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Capacitor maker Ioxus announced today that it has raised $21 million to ramp up development and production of ultracapacitors — a nascent battery space that could more useful than traditional batteries in electric cars.

Ultracapacitors can reach a much higher charge and discharge rate when compared to typical batteries. They also have longer lifetimes that last several hundreds of thousands of charge cycles when compared to normal batteries. But they do not carry as much energy per battery weight as typical lithium-ion batteries in electric cars right now, which would lower the net range of the car.

That would make them viable in electric sport and super cars like the Tesla Roadster, where power is more important than range. But they are less viable in more mass-appeal electric vehicles like the Nissan Leaf, which are trying to basically replace the internal combustion engine car but suffer from shorter ranges and limited fueling stations.

They can also be useful in micro-hybrid cars, which use internal combustion engines that turn off when the car comes to a stop and turn back on when they accelerate. That eliminates the fuel spent and emissions when the car is idling. Ultracapacitors can also charge up quickly with bits of energy from solar and wind power sources, and discharge it across a power grid when traditional power sources fail or when the grid finds itself under additional strain.

The company raised the funding from Energy Technology Ventures, a joint-venture between General Electric, NRG Energy and ConocoPhillips. Northwater Capital, Aster Capital and Braemer Energy Ventures also participated in the most recent round of funding.


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