the voltage V f , the charging is completed
( s t e p s 512 and 55 i n Fig. 6 ) . In t h i s manner, charging can
be performed u n t i l the voltages of c e l l s reach the charging
completion voltage Vf.
[0053]
In the above described f i r s t embodiment o f t h e present
d i s c l o s u r e , generation of a spike-like (whisker-like)
voltage accompanying the switching on and off the charging
current can be prevented. Furthermore, in the first
embodiment of the present disclosure, the charging current
for each cell with a high voltage is made smaller, so that
5 the charging current can be reduced.
[0054]
[Second Example of Control According to the First
Embodiment]
Referring to the graphs showing temporal changes in
10 cell voltages in Figs. 9 and 10, a second example of control
is described. Figs. 9 and 10 show one set of graphs showing
temporally continuous changes, but the changes are divided
and shown in the two drawings due to limitations of space.
In this example, the power storage unit BB is formed with
15 series-connected four cells C1 through C4, as in the above
described first example. In the second example, the
differences among the cells are significantly larger than
those in the first example. First, the voltages of the cells
Cl through C4 gradually become higher with 1-C charging.
20 [0055]
When the voltage of the cell C2 reaches the current
switching voltage V1 (4.05 V, for example) at time tl, the
switch s2 of the cell balance discharging circuit 23 is
sv~itched on, and the charging current is reduced to 0.7 C
25 (steps S8, S9, and S10 in Fig. 6). The charging is then
continued (step S11). As the charging current is reduced,
thevoltage rise curvebecomesgentleraftertimetl. Before
time tl, the voltage rise curves of the respective cells run
parallel to one another. Since the switch s2 is switched on
30 at time tl, the voltage rise curve of the cell C2 becomes
gentler than those of the other cells.
[00561
A t time t 2 , a c e l l other than the c e l l C2, or the c e l l
C1, f o r example, reaches the current switching voltage V2.
Therefore, the switch sl of the c e l l balance discharging
5 c i r c u i t 2 3 is switchedon, andthe c h a r g i n g c u r r e n t i s reduced
t o 0.4 C. A s the charging current is reduced, the voltage
r i s e curve becomes even gentler a f t e r time t 2 . After time
t2, thevoltage r i s e c u r v e o f t h e cellC1alsobecomes gentler
than those of the other c e l l s C3 and C4.
10 to0571
A t t i m e t3, a c e l l other than the c e l l s C1 and C2, or
the c e l l C3, for example, reaches the current switching
voltage Vn. Therefore, the switch s3 of the c e l l balance
discharging c i r c u i t 23 is switched on, and the charging
15 current is reduced t o 0.1 C. As the charging current is
reduced, the voltage r i s e curve becomes even g e n t l e r a f t e r
t i m e t 3 . After time t 3 , t h e voltage rise curve of the cell
C3 a l s o becomes g e n t l e r than t h a t of the other cell C4.
[00581
20 After time t3, the voltage r i s e curves of the c e l l s C1
through C3 have the same i n c l i n a t i o n s , but the i n c l i n a t i o n
of the voltage rise curve of the c e l l C4 is higher than those
of the cells C1 through C3. A t t i m e t 4 , the voltage of the
c e l l C2 reaches the charging suspension voltage Vov. As a
25 r e s u l t o f t h e d e t e r m i n a t i o n i n step S12in Fig. 6, theprocess
moves o n t o step S15 (Fig. 7 ) , andthechargingistemporarily
stopped. As the c e l l balancing is enabled only for the c e l l
C2, the voltage of t h e cell C2 becomes lower. A t time t5,
the charging is resumed. A t time t 6 i n Fig. 10, the charging
30 is stopped.
[00591
In the above described example case, the charging
current is gradually switched from 1 C t o 0.7 C t o 0.4 C t o
0 . 1 C. In a case where the charging current is switched from
1 C t o 0.8 C t o 0.6 Cto 0.3 C, the t i m e r e q u i r e d f o r completing
5 charging can be shortened as shown i n Fig. 11.
[0060]
In the above described first embodiment of the present
disclosure, the charging current is not turned on and off,
and generation of whisker-like noise accompanying switching
10 can be prevented. Further, as the charging current is made
smaller f o r a c e l l with a high voltage, the charging current
canbereduced. Thisexamplecanalsobeappliedtoamaterial
having a n o l i v i n e s t r u c t u r e . In such a case, V i s p r e f e r a b l y
set a t 3.55 V. The other d e t a i l s a r e the same as above, and
15 therefore, explanation of them is not made herein.
