What are ultracapacitors?

Ultracapacitors, or supercapacitors as they are also known, are a novel energy storage technology that offers 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, heavy transportation, maritime, and renewables and grid.


Ultracapacitor supercapacitor

The benefits of ultracapacitors:

Very long lifetimes of more than 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

Ultracapacitors vs. batteries

Ultracapacitors store energy in an electric field, rather than in a chemical reaction, like batteries. This allows them to charge and discharge much faster than batteries. They can also survive more than a million charge and discharge cycles, offering much longer lifecycles. Ultracapacitors have very little 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.


Skeleton Technologies is the only manufacturer covering the full value chain


"Curved graphene"

At the heart of our ultracapacitors' performance advantage is Skeleton’s nanotechnology research into patented curved graphene. Curved graphene differs significantly from regular activated carbons, which are used by other ultracapacitor manufacturers. All competitors use organic pre-cursor materials, mostly carbon made from coconut, Skeleton is the only company to use an inorganic pre-cursor and has patented the synthesis process for the proprietary material. The use of curved graphene is one of the key factors in achieving the superior energy density of our ultracapacitors.

Skeleton Technologies has also achieved one of the lowest ESR (equivalent series resistance) levels on the market. This factor is crucial as it greatly increases the efficiency of the cells by reducing the amount of energy that is lost as heat. This is also an advantage because cooling systems can be downsized or removed altogether.

Download our whitepaper on ESR

Ultracapacitor Cells

Skeleton’s SkelCap ultracapacitor series is unique in the world of ultracapacitors, not only because of patented “curved graphene”, but also the benefits it gives our cells. No other product on the market has as high power and energy density as the SkelCap cells, which are the basis for our modules and energy storage systems and come in the industry-standard cylindrical form.

We also offer custom cells for highly specialized industries such as motorsports, defense, and aerospace. The prismatic form factor of our custom cells enables efficient use of space and they are ideally suited to environments that require robust and reliable ultracapacitors. Our custom cells offer industry-leading power and energy density in the smallest cell sizes on the market.

Industrial Modules

The strengths of the SkelCap ultracapacitors carry over to our SkelMod 170V 53F, 102V 88F, 51V 177F, and SkelStart ultracapacitor modules. The modules benefit from the versatility of ultracapacitors, which means that ultracapacitor modules are perfectly suited for an almost unlimited amount of different applications. The high power modules are suitable for example for heavy transportation, drivetrains, pulse power supply, Kinetic Energy Recovery systems, peak assistance, load leveling, UPS systems, and industrial applications.

Energy Storage Systems

Skeleton’s full energy storage systems, such as the Industrial UPS, are complete solutions for pain points that many of our customers have experienced. Our full systems include everything from the modules to the inverter, so that the only thing left for you is to enjoy the long lifetime and reliability of ultracapacitor-based energy storage systems.

What makes Skeleton's ultracapacitors so competitive?

Energy density

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.

Power density

Curved graphene 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 four.

Low Internal Resistance Means High Efficiency

The low internal resistance of our ultracapacitors 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.

Reliability and Long Lifetime

Curved graphene 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 result in even longer lifetimes.