What makes Power Capacitors safer and more reliable than ever?

Safety of a system comes in layers. If a safety issue exist, then it has to be addressed at multiple levels. The first level is prevention, i.e. make sure by design or by technology choice that the safety risk doesn’t exist at all. This is the level where power capacitors offers intrinsic safety and reliability. Nevertheless, power capacitor battery packs can store and release enormous amounts of electric energy. Just like with any such system, general principles of safety with power electricity still apply. Let’s now focus on the inherent safety of the technology:

Electrolyte: while the power capacitors contain a small amount of electrolyte, its purpose is mainly to act as a filler and as a pathway for the charges to move. The electrolyte is soaked up by the nano-carbon material, so that even when the cell’s skin is breached, very little or none will leak out.

Use of Nickel and Cobalt. These metals offer a trade-off between energy and power density. More Nickel means more energy, more cobalt means more stability. The 18650 cells contain no Nickel but provide the highest power density. The metal are only present on one electrode and bounded in specific compounds so that no free metal ions can create dangerous dendrites.

The power capacitors come in different variants that reflect the dominant lithium battery technologies. This provides a trade-off between price, safety, reliability and performance but as it still functions as a capacitor, the electric energy is stored as electric charges with no active chemical reactions involved.

The nano-carbon materials increase the surface of the electrodes and hence increase the capacitance, allowing to store as much energy as traditional lithium battery cells.

Fault tolerant, resilient power pack batteries. The powerpack is created by connecting the capacitors is a small grid mesh. If for some reason a cell would become defective (e.g. because it is damaged), then the electrolyte that doesn’t get soaked up by the carbon material might leak out and will evaporate. As no dendrites can form to create a short circuit between the electrodes, the above failure mode becomes an open circuit and while the power pack will loose some capacitance, it will continue to function as a battery.

No dramatic warming up: as each cell has a low internal resistance and in combination with the meshing connections, a power capacitor pack warms up very little even when high currents are used.

Destructive tests have demonstrated the safety of the cells: short circuit, overcharging, forced discharging, fire, drop test, nail puncture (internal short circuit), even shooting on it with a gun showed no fire and no explosion.

Our stress and abuse tests have demonstrated extreme robustness. Even when subjected to load conditions way beyond the permissible values, the cell keeps functioning. See the results at https://kurt.energy/unparalleled-robustness-of-blue-cell-power-capacitors/

Besides the safety and reliability benefits using power capacitors also translates into a simpler system design. Firstly, no BMS (Battery Management System) is needed to actively balance the cells when charging or discharging. A failing BMS is often a root cause for a battery fire. Secondly, as the cells operate from very cold freezing temperatures to very warm desert like temperatures, most of the no active cooling is needed as the cells barely warm up. Hence, most of the space is occupied by the cells and not by supporting subsystems.

While we currently mostly sell custom made power capacitor battery packs, production licenses can be negotiated.

The interested reader can find a very detailed overview of battery safety issues in the excellent special article of Best Magazine UK (url: https://www.bestmag.co.uk/emags/BESTMAG65-Summer2019/?page=39

A relevant extract can be downloaded here: BestMagAug2019 safety extract