Special Issue

Smart Grid

Development of UltraBattery
Hidehito Nakajima*, Tokunori Honma*, Kiyoshi Midorikawa*, Yuichi Akasaka*,
Satoshi Shibata*, Hideaki Yoshida*, Kensuke Hashimoto*, Yusuke Ogino*,
Wataru Tezuka*, Masaru Miura*, Jun Furukawa*, L. T. Lam*2, Sumio Sugata*3

We have developed UltraBattery (hereinafter called UB) for valve regulated
micro Hybrid Electric Vehicles (HEVs). The UltraBattery has a lead storage battery and an asymmetric capacitor in the same cell. The cycle life characteristics of the UB areabout the double of the existing lead storage batteries. We have also developed a stationary
UltraBattery for smart grid uses. It has high energy efficiencies, long cycle life characteristics andsuperior recovery characteristics when driving in partial charge states. This stationary
UltraBattery is at the stage of demonstration test in the “Kitakyushu Smart Community Creation
Project”, which is a subsidized project of the Ministry of Economy, Trade and Industry.

ABSTRACT1.

INTRODUCTION

In recent years, there is an increasing need for reduction
in CO2 emission and for the use of renewable energy inautomobiles as mitigations against global warming.
Mileage regulations and CO2 emission regulations forautomobiles are becoming stricter year after year domestically and in the United States and Europe. Therefore,
automobile makers around the world have been launching idling stop system (ISS) vehicles, micro HEVs and full
HEVs which are contributing to improved fuel efficiencies.
Also, the need for the use of renewable energy is increasing not only from the viewpoint of mitigation against global warming but also from a problem of tight power supply
caused by the power condition in recent years and also
from an efficient use of power by smart communities.
Given these factors, storage batteries have been thefocus of the attention. The requirements for their applications have been expanding from the existing standby
uses, such as for starting engines and for emergency
power, to the cycle use which consists of repeated andfrequent charge and discharge.
In this report, we describe the characteristics of two
types of developed UBs for cycle uses, one is for a vehicle installation type and another is for a stationary type. In
the last part, we describe the “Kitakyushu Smart* UB Commercialization Division, Strategic Planning Office,
The Furukawa Battery Co., Ltd.
*2 CSIRO (Commonwealth Scientific and Industrial Research
Organization), Division of Energy Technology, Melbourne,
Australia.
*3 New Business Development Department, The Furukawa
Battery Co., Ltd.

Community Creation Project”. This is one of the “NextGeneration Energy and Social System Demonstration
Projects”, which are subsidized by the Ministry of
Economy, Trade and Industry.

2.

UltraBattery FOR AUTOMOBILE

ISS vehicles mean the automobiles with an idling stop
system, and micro HEVs mean the automobiles with acharging function using breaking energy recovery in addition to an idling stop function. Full HEVs mean the automobiles with motors and generators 1). They can drive
only with electricity at startup and at low speed drive2).
Hereafter, we describe the circumstances of automobiles and batteries in Europe. In 2012, the sales of micro
HEVs accounted for about 40% of the automobile sales in
the whole 27 countries in EU. The sales are expected toreach or exceed 60% in 20153). It indicates that the market
of batteries for the micro HEVs will grow significantly inthe future.
The load of installed lead storage batteries between
micro HEVs and existing automobiles is significantly different. For example, in micro HEVs, power for electricallydriven devices such as lights and audio systems are all
supplied from batteries and the discharge is deeper thanin the existing automobiles. That is because power is not
generated by alternators when micro HEVs stop idling.
Also, as micro HEVs restart the engines each time theystop idling, the number of large-current discharges
increases compared with existing systems. Moreover, as
the charge by recovery brakes needs to be accepted efficiently, batteries are used in the partial state of charge(PSOC), which means that the batteries are used at about
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Development of UltraBattery

90% state of charge (STOC). Therefore, lead storage batteries for micro HEVs require both a charge acceptanceand a resistance in the PSOC4).
Given these factors, we have developed the UB forvalve regulated micro HEVs.

resistance) of positive active materials. In addition, we
adopted our company’s “C-21 alloy” as a positive lattice
alloy to keep a high corrosion resistance and the longterm stability of the mechanical characteristics in hightemperature environments11).

