Rechargeable Battery Expo 2014: Regenerative energy storage devices

New uses for capacitors and nickel metal-hydride battery systems



Two-seater electric vehicle "Miluira" powered by lithium-ion capacitors (exhibited by Asahi Kasei FDK Energy Device)

 The 5th International Rechargeable Battery Expo was held at Tokyo Big Sight on February 26 to 28, 2014. This report highlights the exhibitions of storage devices for start-stop systems and brake energy regeneration systems.
 Demand for start-stop systems is increasing rapidly as a cost-effective fuel-saving technology. However, load of the system is too large for ordinary lead-acid batteries and special batteries have been developed exclusively for use with start-stop systems. Concurrently, storage devices that assist lead-acid batteries have been increasingly used. These storage devices include electric double layer capacitors, lithium-ion batteries and nickel metal-hydride batteries.
 The exhibitors also displayed capacitors used as storage devices in electric and hybrid vehicles. Electric double layer capacitors by Ioxus and lithium-ion capacitors by JM Energy are used in hybrid buses in markets outside Japan.

 This report also introduces an energy regeneration system with nickel metal-hydride batteries, developed by Panasonic, as an example of new storage devices (The product was not exhibited at the Expo). The batteries are supplied to Nissan and Mitsubishi Motors for their start-stop systems.

Storage devices for start-stop and energy regeneration systems

Storage devices Usage case in Japan Suppliers Description
Special lead-acid batteries Many Lead-acid battery
Special lead-acid batteries are developed with enhanced input characteristics and cycle life.

New devices
Electric double
layer capacitor
Mazda & Honda
Nippon Chemi-con New devices assist lead-acid batteries, enhance charging and discharging capacities, and extend their service life.
Lithium-ion battery Suzuki
(Enecharge system)
Nickel metal-hydride
Nissan & Mitsubishi

Related reports: The International Rechargeable Battery Expo 2013 (posted in March 2013)

Electric double layer capacitors

 Unlike the secondary batteries that store electric energy by chemical reactions, electric double layer capacitors (EDLC) store energy by absorption and desorption of ions in the electrolytic solution. The EDLC are therefore less prone to degradation over extended use. Secondary batteries are prone to degradation due to frequent chemical reactions and therefore have a short cycle life. The EDLC are also capable of quickly charging and discharging high current electricity and are often used for starting 12-cylinder engines, heavy-duty trucks in cold areas. However, they only have a small storage capacity and are likely to be used in combination with a  lead-acid battery or a lithium-ion battery.


EDLC by Nippon Chemi-Con, Ioxus and Maxwell

 Nippon Chemi-Con exhibited its EDLC that are supplied to Mazda and Honda. Focusing on "fast charge," Mazda is striving to increase fuel efficiency by supplying electricity from EDLC to onboard electric equipment and reducing load to the alternator. In contrast, "fast discharge" is the priority for Honda and its start-stop system uses only capacitors to restart the engine. The start-stop systems developed by Mazda and Honda do not require replacement of the EDLC during the vehicle's operational life.

 Ioxus is a new capacitor manufacturer that was established in 2007 in the United States. In 2012, the company acquired Power Systems from Mitsui & Co., Ltd. and Omron Corporation. Ioxus plans to expand use of the EDLCs for onboard applications such as energy regeneration systems and back-up power supply for a variety of control-by-wire systems. The company exhibited its EDLC modules which are used on buses in China.

 Maxwell Technologies exhibited its module which will be used to start engines of heavy-duty trucks in cold areas in North America. The EDLC are used in Japan as a power source for  compactor devices of garbage collection trucks.


