What are ultracapacitors?

ultracapacitorUltracapacitors are a novel energy storage technology that offer high power density, almost instant recharging and very long lifetimes. Ultracapacitors have been in development for well over a decade but the technology has developed rapidly in the recent years. This development has been driven by advances in nanomaterials, the electrification of infrastructure and industry and increased concerns around fuel efficiency. Ultracapacitors are now delivering significant economic benefits across a wide range of markets including motorsports, automotive, aerospace, heavy industry and transportation, and renewables and grid.

The benefits of ultracapacitors include:

  • very long lifetimes of up to 1 million charge cycles
  • low maintenance requirements
  • a wide range of operating temperatures, from -40 °C to 70 °C
  • up to 60 times the power density achieved by batteries
  • 30% more efficient than batteries
  • no harmful chemicals or toxic metals

The functions ultracapacitors provide include:

  • back-up power
  • regenerative power
  • burst power
  • quick charge
  • cold starting

Find out more about the applications for our ultracapacitors


How do ultracapacitors compare to batteries?

Ultracapacitors store energy in an electric field, rather than in a chemical reaction. This allows them to charge and discharge much faster than batteries. They can also survive up to a million charge and discharge cycles, offering much longer lifecycles. Ultracapacitors have little or no internal resistance (down to 0,12 mΩ), allowing them to work at close to 100% efficiency. They are also significantly lighter than batteries and generally don’t contain harmful chemicals or toxic metals.

Ultracapacitors are good partners for lithium-ion batteries and other high energy density storage technologies. With power density up to 60 times greater than batteries, they can be connected in parallel to create combined power supply units. Due to load leveling, the ultracapacitors can significantly expand battery life and improve safety. In an electric car, for example, an ultracapacitor can provide the power needed for acceleration, while a battery provides range and recharges the ultracapacitor between surges.

Comparison chart

What makes Skeleton Technologies’ ultracapacitors so competitive?

The secret to the outstanding performance of our SkelCap ultracapacitors lies in the use of patented nanoporous carbide-derived carbon (CDC), also known as curved graphene. CDC differs significantly from regular activated carbons, which are used by other ultracapacitor manufacturers. Featuring finely engineered, consistent pore size, this patented material guarantees a very large accessible surface area, and a perfect match for the electrolyte ions. This allows us to deliver twice as much energy storage capacity and five times higher power performance compared to other ultracapacitors. The high degree of purity of curved graphene also ensures up to two times higher current tolerance, and four times lower resistance.


The use of curved graphene is one of the key factors in achieving the superior energy density of our ultracapacitors. SkelCap ultracapacitors have up to two times higher energy density compared to even the most advanced devices produced by our competitors.


CDC boasts electrical conductivity that is almost seven times better than that of regular activated carbons. As a result, the power density of SkelCap ultracapacitors exceeds competitors’ products by a factor of five.


Lower internal resistance also results in significantly higher efficiency and up to five times less energy being lost as heat. This is also an advantage because cooling systems can be downsized or removed altogether.


CDC has a high chemical purity, which gives it a significant reliability advantage over activated carbons. The special purification and post-treatment procedures applied to the materials used in SkelCap ultracapacitors results in even longer lifetimes.