[0061]
<2. Second Embodiment of the Present Disclosure>
As shown i n Fig. 12, i n a second embodiment of the
present disclosure, a module balance discharging c i r c u i t is
20 added t o a c e l l balance discharging c i r c u i t 23. The module
b a l a n c e d i s c h a r g i n g c i r c u i t h a s a s e r i e s c i r c u i t o f a r e s i s t o r
r M and a switch s M connected between the p o s i t i v e side and
t h e negativeside o f a s e r i e s c i r c u i t of c e l l s ClthroughC16.
Therefore, when the switch s M is switched on, the r e s i s t o r
25 r M is i n s e r t e d i n p a r a l l e l t o the c e l l s C1 through C16.
Accordingly, when the switch s M is switched on a t a t i m e of
charging, the charging current is made lower. The switch s M
is switched on when the voltages of the c e l l s C1 through C16
become higher than a module balancing on-voltage Vmb (> Vov)
30 t h a t is s e t i n advance.
[0062]
[Control Operation]
Referring now t o the flowcharts i n Figs. 13 and 1 4 , the
control process a t a time of charging is described. Figs.
13 and 1 4 show the flow of a s i n g l e process, but the process
5 is dividedand showninthetwo flowcharts due t o l i m i t a t i o n s
of space. The control operation is the same as the process
according to the f i r s t embodiment, and Fig. 13 shows the same
process as t h a t shown i n Fig. 6. However, i n step S12', a
c h e c k i s m a d e t o d e t e r m i n e w h e t h e r V c e l l n i s e q u a l t o o r h i g h e r
10 than Vmb.
[OO63]
I f the r e s u l t of the above determination i n step S12'
is p o s i t i v e , t h e process moves on t o step S19 i n Fig. 1 4 .
Step Sl9: The switch s M is switched on, and the
15 inter-module balancing is enabled.
[0064]
Step S20: Acheckis made t o determine whethervcellmin
is equal t o o r higher than Vf. I f the r e s u l t of t h i s
determination is positive, the charging is completed (step
20 S5). Also, a check is made t o determine whether Vcell n is
equal t o or higher than Vov. I f the r e s u l t of the
determination is negative, the process moves on t o s t e p S13
(Fig. 1 3 ) .
[0065]
2 5 I f the r e s u l t of the determination i n step S20 is
p o s i t i v e , the process moves on to step S15 (the charging is
temporarilystopped). Theprocess thenmoves o n t o step S16.
[0066]
Step S16: I f t h e r e s u l t of the determination i n step
30 S6 is p o s i t i v e , or i f Vcell n is equal t o or higher than Vov,
t h e cell balancing is enabled only for cell ov having the
voltage equal t o or higher than Vov.
Step S17: A check is made t o determine whether Vcellov
is equal to or lower than Vn. I f t h i s condition is not
s a t i s f i e d , t h e p r o c e s s r e t u r n s t o s t e p S 1 6 ( t h e c e l l b a l a n c i n g
5 is enabled only for c e l l ov).
Step S18: I f the condition in step S18 is s a t i s f i e d ,
only the c e l l balancing t h a t was on p r i o r t o the charging
suspension process is enabled. The process then returns t o
step S l l (the charging continues) i n Fig. 13.
10 [0067]
[Exampleof Control AccordingtotheSecondEmbodiment]
Referring t o the graphs showing temporal changes i n
c e l l voltages i n Figs. 15 and 16, an example of control
according to the second embodiment is described. Figs. 15
15 and 16 show one s e t of graphs showing temporally continuous
changes, but the changes are divided and shown in the two
drawings due t o l i m i t a t i o n s o f space. In t h i s example, t h e
power storage unit BB is formed with series-connected four
c e l l s C 1 through C4, as i n the above described examples i n
20 the f i r s t embodiment. F i r s t , t h e voltages of the cells C1
through C4 gradually become higher with 1-C charging.
[0068]
When the voltage of the c e l l C2 reaches the current
switching voltage V 1 (4.05 V, f o r example) a t t i m e tl, t h e
25 switch s2 of the c e l l balance discharging c i ' r c u i t 23 is
switched on, and the charging current is reduced t o 0.7 C.