EDLC EDLC supplied by Nippon Chemi-Con for Honda's Fit/Vezel EDLC EDLC supplied by Nippon Chemi-Con for Mazda's all-new Axela (5 cells x 2 stacks for space efficiency)
Module used in hybrid buses in China Module used in hybrid buses in China (exhibited by Ioxus) Engine starting module Engine starting module supplied by Maxwell Technologies for heavy-duty trucks in cold areas in North America


Electric double layer capacitors (EDLC)

Nippon Chemi-con Expanding EDLC business  Nippon Chemi-Con's EDLC for automotive use (marketed under the trade name of "DLCAP") feature operational temperature range increased from -25°C through +60°C to -40°C through +70°C. The improved thermal resistance makes the EDLC ready for use in the engine room. The improved cold tolerance makes them fully operational in severely cold climate.
 After the expansion of the onboard EDLC business, Nippon Chemi-Con expects its sales from the EDLC business for the fiscal year ending March 2014 (FY 2013) to increase to JPY 4 billion, ten times growth over FY  2011 before the onboard business commenced. The company plans to expand non-onboard EDLC business as well to achieve annual sales of JPY 10 billion for FY 2015.
For Mazda vehicles  In addition to the Mazda Atenza and the CX-5 sold in China, the EDLC are used in the deceleration energy regeneration system "i-ELOOP" in the SKYACTIV-G20 and SKYACTIV-D2.2 on the new Axela launched in November 2013. The company exhibited a module made up of ten DLCAPs.
 The system collects energy of deceleration and stores it in the large-capacity capacitor. This reduces load to the alternator when the vehicle accelerates. The engine is started using electricity supplied by lead-acid battery. The energy stored in the capacitor is not used for starting the engine.
For Honda vehicles  The EDLC are supplied in the form of a deceleration energy regeneration system on Honda's Fit powered by 1300cc gasoline engine and the Vezel powered by 1500cc gasoline engine, each with the start-stop system feature. Nippon Chemi-Con supplies a module that consists of six DLCAPs. The system, called "capacitor-powered start-stop system" by Honda, has achieved fuel efficiency of 26.0km/ liter (JC08 test cycle) with the Fit (FWD/CVT) powered by 1300cc gasoline engine.
 The electric energy regenerated by the alternator during deceleration is stored in the EDLC. It is supplied to electric equipment while the engine is stopped by the start-stop system. The company has also adopted the world's first starter motor system in which the motor is energized only by electricity stored in the EDLC.
IOXUS Japan Hybrid bus  Ioxus exhibited its EDLC module that is supplied for hybrid buses in China. The EDLC contribute to about 40 percent improvement of the bus's fuel efficiency. Ioxus reportedly plans to expand the use of its EDLC for hybrid buses and wind power generation in China.
Maxwell Technologies Engine Start Module (US)  Maxwell Technologies exhibited its engine starter module for heavy-duty trucks used by trucking companies in North America. The module supports stable engine start in cold areas and enables downsizing of lead-acid batteries or reduction of the number of batteries required.
Start-stop system (Europe)  The battery is packaged by Continental AG for onboard use in Europe. The package is used in PSA's "e-HDi" start-stop system for diesel-fueled vehicles (mainly for restarting the engine) and in the start-stop system on Lamborghini Aventador (for restarting the 12-cylinder 700hp engine).
compactor devices for Electric garbage collection trucks (Japan)  The batteries are used in Japan to supply electric power to ShinMaywa Industries' compactor devices on electric garbage collection trucks.

(Note) Maxwell Technologies' products were introduced at the Expo by Kyokuto Boeki, its Japanese agency, and by Kuzumi Electronics Industries, a Japanese engineering company which develops products by integrating the EDLCs.



Lithium-ion capacitors

 The cathode of a lithium-ion capacitor is made of the same active carbon as that of the EDLC. The anode of the lithium-ion capacitor consists of the same lithium-doped carbon material as that of the lithium-ion battery. The  lithium-ion capacitor has higher energy density than the EDLC and higher output density than the lithium-ion battery. Additionally, the lithium-ion capacitor last over more than a million cycles of charge and discharge as does the EDLC. For these reasons, the  lithium-ion capacitor are broadly used for fast charge and discharge, energy regeneration, peak assisting and equalization of electric power. The  lithium-ion capacitor manufacturers are working on expanding its use to automobiles, buses and railways.

