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Ioxus Developing Higher Power Density Ultracapacitors

Ioxus, a young (2006) ultracapacitor spin-off from Custom Electronics, an established supplier of high-reliability capacitors to commercial and military clients since 1964, is targeting the development of higher power density, compact ultracapacitors, applied in a full range of applications spanning military, industrial and automotive needs. (Earlier post.)

Typical ultracapacitors are characterized by high power density compared to batteries (but poor energy density), as well as quick charge and discharge. Ioxus says that the power density of its 100F carbon-carbon ultracapacitor solutions is 2x over that of competitive comparable 100F cells. On the larger cells, such as the 2000F, Ioxus offers 20% more power than Ness, is at parity with Maxwell, and is higher in volumetric density, according to the company.

Ioxus expects a new set of cells, targeted for release at the end of the year with different terminations, to surpass Maxwell’s large cells in both volumetric and gravimetric power densities.

Smaller Ioxus cells offer a power density of 22-28 kW/kg, and larger cells offer densities of 12-15 kW/kg, said Chad Hall, COO of Ioxus. Energy densities for the cells are typically around 2-4 Wh/kg. Ioxus says that it is working on increasing the energy densities as well.

Ioxus makes carbon-carbon ultracapacitors—i.e., both electrodes are carbon, as opposed to the hybrid (asymmetric) ultracapacitors in which in one of the electrodes is carbon and the other electrode utilizes a different material. Energy densities of hybrid ultracapacitors can be significantly greater than that of carbon-carbon ultracapacitors, but power densities are lower.

To achieve its power densities, Ioxus says that it essentially uses multiple types of carbon to pack the material as best as possible and a variety of different types of carbon with different conductive properties. Ioxus has also optimized binders to adhere to special foils, Hall said. The packaging of the cell is also a factor, he noted. (Ioxus offers a prismatic ultracapacitor as well as cylindrical.)

Ioxus has filed 12 patents, with others under preparation.

Like its competition, Ioxus is interested in transportation applications—mass transit, hybrid-electric, train/light rail, and stop/start applications—sometimes in cooperation with a battery, depending upon the application requirements.

With its compact, high power-density cells, Ioxus is also interested in applying ultracapacitor solutions at different points of use in a vehicle—for example, replacing power steering with electric steering using ultracapacitors. Other potential applications include smart airbags, instrument clusters, multimedia/telematics, seatbelt releases, and power seats, locks and windows. Another application could provide “instant heat” to heat up the catalytic converters in vehicles.

Ioxus is also interested in working with battery companies on integrated solutions.

Two lithium-ion battery companies are working with us now. We’d like to see the ultracapacitors integrated into the battery—two separate chemistries integrated into the pack—so that the customer sees only two terminals.

—Chad Hall

As Ioxus moves forward with commercialization, it will produce modules for customers as well, first standard modules and then customized modules. The company has already designed an integrated ultracapacitor module to provide regenerative power assistance in retrofitting lead-acid battery powered forklifts.

According to Hall, one materials handling equipment manufacturer is projecting a purchase of up to 250 of the 36V, 450-Farad (10kW) EDLC Energy Reservoir System, or “EERS” modules. Each ultracapacitor module incorporates sixty 1,700F cells, control electronics, safety circuitry, interconnects, and a safety enclosure to deliver a complete stand alone power assist module. The module is compact and can be installed in about an hour.

A forklift equipped with an EERS module will increase the useable time of the battery pack by 30% allowing an operator to complete a full eight hour shift on a single charge of the lead acid storage pack. The use of the module also prevents the battery from deep cycling, extending the life of the battery.

Preliminary data suggests battery life may be extended four to eight times as opposed to using the battery without the power assist module, according to Ioxus. The incorporation of the power assist module also allow the size of the battery pack to be reduced by as much as 15% if desired.

The Ioxus ultracapacitor-based EERS module is designed to have sufficient energy storage to aid the forklift when under load—more specifically the module aids the lead acid storage pack when lifting loads of 3,000 lbs. As the ultracapacitor provides the bulk of the power when the lift is raised, the life of the battery is increased.

Potential applications outside the transportation sector include power quality (e.g., utility grid stability; telecom support, factory UPS, fuel cell starting and load leveling) and renewable energy (wind mill pitch control; solar positioning; variable generation; energy dispatching; and wave energy).



I think most important ultracapacitor parameter for transport applications is energy density. To sutisfy 10 s power density demand would be enaugh 3 kg capacitor. But in that case energy of 12 Wh would be drained during first 0.2 second when power demand 100 kW. Energy demand for EV aplications could be in the range of 100-300 Wh.
Please, correct if I am wrong.


Its easy to calc. Take the wh and multiply by 360. So with 12 it would be 4320 watts of power for 10 seconds. So a 30 kg capcitor bank would supply 43.2 kw for 10 seconds.

But thats not actualy what they require. They only need a very short burst of power and then a sustained oomph of lesser power.. say .2 seconds of full power and .8 seconds of half power and 6 more of 1/10th capacity.


So you are saying that 30 kg would be enough. But that means that capacity for short burst can be over 450 kW ("Smaller Ioxus cells offer a power density of 22-28 kW/kg, and larger cells offer densities of 12-15 kW/kg, said Chad Hall, COO of Ioxus."). At first glance it looks perfect match 7 kg capacitor would provide that power and energy range.
100 kW motor for 0.2 second would need 100 000W*0,2s/3600s=5,5 W energy. For next 0.8 s - 11 W and next 6 s -13,5 W. In total 29 W.

So if energy density would be 4 Wh/kg - 7 kg is OK.


Yup basicaly as long as you dont need full power for all 10 seconds you realy dont wind up needed all that heavy a cap.


It's great to see any progress on supercaps. But unless I'm trying to put together a rail gun, then I would much rather see improvements in energy density than power density.
I think supercaps can play a big role in automotive applications by reducing the strain on battery packs and extending their life and incresing the efficiency of regen braking. But there is a ways to go in energy density and cost to make it practical.

Henry Gibson

The CISRO (Australia) super battery combines lead batteries with super caps and is well tested. Small high power low energy flywheels would be cheaper as in the Flydrid than super caps and would not require much different electronics. ..HG..

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