The charging is then continued. Before time tl, the voltage
r i s e curves o f the respective c e l l s run p a r a l l e l t o one
another. Since the switch s2 is switched on a t time tl, the
30 voltage rise curve of the cell C2 becomes gentler than those
of the other c e l l s . As the charging current is reduced, the
voltage r i s e curve becomes gentler a f t e r time tl.
[0069]
A t time t2, a c e l l other than the cell C2, or t h e cell
C1, for example, reaches the current switching voltage V2.
5 Therefore, the sr,~itchs l of the c e l l balance discharging
c i r c u i t 2 3 i s switchedon, and t h e c h a r g i n g c u r r e n t i s reduced
t o 0.4 C. After time t2, the voltage r i s e curve of the c e l l
C1 also becomes g e n t l e r than those of the other c e l l s C3 and
C4. As the charging current is reduced, the voltage r i s e
10 curve becomes even gentler a f t e r time t 2 .
[00701
A t time t3, the voltage of the c e l l C2 becomes higher
than the module balancing on-voltage Vmb. Accordingly, the
module balancing is enabled. As the module balancing is
15 enabled, the i n c l i n a t i o n o f t h e v o l t a g e r i s e curve a t the time
ofthechargingbecomesgentler. Also, a s t h e v o l t a g e r e a c h e s
Vov, the charting is not suspended. The charging with the
low charging current continues, and, a t time t 4 in Fig. 16,
Vcellminbecomes equal t o or h i g h e r t h a n v f , and the charging
20 is completed.
[00711
The present disclosure may also be embodied i n the
s t r u c t u r e s described below.
(1)
A power storage device including:
power storage u n i t s each i n c l u d i n g a t l e a s t o n e battery,
t h e power storage u n i t s being connected i n s e r i e s ;
cell balance u n i t s connected i n p a r a l l e l t o the
respective power storage u n i t s via switches; and
3 0 a control unit t h a t p e r f o r m s c o n t r o l t o chargethepower
storage units with a f i r s t constant current value, and, when
the power storage u n i t having the highest voltage among the
power storage u n i t s reaches a f i r s t p o t e n t i a l , connect the
corresponding one of the c e l l balance u n i t s t o the power
storage unit having the highest voltage, and switch the
5 charging current t o a second constant current value t h a t is
smaller than the first constant current value.
(2)
The power storage device of ( I ) , wherein, when a t l e a s t
one power storage unit other than the power storage u n i t
10 having the highest voltage among the power storage u n i t s
reaches a second p o t e n t i a l t h a t is higher than the f i r s t
p o t e n t i a l , the control unit performs control t o connect the
corresponding one of the c e l l balance u n i t s t o the power
s t o r a g e u n i t t h a t has reachedthesecondpotential, andswitch
15 the charging current t o a t h i r d constant current value t h a t
is smaller than the second constant current value.
(3)
The power storage device of (1) or ( 2 ) , wherein the
control unit is designedto s e t three ormore thresholdvalues
20 f o r switching the charging c u r r e n t .
( 4 )
The power storage device of ( I ) , ( 2 ) , or ( 3 ) , wherein,
when t h e h i g h e s t v o l t a g e among the power storage u n i t s
reaches a charging suspension voltage t h a t is higher than a
25 predetermined voltage and is lower than an overcharging
v o l t a g e , thechargingissuspended, andonlytheporierstorage
u n i t having the highest voltage is caused t o discharge, and
when the voltage of the power storage unit having the
highest voltage becomes equal t o a s e t voltage as a r e s u l t
30 of the discharging, the charging is resumed.
(5)
The power storage device of (I), (2), ( 3 ) , or (4),
wherein, r~7henthelowestvoltageamongthepowerstorageunits
becomes equaltoorhigherthanachargingcompletionvoltage,
the charging is completed.
5 (6)
The power storage device of (I), (21, (3), (41, or (51,
wherein, when the highest voltage among the power storage
u n i t s reaches a secondpotential t h a t is higher than the first
p o t e n t i a l , a switch of a balance unit connected i n p a r a l l e l
10 toalltheporverstorageunitsis switchedon, andtheconstant
current value is reduced.