Lithium-ion capacitors versus electric double layer capacitors

Lithium-ion capacitor Electric double layer capacitor (EDLC) Lead-acid battery Lithium-ion battery
Max. voltage (V) 3.8 2.5 2.0 4.2
Energy capacity (Wh)
Output (W) ×
Cycle characteristics ×
Temperature range (°C) -20 to 80 -20 to 60 -30 to 50 -20 to 60

Source: Asahi Kasei FDK Energy Device's display material at the Expo (Note) In the above table, ◎ stands for "Excellent", ○ for "Good", △ for "Limited", × for "Low" performances.


Lithium-ion capacitors by JM Energy, Asahi Kasen FDK Energy Device, and Shin-Kobe Electric Machinery

 JM Energy, an affiliated company of JSR, produces laminated and rectangular types of lithium-ion capacitors. The company exhibited its lithium-ion capacitor module that is used in city buses in the United Kingdom.

 The company has announced it would invest JPY 6 billion to build a new plant, with an annual capacity of 3 million cells, in the site adjacent to the existing plant in Yamanashi Prefecture. Shipment will start in June 2015. The company currently has annual capacity to produce 300,000 laminated cells and 120,000 rectangular cells.

 Asahi Kasei FDK Energy Device (AFEC) exhibited ultra-micro electric vehicle "Miluira" that runs exclusively on the lithium-ion capacitor. The company also exhibited its newly-developed high-energy cells and high-power cells. Shin-Kobe Electric Machinery exhibited its lithium-ion capacitor sold under the trade name of "LCAP."


Lithium-ion capacitors

JM Energy Hybrid bus  JM Energy exhibited its lithium-ion capacitor module that is used on hybrid city buses in the United Kingdom. Twelve modules, each consisting of 15 "CPP3300S" rectangular cells with a rated output of 2.2V to 3.8V, are mounted on the bus's rooftop. The regenerated energy of deceleration is stored in the lithium-ion capacitor and used to assist the engine during acceleration. This leads to 35 percent improvement in fuel efficiency.
 JM Energy's lithium-ion capacitor are marketed in Europe by JSR Micro N.V., a sister company of JM Energy located at JSR Group's Belgian headquarters. The cells are packaged by Bluways (headquartered in the U.S.), a manufacturer of electric systems for buses and other large vehicles. Bluways takes orders and delivers the packages to bus companies. JM Energy's  lithium-ion capacitor need no replacement over the life cycle of the buses.
Asahi Kasei FDK Energy Device EV Miluira  The two-seater EV powered exclusively by lithium-ion capacitor measures 2360mm in length, 1200mm in width and 1400mm in height. The EV weighs 350kg and has 864Wh energy capacity. It can run up to 13km after 3.6 minutes of fast full-charge from a 200A source. The EV itself is manufactured by Takayanagi Co., Ltd. located in Hamamatsu City.
Asahi Kasei FDK Energy Device Standard item  The company's standard item is marketed under the trade name of "EneCapTen."
High-energy cell  AFEC has developed a high-energy cell, FSC40RA, with energy density (Wh/liter) increased by 70 percent from standard products. The new  lithium-ion capacitor extend operating time and driving range. It can be used as back-up or main power supply for micro vehicles and automatically guided vehicles (AGV).
High-powercell  The company also has developed high-power cells, FSC10XA, having a higher output density (kW/liter). The new  lithium-ion capacitor increase the energy regeneration efficiency when used for assisting regeneration on automobiles, railways, etc.
Shin-Kobe Electric Machinery LCAP  Shin-Kobe Electric Machinery exhibited its cylindrical lithium-ion capacitor sold under the trade name of "LCAP." It is used as auxiliary power supply, main power supply, electric regeneration and back-up power supply on construction machinery and industrial machinery.



Use of nickel metal-hydride batteries

 Panasonic has developed "12V energy regeneration system" that uses nickel metal-hydride (Ni-MH) batteries. FDK has developed Ni-MH batteries that can withstand up to -40°C temperature.


Nickel-MH battery with a heater "Ni-MH battery with a heater that withstands -40°C temperature" exhibited by FDK ("2HR" refers to the number of cells).