2.1

2.1.2 Positive and negative lattice
The optimization of the number of polar plates, the formsof lattices and the sizes of lattices are the available measures for enhancing the output characteristics12). We optimized the forms of lattices (addition of reinforced lattices,
refinement of lattices) by computer simulation because it
is desirable to have a uniform distribution of potentials toincrease the rate of utilization of active materials. Figure 3
shows the results. The distribution of potentials improved
after the optimization.

Development of UB for Valve Regulated Micro
HEV
UltraBattery is a hybrid battery in which a lead storage
battery and asymmetric capacitors are installed in thesame cell. Figure 1 shows the shape and Figure 2 shows
the construction5). The UB can be used under severe conditions in which the PSOC and large current pulse
charge-discharge are combined, which was difficult to beachieved with lead storage batteries.6)-9).
In order to develop the UB suitable for micro HEVs, we
adopted a part of high-performance technologies of 36 V
valve regulated lead acid (VRLA) developed for mild
HEVs and enhanced the performance further. The following shows the developed items.

Potential
/ mV
110

0
Positive / Before improvement

Figure 1 Shape of valve regulated UltraBattery for micro HEV.

–

+

PbO 2
PbO2

Capacitor
electrode

Pb

Potential/ mV
80

Asymmetric capacitor
+
i

i1

i

–

0
Negative / After improvement

Figure 3 Analysis of distribution of potentials.

Pb

i2

Capacitor electrode

UltraBattery

PbO 2

Potential
/ mV
80

0
Negative / Before improvement

Lead storage
battery0
Positive / After improvement–+

Separator

Potential/ mV
110

Separator

Figure 2 Construction of UltraBattery.

2.1.1 Positive plate
Positive and negative active materials repeat dissolutionprecipitation at charge and discharge. Positive active
materials lose the original solid backbone structure gradually by the dissolution-precipitation and it causes softening. We adopted active materials which are denser thanthe existing ones to enhance the resistance (softening

2.2 Life Test of UB for Micro HEV
2.2.1 Test condition
Batteries in micro HEVs are used at about SOC90%(PSOC) to accept the charge generated by recovery
brakes efficiently. We tested under the condition of
SOC70%, which is severer than that of 90%. In line, we
tested under the conditions of SOC80% and 90% toinvestigate the effects of SOC on the lives of the batteries(Test condition ① SOC70%, ② SOC80%, ③ SOC90%).
The test profile is a pulse charge-discharge pattern withthe maximum discharge current of 4 CA.
2.2.2 Test result
Figure 4 shows the relationships between the SOC andthe capacity turnovers. The test conditions are ①-③. The
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Development of UltraBattery

depth of discharge (DOD) is 5%. For comparison, weshow the results of an existing storage battery tested
under the conditions of same capacity and of SOC70%. A
capacity turnover is obtained by dividing the sum of theelectrical charge which is available before the battery’slife ends by the battery’s rated capacity. A comparison oflife cycles becomes possible by comparing capacity turnovers.
The relation between the SOC and the Capacity turnovers shows that as the SOC increased from 70%, 80% to90%, the capacity turnovers became higher. On the other
hand, the UB battery had about 1.8 times as much capacity turnover as the existing one under the condition of
SOC70%.
This result means the life of the UB is longer than thatof the existing battery. After these tests, we disassembled
the batteries. In the existing battery, the softening of thepositive active materials and a significant sulfation of thenegative active materials were observed. On the other
hand, in the UB, although positive active materials wereobserved, noticeable sulfation of the negative active
materials was scarce.