( 7 )
The porier storage device of ( I ) , (2), (3), ( 4 ) , ( 5 ) ,
or (6), wherein the c e l l balance u n i t s each include a switch
15 and a r e s i s t o r t h a t are connected i n p a r a l l e l t o each
corresponding one of the power storage u n i t s .
( 8 )
The power storage device of (I), (2), ( 3 ) , (4), (5),
(6), or ( 7 ) , wherein the b a t t e r i e s included i n the power
20 storage units contain a positive-terminal a c t i v e material
having an olivine s t r u c t u r e .
(9)
A method of controLling a power storage device t h a t
includes :
25 power storage u n i t s eachincludingatleastonebattery,
t h e power storage u n i t s being connected in s e r i e s ;
cell balance u n i t s connected i n p a r a l l e l t o the
respective power storage u n i t s v i a switches; and
a control u n i t t h a t controls the cell balance units,
30 the method including performing control t o charge the
porier storage u n i t s w i t h a f i r s t constant current value, and,
when the power storage unit having the highest voltage among
the power storage units reaches a predetermined potential,
connect the corresponding one of the cell balance units to
the power storage unithavingthe highestvoltage, and switch
5 the charging current to a second constant current value that
is smaller than the first constant current value,
the control being performed by the control unit.
100721
<3. Applications>
[Power Storage System in a Residence]
Referring now to Fig. 17, an example where the present
disclosure is appliedto apower storage system for residence
is described. In a power storage system 100 for a residence
101, for example, electric power is supplied to a power
15 storage device 103 from a centralized power system 102 such
as thermal power generation 102~1,n uclear power generation
102b, and hydroelectric power generation 102c, via a power
network 109, an information network 112, a smart meter 107,
a power generation hub 108, and the like. I,n conjunction with
20 this, electric power from an independent power supply such
as a household power generating unit 104 is supplied to the
power storage device 103. The supplied power is stored in
the power storage device 103. With the power storage device
103, the electric power to be used in the residence 101 is
25 fed to the residence 101. The same power storage system as
above can be used not only in the residence 101 but also in
an office building.
[0073]
The powergeneratingunit104, power consuming devices
30 105, the power storage device 103, a control device 110 that
controls the respective devices, the smart meter 107, and
sensors 111 t h a t acquires various kinds of information are
provided i n the residence 101. The respective devices are
connectedbythepower network 109 andthe informationnetwork
112. Solar cells, f u e l cells, o r t h e l i k e are used as the
5 power generating unit 104, and generated e l e c t r i c power is
supplied t o the power consuming devices 105 and/or the power
storage device 103. The power consuming devices 105 are a
r e f r i g e r a t o r 105a, an a i r conditioner 105b, a t e l e v i s i o n
receiver 105c, a b a t h l 0 5 d , andthe l i k e . The power consuming
10 devices 105 f u r t h e r include e l e c t r i c vehicles 106. The
e l e c t r i c vehicles 106 are an e l e c t r i c car 106~1, a hybrid car
106b, and an e l e c t r i c motorcycle 106c.
100741
The above described power storage apparatus of the
15 presenidisclosureisappliedtotheporierstoragedevice 103.
The power storage device 103 is formed with 'secondary c e l l s
or capacitors. For example, the power storage device 103 is
formed with lithium ion c e l l s . The lithium ion c e l l s may be
of a s t a t i o n a r y type, or may be used i n the e l e c t r i c vehicles
20 106. The smart meter 107 has the function t o measure
commercial power usage, and transmit the measured usage t o
the electricpower company. Thepovrernetwork109maybe one
of or a combination of a DC power supply, an AC power supply,
and a non-contact power supply.
25 [0075]
The various sensors 111 may be a motion sensor, an
illuminance sensor, an object sensor, a power consumption
sensor, a vibration sensor, a contact sensor, a temperature
sensor, an infrared sensor, and the l i k e . Information
30 acquired by the various sensors 111 is transmitted t o the
c o n t r o l device 110. Weather conditions, the conditions of
a person, and the like are determined from the information
transmitted from the sensors 111, and the power consuming
devices105 canbe automatically controlled soas tominimize
energy consumption. Further, the control device 110 can
5 ,transmit information about the residence 101 to an external
electric power company or the like via the Internet.