Use of Ni-MH batteries

Panasonic 12V energy regeneration system  Panasonic has begun supplying its "12V energy regeneration system" using nickel-MH batteries for Nissan's Dayz Roox and Mitsubishi Motors' eK Space that were launched in February 2014. The system is referred to as "pre-stop start-stop & battery assist" by Nissan, and as "auto stop & go (with coasting stop function)/assist battery" by Mitsubishi Motors.
 The system is designed as a 12V system to match the voltage of the lead-acid batteries. It can therefore be integrated with the conventional start-stop system without using a transformer. The use of Ni-MH battery with higher temperature characteristics simplifies the control and cooling system.
  For the "12V energy regeneration system," the company decided to combine Ni-MH battery with a lead-acid battery which is developed for start-stop system, since the battery is subject to harsh conditions on vehicles with a start-stop system.
FDK Batteries for eCall, eToll  The company's Ni-MH batteries are supplied to European markets as power supply for "eCall" (emergency call) and "eToll" (toll collection) services. The conventional product works at temperatures as low as -20oC. To meet a market request, FDK has developed a new product with an integral heater for use in -40oC environment.



Lead-acid batteries for start-stop systems

 Shin-Kobe Electric Machinery and Furukawa Battery each exhibited lead-acid batteries for start-stop systems. Weaknesses of lead-acid batteries, such as the low input characteristics and short cycle life, have been reinforced. Furukawa Battery's UltraBattery adopts a new technology characterized by a fusion of functions of lead-acid batteries and capacitors.


TuflongECO-IS "Batteries for start-stop systems" (TuflongECO-IS) exhibited by Shin-Kobe Electric Machinery ("Q-85" for Toyota Vitz/Nissan March-class vehicles on the right, and "M-42" for mini-vehicles on the left) UltraBattery "Batteries for start-stop systems" (UltraBattery) exhibited by Furukawa Battery


Lead-acid batteries for hybrid vehicles and vehicles with start-stop systems

Shin-Kobe Electric Machinery Auxiliary Automotive Battery for Hybrid Vehicles  On hybrid vehicles, the 12V battery is usually confined in an inaccessible space. Shin-Kobe Electric Machinery exhibited the maintenance-free Valve Regulated Lead Acid battery that does not require constant replenishment of water. This battery has warranty for 24 months or 30,000km on odometer and is used in Toyota Aqua, Prius, Prius α and Prius PHV. It is not used for starting the engine. The battery is marketed under the trade name of "TuflongHV."
 In the VRLA battery, the oxygen gas generated at the positive plates during a charging process is recombined with hydrogen at the negative plates and restored to water. This prevents loss of the electrolytic fluid (diluted sulfuric acid).
Automotive Batteries for Start-Stop System  The lead-acid battery for start-stop systems represents a number of technical improvements; higher performance resulting from a low-resistance structure (low-resistance positive plates, high-input negative plates), longer cycle life resulting from the use of high-density active material (more than 3-folds longer than conventional products), and higher input performance resulting from the use of new additives (more than 1.5-folds higher than conventional products). The battery is marketed under the trade name of "Tuflong ECO-IS."
Furukawa Battery Automotive Batteries for Start-Stop System  Furukawa Battery's "UltraBattery" for start-stop systems has positive plates that are made of lead dioxide as in conventional lead-acid batteries. Its negative plates are made of lead wrapped by a capacitor layer. The combined functions of lead-acid batteries and capacitors doubles the battery life. The "UltraBattery" has warranty for 36 months or 60,000km, the longest warranty among Japanese battery manufacturers.
 The capacitor layer increases the battery's charge acceptance, and increases the speed of recovery of charged state after discharge by 30 percent. The battery therefore is ideal for frequent stop and restart cycles of the engine.
 The improved charge acceptance helps to suppress the degradation known as sulfation (in which the process of lead sulfate reverting to lead at the negative plates slows down). This has nearly doubled the life cycle of the battery.

(Note) Panasonic, GS Yuasa and other lead-acid battery manufacturers have also developed and are selling lead-acid batteries for use in start-stop systems.

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