Capacity turnover

1000
800

Existing battery
UB

600
400
200
0

70%

80%
SOC

0.6C10A, and conducted a recovery charge after that. The
quantity of charge-discharge electricity is equivalent to
10% of the rated capacity. Given the sum of the discharged electrical quantity per operation day is 50% of
the rated capacity, five cycles are equivalent to thecharge-discharged electrical quantity a day. Therefore, 30
cycles are equivalent to the operation for six days. Testing
conditions were set assuming that operations are conducted from the first to the sixth day and a recovery
charge is conducted on the seventh day of a week.
Figure 5 shows the Wh efficiencies during the cycle tests.
As figure 5 shows, in the case of 0.1C10A charge-discharge, the Wh efficiencies were high although they varyfrom 91% to 94.5% depending on the SOCs. When thecycle of discharge0.6C10A-charge0.45C10A was tested,
the Wh efficiencies tended to decrease because thepolarization of the voltage became larger. Nevertheless,the Wh efficiencies were 83%-87%, which were still highvalues.
Table 1

Condition of Wh efficiency test.

Charge-discharge
rate (C10A)

SOC (%)

Remarks
SOC adjustment①

Discharge

0.1

10-100%(Per 10%)

②

Break

−

−

10 min③

Discharge 0.10 0.20 0.40 0.60

-10%

④

Charge0.10 0.20 0.40 0.45

10%Repeatcharge-discharge(③-④)
for 30 times

⑤

Break

−

−

10 min⑥

Charge0.2

100％

Recovery charge

90%
100

0.1C10A
0.2C10A
0.4C10A
Dis0.6C10A-Cha0.45C10A

3.

STATIONARY UltraBattery

Stationary storage batteries have been considered as
devices for power storage and output leveling. Therefore,
they require a long-lived performance under the conditions of large-current charge-discharge and of PSOC. We
have developed a stationary UB suitable for these purposes.
3.1 Characteristic Evaluation in PSOC
3.1.1 Wh efficiency test
We report the characteristics of the stationary UB in
PSOC. When storage batteries are used in a stationary
state, they need equal or exceed 10 years of life.
Therefore, energy efficiency is an important point. We
evaluated UB1000 (2 V-1000 Ah/10 h) under the conditions stated in Table 1 to calculate the Wh efficiency of the
UB. SOC was adjusted by steps of 10%. We conducted
30 cycles of charge-discharge at the rates of 0.1C10A-

Watt-hour efficiency (%)

Figure 4 Relationship between SOC and capacity turnover.
95

90

85

80

0

20

40

60
SOC (%)

80

100

Figure 5 Result of Wh efficiency test (cycle test only).

3.1.2 Input-output characteristic test
Next, we report the results of input-output characteristic
tests in PSOC. Figure 6 shows the profiles of the inputoutput tests at SOC50% (indicated by the red line). After
SOC was adjusted to 50%, tests were conducted at the
charge-discharge currents of 0.1C10A, 0.2C10A, 0.3C10A,
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0.4C10A, 0.6C10A, 0.8C10A, 1C10A, respectively (indicatedby the blue lines). The ambient temperature was set at
25°C. Charge-discharge was conducted for 30 seconds ateach rate and a break was given for 10 minutes after eachcharge-discharge. The operable range of the battery voltage was set at 1.8 V-2.35 V (indicated by the orange
lines). This is because batteries’ lives could be shortenedby over discharge if the charge voltage is under the lower
limit of 1.8 V, and because drawdown of the moisture inelectrolyte is accelerated by electrolysis and the loss ofthe charged energy could occur if the charge voltage isover the upper limit of 2.35 V. As the figure shows, the discharge voltages did not fall below the lower limit of 1.8 V
at any current values, but the charge voltages exceeded
the upper limit of 2.35 V at 0.8C10A and 1C10A. That is, themaximum discharge current was 1C10A and the maximum
charge current was 0.6C10A at SOC50%. These values
were higher than those of the existing batteries (compared with our existing products).