[00761
The power generation hub 108 performs processing such
as power line branching or DC-AC conversion. The
10 communication method used by the information network 112
connected to the control device 110 may be a method using a
communication interface such as Universal Asynchronous
Receiver-Transmitter (UART), or a method using a sensor
networkcompliantv~ithwirelessc ommunication standards such
15 as Bluetooth (a registered trade name), ZigBee, or Wi-Fi.
Bluetooth (a registered trade name) is used in multimedia
communication, and enables point-to-multipoint
communication. ZigBee uses physical layers of Institute of
Electrical and Electronics Engineers (IEEE) 802.15.4.
20 IEEE802.15.4 is the name of short-range wireless network
standards called Personal Area Network (PAN) or Wireless (W)
PAN.
100771
The control device 110 is connected to an external
25 server 113. This server 113 may be managed by the residence
101,theelectricpowercompany, ortheserviceprovider. The
information to be transmitted and received by the server 113
is power consumption information, life pattern information,
electric power charges, weather information, natural hazard
30 information, andinformation r e l a t e d t o e l e c t r i c i t y t r a d i n g ,
for example. These pieces of information may be transmitted
and received by a power consuming device i n the house (such
as a t e l e v i s i o n r e c e i v e r ) , butmaybetransmittedandreceived
by a device outside the house (such as a portable telephone
device). These pieces of information may be displayed on a
5 device having a display function, such as a t e l e v i s i o n
receiver, a portable telephone device, or a Personal Digital
Assistant (PDA) .
[00781
The control device 110 t h a t controls the respective
10 components is formed with a Central Processing Unit (CPU),
a Random Access Memory (RAM), a Read Only Memory (ROM) , and
the l i k e , and is included i n the power storage device 103 i n
t h i s example. The control device 110 is connected t o the
power storagedevice 103, thehouseholdpowergeneratingunit
15 104,thepower:consumingdevices105,thevarioussensors111,
and the server 113 by the information network 112, and has
the function t o a d j u s t e l e c t r i c i t y u s a g e andpower generation,
f o r example. O t h e r t h a n t h a t , the controldevice110mayhave
t h e function t o conduct e l e c t r i c i t y trading in the
20 e l e c t r i c i t y market.
[0079]
As described above, not only e l e c t r i c power generated
from the c e n t r a l i z e d power system 102 such as the thermal
powergeneration102a, thenuclearpowergeneration102b, and
25 the hydroelectric power generation 102c, but also e l e c t r i c
power generated from the household power generating unit 104
( s o l a r power generation or wind power generation) can be
s t o r e d i n the power storage device 103. Accordingly, even
when the e l e c t r i c power generated from the household power
30 generating unit 104 varies, control can be performed so t h a t
t h e amount of power t o be sent out can be made constant, and
onlythenecessaryamountofpowerisdischarged. Forexample,
while e l e c t r i c porier obtainedthrough s o l a r power generation
is stored in the power storage device 103, l e s s expensive
night-time electric power is stored i n the power storage
5 device 103 a t night, so t h a t the e l e c t r i c power stored i n the
power storage device 103 can be discharged and used i n
expensive hours during the day.
[0080]
A l t h o u g h t h e c o n t r o l d e v i c e 1 1 0 i s i n c l u d e d i n t h e p o w e r
10 storagedevice103intheabovedescribedexample,thecontrol
device 110 may be included i n the smart meter 107 or may be
formed as an independent device. Further, the power storage
system100maybe usedin households inanapartment building,
or may be used i n detached houses.
15 [0081]
[Power Storage System i n a Vehicle]
Referring now t o Fig. 18, an example where the present
d i s c l o s u r e is applied t o a power storage system f o r vehicles
is described. Fig. 18 schematically shows an example
20 structureofahybridvehiclethatusesaserieshybridsystem
t o which the present disclosure is applied. A s e r i e s hybrid
system is a car t h a t is powered by a drive power converter,
using e l e c t r i c power generated by a generator t h a t is run by
an engine or the e l e c t r i c power t h a t is temporarily stored
25 i n a battery.
[0082]
This hybridvehicle 200includes an engine 201, apower
generator 202, a driving force conversion device 203, a drive
wheel 204a, a drive wheel 204b, a wheel 205a, a wheel 205b,
30 a b a t t e r y 208, a v e h i c l e c o n t r o l device 209, various sensors
210, and a charging i n l e t 211. The above described porier
storage apparatus o f t h e present disclosure is a p p l i e d t o t h e
b a t t e r y 208.
