Capacitor battery developer Kurt Energy has outlined how it complements the inherent safety of its 18650Y and 21700Y hybrid power capacitors and provides protection against abuse and external causes of fire.

It uses a device it calls a CID, which interrupts the current when the cell pressure builds up too fast, typically at about 10 bar. When the CID triggers, a hybrid power capacitor becomes an open circuit. It also opens to release gas in a second step at about 20 bar.

While power capacitors are typically used in applications needing high power, the 18650Y and 21700Y have energy densities from 80 to 130 Wh/kg.