Operational
range

Voltage (V)

2.2
2

1.5
1

1.8

0.5

1.6

0

1.4

-0.5

1.2

-1

1

Voltage
Rate of charge or discharge
0

50

100
Time (m)

150

-1.5
200

Figure 6 Profile of input-output characteristic tests.

3.2 Cycle Life Characteristics
3.2.1 PSOC cycle life test
We evaluated the cycle characteristics of the UB1000 (2V-1000 Ah/10 hr) when it was operated in PSOC for a long
period. The following (1)-(3) show the test conditions9).
(1) Cycle condition (temperature: 25°C)· Start at SOC60%· Discharge : 0.1C10A × 3 h· Break : 1 h· Charge : 0.1C10A × 3 h· Break : 1 h(2) Condition of recovery charge (temperature: 25°C)· Conducted per 90 cycles (1 month)· Charge: 0.1C10A, charge voltage 2.45 V × 20 h(3) 10 hour rate capacity test after recovery charge(temperature: 25°C)· Discharge : 0.1C10A, final voltage 1.8 V
In this test, the cycle of SOC60%⇔SOC30% was

100
Initial capacity ratio (%)

2

2.4
SOC50%

105

2.5

Over

Rate of charge or discharge (CA)

2.6

repeated for three times a day, a recovery charge per 90
cycles was conducted to recover the SOC up to 100%,
then the changes in 0.1C10A discharge capacities wereconfirmed. In general, when lead storage batteries repeat
the cycle in such a PSOC operation, the recovery charge(full charges) is conducted per one week to remove thelead sulfate accumulated on the polar plates by oxidizing
it on the positive electrodes and resolving it on the negative electrodes. This is for avoiding the decrease of thedischarge capacities caused by the growth of lead sulfate’s crystals. In this test, the recovery charge was notconducted for 1 month. Therefore, it was a severer test
condition for PSOC evaluation. The existing cell and the
UB were used for the test batteries.
Figure 7 shows the changes in the initial capacity ratios.
The longitudinal axis shows the initial capacity ratios (%)
of 0.1C10A capacity. The capacity ratio of the existing cell
after 270 cycles was 93%, which was a moderate declining trend.

Still on test

95

90

85

Control
UltraBattery

80

0

100

200
Number of cycles

300

400

Figure 7 Changes in initial capacity ratio in PSOC cycle test.

On the other hand, the UB kept equal or exceeding
103% after 270 cycles. That is, the cycle characteristics of
the UB are superior under the PSOC condition. It alsomeans that the recovery charge characteristics of the UB
are superior.
Figure 8 shows the changes in the positive and thenegative potentials during recovery charge after the cycle
test for 180 times. Figure 9 shows the changes in the
charge currents and the charge capacities during recovery charge after 180 cycles. In the figure 8, the negative
potential of the existing cell is polarized to the negativeside along with the beginning of the recovery charge.
This is because the crystals of the lead sulfate grew andaccumulated to be a resistance in the negative active
materials during the PSOC cycle test. The UB restrained
the accumulation of the lead sulfate during the PSOC test
because no significant polarization was observed in thenegative potential of the UB. Also, figure 9 shows that in
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1.4

0

1.2

-0.2

1

-0.4

Positive potential of control
Positive potential of UltraBattery
Negative potential of control
Negative potential of UltraBattery

0.8

-0.6

0.6

-0.8

0.4

-1

0.2

-1.2

0

0

1

2

3

4

5

Negative potential (V vs.Hg/Hg2SO4)

Positive potential (V vs.Hg/Hg2SO4)

the UB, the droop of the charge current is slower due tothe smaller polarization in the negative potential. Alongwith that, the charge capacity of the UB is bigger than theexisting cell. Also, the UB was confirmed to have a superior charge acceptance compared with the existing cell.
The UB has a possibility of extending the interval of therecovery charge significantly compared with the existing
lead storage batteries. The reduction in the quantities of
the recovery charge, the enhancement of the operational
efficiencies and the Wh efficiencies can be made possible
by extending the interval of the recovery charge.