100831
The hybrid vehicle 200 runs with the driving force
5 conversiondevice203 servingasthepower source. Anexample
of the driving force conversion device 203 is a motor. The
driving force conversiondevice 203 is activatedbythepower
o f t h e b a t t e r y 2 0 8 , andthe rotativeforceofthedrivingforce
conversiondevice 203 is t r a n s f e r r e d t o t h e drive wheels 204a
10 and 204b. As DC-AC conversiori or reverse conversion (AC-DC
conversion) is performed a t appropriate sites, e i t h e r an AC
motorora DCmotorcanbeusedasthedrivingforceconversion
device 203. The various sensors 210 c o n t r o l t h e engine
revolving speed v i a t h e v e h i c l e c o n t r o l device 209, and
15 control the opening ( t h r o t t l e p o s i t i o n ) of a t h r o t t l e valve
(not shown). The various sensors 210 include a velocity
sensor, an acceleration sensor, an engine revolving speed
sensor, and the l i k e .
[0084]
20 The r o t a t i v e force of the engine 201 is transferred t o
thepowergenerator202, and, b y v i r t u e o f t h e r o t a t i v e force,
e l e c t r i c power generated by the power generator 202 can be
s t o r e d i n the b a t t e r y 208.
[0085]
25 As the hybrid vehicle slows down with a braking
mechanism (not shown), the r e s i s t i n g force during the
d e c e l e r a t i o n i s a p p l i e d a s r o t a t i v e f o r c e t o t h e d r i v i n g f o r c e
conversion device 203, and regenerative power generated from
t h e r o t a t i v e f o r c e b y t h e d r i v i n g force conversiondevice 203
30 is s t o r e d i n t h e b a t t e r y 208.
[0086]
The battery 208 can be connected t o a power supply
outside the hybrid vehicle, so as t o receive a power supply
fromthe e x t e r n a l power supply throughthe c h a r g i n g i n l e t 2 1 1
serving as a power i n l e t , and s t o r e the received e l e c t r i c
5 power.
[0087]
Although not shown i n the drawing, an information
processing device t h a t performs information processing
r e l a t e d t o vehicle control based on information about the
10 secondary c e l l s may be provided. Such an information
processing device may be an information processing device
t h a t i n d i c a t e s a remainingbatterylevelbasedoninformation
about the remaining b a t t e r y l e v e l .
[0088]
15 In the above description, a s e r i e s hybrid car t h a t is
powered by a motor using e l e c t r i c power generated by a power
g e n e r a t o r t h a t is runby the engine or t h e e l e c t r i c p o w e r t h a t
is temporarily stored in t h e b a t t e r y has been described as
an example. However, the present disclosure can also be
20 e f f e c t i v e l y applied t o a p a r a l l e l hybrid c a r t h a t uses power
outputs from both an engine and a motor serving as drive
sources, andsriitches amongthreemethods: beingpoweredonly
by the engine, being powered only by the motor, being powered
by both the engine and the motor. Furthermore, the present
25 d i s c l o s u r e can also be e f f e c t i v e l y applied t o a so-called
electric vehicle t h a t does n o t use an engine and is driven
only by a drive motor.
[0089]
<4. Modifications>
30 Although embodiments of the present d i s c l o s u r e have
been s p e c i f i c a l l y described so f a r , the present disclosure
is not limited t o the above embodiments, and various changes
based on the technical idea of the present disclosure can be
made t o them. For example, t h e s t r u c t u r e s , the methods, the
procedures, the shapes, t h e m a t e r i a l s , the numericalvalues,
5 and the l i k e m e n t i o n e d i n t h e above describedembodiments are
merelyexamples, a n d s t r u c t u r e s , methods, procedures, shapes,
materials, numerical values, and the l i k e t h a t d i f f e r from
thosementionedabovemaybeusedas necessary. For example,
the present disclosure can be applied t o systems other than
10 power storage systems.
