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Ioxus introduces new iCAP ultracapacitor series with a 3,000F cell

The iCAP 3000F cells. Click to enlarge.

Ioxus, Inc. introduced its new iCAP 3,000 Farad (F) ultracapacitor, the first size in a new family of cell products. Rated at 2.7V (2.85V surge), the new iCAP represents the lowest weight, lowest equivalent series resistance (ESR) and highest power density currently available in the market for energy storage cells, the company says. They feature a cycle life of more than 1,000,000 cycles, rated to half rated voltage, 25 °C.

Ioxus is targeting a number of markets for the iCAP: transportation drives or systems (comprising several specific sub-groups, notes Chad Hall, Founder and VP Sales); grid power storage; large regenerative energy capture (e.g., for rubber tire gantry cranes in ports); backup power and uninterruptible power supply (UPS); power conditioning; and renewable energy systems.

Quick Specs
Capacitance (F) 3000
ESR, DC ≤(mΩ) [10ms] 0.26
ESR, AC 1kHz ≤(mΩ) 0.22
Inductance ±20(nH) 60
72hr Leakage ≤(mA) 5.0
Current, Peak [1s] (A) 2300
Continuous Current (A) 145
Resistance, Thermal (°C/W) 4
Emax (Wh) 3.04
Emax (Wh/kg) 6.0
Emax (Wh/L) 7.7
Pmax (kW/kg) 16.2
Pmax (kW/L) 20.9
Pd (kW/kg) 6.6

In all of these areas, the Ioxus iCAP 3,000F ultracapacitor delivers the heaviest duty cycles possible and the longest life, due to minimal temperature rise, the company claims. Further, Ioxus iCAP cells are designed for high shock and vibration applications such as heavy equipment or rail.

The iCAP series features the same electrochemistry as in the first-generation cell, Hall said, but Ioxus has significantly improved the packaging and the interfaces to generate the increase in power density over the earlier generation. Within the transportation applications, there are a number of specific applications of interest, Hall said:

  • Hybrid buses, using the ultracapacitors for energy capture and acceleration.

  • Light rail, for use either in smaller on-board APUs to handle ride-through (the switching between power stations on the rail), or on-board storage for acceleration.

    Ride-through applications require a high-cycle life; exchanges between stations occur typically about ever 50 meters, Hall said, with the lowering of power producing a detrimental effect on the train electronics over time without a bridging solution such as that provided by the ultracaps.

    On-board acceleration is seeing more demand in European countries as they try to put train stations in city centers without the use of catenary lines. They use the ultracaps to accelerate away form the station, and then once out a couple of thousand meters, switch over to electric or diesel power.

    Cooling requirements become a problem in these applications, Hall noted, and even a 5% reduction in ESR can make a big difference in cooling.

  • Start-stop for micro-hybrid applications. Low ESR ultracapacitors can go in series with existing batteries to provide robust support for the start-stop application. Although the ultracap unit would increase the cost of the system by about $100, Hall said, there are other savings inherent in not having to run an AGM lead-acid battery over a larger voltage cycle.

    Further, some start-stop systems suffer from lower charge acceptance in cold environments, or shut off entirely due to the battery limitations. The ultracapacitors, which have an operational range from -40 °C to 65 °C are not similarly limited.

    The ultracaps can also provide acceleration for a mild hybrid power application, with more efficiency and a smaller volume of required space than NiMH batteries, Hall suggested.

  • Material handling.

  • Cold starting for heavy-duty equipment.

As our customers in automotive, energy and other sectors push their offerings toward greater efficiency and higher performance, the importance of 3,000F ultracapacitor cells increases. By lowering the ESR, increasing the power density beyond the most competitive product available, and making the product rugged enough to pass shock and vibe tests that competing products cannot, the Ioxus iCAP series delivers what no one else can: a more powerful, more rugged cell that adapts to myriad uses.

—Mark McGough, CEO of Ioxus

The Ioxus iCAP 3,000F ultracapacitor allows 3 separate types of connections with one terminal set: welding, bolting, and press-on busbars. The cells are suited for prototype-to-production support, facilitating low ESR bus bar connections with the largest achievable contact areas. The double holes are off-axis, preventing cell damage during assembly and making the Ioxus iCAP 3,000F ultracapacitor durable enough for even the toughest applications.

Among the market differentiators of the Ioxus iCAP 3,000F ultracapacitor are:

  • Weldable, double female threaded terminals;
  • Largest diameter terminals;
  • Single terminal design for bolted or welded connection;
  • Lowest cell ESR; and
  • Mil-spec tumble test rated. (The tumble test drops cells randomly in a tumbling machine, 900 times in 45 minutes.)



A very rugged, long lasting, ultra quick charge, low energy density (6Wh/Kg) storage unit. Could complement and extend batteries life in Stop-Start and braking energy recovery units.


I've been a huge fan of ultracaps/supercaps for years. I'm very happy to see Ioxus at least keeping Maxwell honest, but this is the same specs that they've both had out for over 3 years.

They may have tweaked some packaging to make a *slight* difference, but these nearly identical specs have been available from Maxwell since 2008:

I'm still waiting to see who will be the first to release a "next generation" cap with at least double, if not triple this energy density.

Henry Gibson

Switched reluctance motors with flywheels could store as much energy per weight and not require multiple cells.

EFFPOWER and now Atraverda have bipolar lead batteries that have much more energy and require less electronics.

Most vehicles with stop and go travel can use hydraulics with lower costs and complexities. A compressed air tank store a lot of energy in comparison with the size of capacitors. Compressed air (nitrogen) tanks can be made very small and different sizes without a theoretical weight disadvantage, so they can be place anywhere. ..HG..



If they can add this to a stop start system for $100, I'm not sure that anything else is going to be much more cost effective.

In the end, companies will go with whatever is cheapest or their competitors will.

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