-1.4

Time (h)temperature was set at 25°C. After adjusting the SOC to
50% at 1C1A charge current, the cycle of a discharge
1C1A for 6 minutes-a break for 5 minutes-a charge 1C1A
for 6 minutes-a break for 5 minutes was repeated for 1000
cycles. After that, we conducted a 1C1A capacity test.
In addition, when the charge final voltage reached 2.45
V and the discharge final voltage reached 1.75 V during
the cycle, we conducted the 1C1A capacity test and continued the cycle test.
Figure 10 shows the changes in the discharge terminal
voltages during the cycle test. Figure 11 shows thechanges in charge terminal voltages. No significant gap
was observed between the two batteries with respect tothe changes in the discharge terminal voltages during thecycle test. However, with respect to the charge terminal
voltages, the voltage of the UB scarcely reached thecharge terminal voltage. On the other hand, the voltage ofthe existing storage battery frequently reached the charge
terminal voltage. The fact indicates that the charge voltage of the UB is stable, thereby keeps a good charge
acceptance.
Figure 12 shows the changes in 1C1A initial capacity
ratios. Compared at the point where the capacity ratios
dropped to 80%, the life of the UB is twice as longer asthat of the existing lead storage battery. The UB shows
good cycle life characteristics at high rate charge-discharge currents under the condition of the PSOC.

600

100

500

80

400
Charge current of control
Charge current of UltraBattery 300
Charge capacity of control
Charge capacity of UltraBattery
200

60
40
20

Discharge terminal Voltage (V)

120

2.1

Charge capacity (Ah)Charge current (A)Figure 8 Changes in positive and negative potentials during
recovery charge after 180 cycles.

2.0

1.9

1.8

UltraBattery

100
1.6

0

Control

1.7

0

5

10
Time (h)

15

20

0

Figure 9 Changes in charge current and charge capacity during
recovery charge after 180 cycles.

0

2000

4000
6000
8000
Number of cycles

10000

12000

Figure 10 Changes discharge terminal voltage during HR-PSOC
cycle test.

3.2.2 HR-PSOC cycle life test
Next, we conducted high rate partial state of charge(HR-PSOC) cycle test in which a cycle test is repeated at
high-rate charge and discharge currents under the PSOC
condition13). The UB500 (2 V-500 Ah/10 hr) was used forevaluation and the existing lead storage battery with thesame capacity was used for comparison. The ambient
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Development of UltraBattery

Charge terminal Voltage (V)

2.5

2.4

2.3

2.2

Control
UltraBattery

2.1

0

2000

4000

6000

8000

10000

12000

series x 2 parellel) in Maeda Area (Figure 13), 192 cells of
the UB500 and 32 cells of the UB100-6 (6 V-100 Ah/10 hr)
in the Kitakyushu Museum of Natural History and Human
History (Figure 14), 32 cells of the UB 100-6 in the HumanMedia Creation Center／KYUSHU (Figure 15). The demonstration test has started in 2012. In the future, we will
demonstrate the superiority of the UBs from the viewpoints of energy efficiencies, equalized charge intervals
and elongation of the lives of storage batteries.
This project is being undertaken by the outcomes of the
NEDO’s collaborative research, “Technical developmentof the complex systemization of storage”, and by the
Ministry of Economy, Trade and Industry’s subsidized
project, “Next-Generation Energy and Social System
Demonstration Project”.

Number of cycles
Figure 11 Changes in charge terminal voltage during HR-PSOC
cycle test.

110

1hr capacity ratio (%)

100

Control
UltraBattery
Life line

90

80

70
Figure 13 UB1000 × 336 cells, Maeda-Area.

60

50

0

2000

4000
6000
8000
Number of cycles

10000

12000

Figure 12 Changes in initial capacity ratio in HR-PSOC cycle test.