REFERENCE SIGNS LIST
[00901
MOD, MOD1 - MODN Power storage module
15 ICNT Main c o n t r o l l e r
CNT Module c o n t r o l l e r
C1 - Cn C e l l
BB1 - BBn Power s t o r a g e u n i t
3 Bus
20 11 C e l l voltage multiplexer
12, 19 A/D converter and comparator
13 Monitoring c i r c u i t
16 Temperature multiplexer
20 Sub micro-controller unit
25 21 Communication unit
2 3 C e l l balance discharging c i r c u i t
30 Main micro-controller u n i t
rl - r16, r M Resistance
sl - s16, s M Switch
CLAIMS
1. A power storage device comprising:
a p l u r a l i t y of power storage units each including a t
5 l e a s t one battery, the power storage units being connected
i n s e r i e s ;
c e l l balance u n i t s connected i n p a r a l l e l t o the
respective power storage u n i t s v i a switches; and
a control unit configured t o perform control t o charge
10 the power storage u n i t s with a f i r s t constant current value,
and, when the power storage u n i t having the h i g h e s t voltage
among the power storage u n i t s reaches a f i r s t p o t e n t i a l ,
connect one of the c e l l balance u n i t s t o the power storage
u n i t h a v i n g t h e h i g h e s t v o l t a g e , andswitchachargingcurrent
15 t o a second constant current value smaller than the f i r s t
constant c u r r e n t value, the one of the c e l l balance u n i t s
corresponding t o the highest voltage.
2. The power storagedeviceaccordingtoclaim1, wherein,
20 when a t l e a s t one power storage unit other than the power
s t o r a g e u n i t having the highest voltage among the power
s t o r a g e u n i t s reachesa s e c o n d p o t e n t i a l h i g h e r t h a n t h e f i r s t
p o t e n t i a l , the control u n i t performs control t o connect one
of the cell balance units t o the power storage unit having
25 reachedthe secondpotential, andswitchthechargingcurrent
t o a t h i r d constant current value smaller than the second
c o n s t a n t c u r r e n t value, the one of the c e l l balance u n i t s
corresponding t o the power storage unit having reached the
second p o t e n t i a l .
30
3. The power storage device according t o claim 2, wherein
t h e control u n i t is designed t o s e t three or more threshold
values for switching the charging current.
4. The power storage device according t o claim 1, wherein,
5 when the highest voltage among the power storage u n i t s
reaches a charging suspension voltage t h a t is higher than the
f i r s t p o t e n t i a l and is lower than an overcharging voltage,
the charging is suspended, and only the power storage unit
having the highest voltage is caused t o discharge, and
10 when the voltage of the power storage unit having the
highest voltage becomes equal t o a s e t voltage as a r e s u l t
of the discharging, the charging is resumed.
5. The power storagedevice a c c o r d i n g t o c l a i m l , wherein,
15 rihenthelowestvoltageamongthepower s t o r a g e u n i t s becomes
equal t o or higher than a charging completion voltage, t h e
charging is completed.
6 . The power storagedevice accordingtoclaim1, wherein,
20 ~.rhenthehighestvoltageamongthepowerstorageunitsre aches
a second p o t e n t i a l higher than the f i r s t p o t e n t i a l , a switch
of a balance unit connected i n p a r a l l e l t o a l l the power
storage u n i t s is switched on, and the constant current value
is reduced.
25
7. The power storage device according t o claim 1, wherein
the c e l l balance u n i t s each include a switch and a r e s i s t o r
t h a t a r e connected i n p a r a l l e l t o each corresponding one of
the power storage u n i t s .
30
8. The power storage device according t o claim 1, wherein
the b a t t e r i e s included i n the power storage u n i t s contain a
positive-terminal active material having an o l i v i n e
s t r u c t u r e .
9. A method of c o n t r o l l i n g a power storage device,
the power storage device including:
power storage units eachincludingatleastonebattery,
the power storage units being connected i n s e r i e s ;
cell balance u n i t s connected in p a r a l l e l t o the
respective power storage u n i t s v i a switches; and
a c o n t r o l u n i t configured t o control the cell balance
u n i t s ,
the method comprising
performing control t o charge the power storage u n i t s
with a f i r s t constant current value, and, when the power
storage unit having the highest voltage among the power
storage u n i t s reaches a f i r s t p o t e n t i a l , connect one of the
c e l l balance u n i t s t o the power storage unit having the
h i g h e s t v o l t a g e , and switch a charging current t o a second
constant current value smaller than the f i r s t constant
c u r r e n t v a l u e , t h e o n e o f t h e c e l l b a l a n c e u n i t s c o r r e s p o n d i n g
t o the highest voltage,
the control being performed by t h e c o n t r o l u n i t .