4.

PARTICIPATION IN THE KITAKYUSHUSMART COMMUNITY CREATIONPROJECT

Yahata Higashida-area, Kitakyush-city was selected as
one of the four regions where the Ministry of Economy,
Trade and Industry conducts the Next-Generation Energy
and Social System Demonstration. The name of the project is the Smart Community Creation Project, which isaiming at reducing 50% of the CO2 and at maintaining theelectrical quality at the introduction of new energy14).
In this project, our company has completed the installations of the UBs in cooperation with the community energy management system (CEMS) for the purpose ofadjusting the supply-demand of energy and for supplying
power at times of disaster and at the times of massive
black out. We have installed 336 cells of the UB1000 (168Figure 14 UB500 × 192 cells, Kitakyushu Museum of Natural
History and Human History.

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Development of UltraBattery

PCS

BMS

BMU - 1
BMU - 2
Wireless

Figure 15 UB100-6 × 32 cells, Kyushu Human MediaCreation Center.

SENSOR

UltraBattery

SENSOR

UltraBattery

SENSOR

UltraBattery

SENSOR

UltraBattery

Figure 16 Battery Management System.

5.

BATTERY MANAGEMENT SYSTEM

The battery management system (BMS) is the importantsystem to protect storage batteries and to grasp theremaining capacities in storage systems, and to maintainhigh reliabilities of the systems. We have installed a BMS
in the storage system of the Kitakyushu Smart
Community Creation Project in joint development with
Furukawa Electric Co., Ltd.
Figure 16 shows how the scheme of the BMS. Battery
monitoring unit -1 (BMU-1) manages the currents, voltages and the temperatures of the whole assembled batteries. BMU-2 manages each battery’s voltage, its inner
impedance and the battery temperature which is transmitted from battery condition watcher (BCW) attached toeach battery. The BMS aggregates and manages the dataof the BMU-1 and -2, and transmits the information of
SOC and state of health(SOH), etc. to PCS. The installation of the BMS enables the status determination of thestorage batteries under the PSOC conditions, the lifetime
determination by the inner diagnosis function in eachcells and the transmission of the data of the storage battery statuses by connecting to a LAN. By installing the
BMS in this demonstration, we received successive dataof the storage battery status, we will be able to discover
the behaviors of the storage batteries in operation, theimprovement points and the problems. Their countermeasures and their improvements enable the optimization of
the operation system.

6.

CONCLUSION

We have developed the UB battery for micro HEVs whosebattery life is 1.8 times longer than that of the existing batteries. We disassembled the batteries after the tests. As aresult, the existing battery had softened positive active
materials and significantly sulfated negative active materials. On the other hand, the UB had softened positive
active materials, although it had scarce significantly sulfated negative active materials. This is one of the reasons
why the UB obtained a good lifetime characteristics.
We obtained the following achievements in the development of the stationary UB.
(1) The stationary UB showed the Wh efficiencies of
91-94.5% in 0.1C10A charge-discharge, and 83-87%
in discharge 0.6C10A-charge0.45C10A in the range
of SOC30-90%. That is, the UB had high Wh efficiencies not only in low charge-discharge currents
but in high charge-discharge currents.
(2) The stationary UB had good capacity ratios ofequal or exceeding 100% despite a recovery
charge of once per 90 cycles in the PSOC test. It
was also confirmed to have a superior recovery
charge characteristics.
(3) The life performance of the stationary UB was
about the double of the long-lived lead storage battery in the HR-PSOC test.
By the results above, we confirmed that the stationary
UB has high energy efficiencies, superior lifetime characteristics and superior recovery charge characteristics
under the PSOC condition.
We have been participating in the Kitakyushu Smart
Community Creation Project, and as a member of thisproject, we have installed the developed stationary UBs
and have started the demonstration in 2012.

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