How does an electrolytic
capacitor work?

Elko , E-Cap

Structure & function of an eCap

  • Voltage
  • Capacistance
  • Types
  • Service life
Definition of "electric capacitance"

Electrolytic capacitors belong to the group of electro-chemical capacitors. As is the case for all capacitors, the capacitance increases with the value of the electrode surface A and the dielectric constant ε and decreases with a higher distance of d.

ULTRACAPs are related to electrolytic capacitors much like cousins in a family. They are similar in principle, but in many aspects they are very different. Due to their higher insulation resistance, polarised electrolytic capacitors can reach voltage values of several hundred volts, although the capacitance of ULTRACAPs is millions of times bigger. Unlike ULTRACAPs, electrolytic capacitors are destroyed (burst) immediately if their polarity is reversed.

A large surface equals large specific capacitance

Anode metal is the basic material used for electrolytic capacitors, which consists of aluminium foil or a polymer in aluminium electrolytic capacitors. Both form a roughened anode, with a significantly larger surface area than a smooth surface would have. This increased surface area is an important factor in the relatively high specific capacitance of electrolytic capacitors compared to other capacitor families. Due to the high dielectric strength of the oxidation layer, the dielectric can be extremely thin. This very thin layer is the second important factor for the relatively high specific capacitance of the electrolytic capacitors.


Multiple quality features of electrolytic capacitors

The basic technology of electrolytic capacitors has been known for decades. A detailed description is given in Wikipedia. It should be borne in mind, however, that an incredible amount of expertise has gone into the development of these complex components. Developers are often surprised to find that a circuit has suddenly stopped working after a few months and the electrolytic capacitor no longer does what it’s supposed to. One of the reasons for this could be that the capacitor has dried out, which dramatically reduces the capacitance. Incorrect formation during production can also cause problems.

In fact, there are a large number of factors affecting quality and value for money that can accidentally be overlooked. One thing is clear: complex electrical assemblies can only be developed and marketed successfully if customers can be sure that dependable technology is used and manufacturing is performed to strict quality standards. And this is the case with our technology partner and manufacturer AiSHi.


The capacitance of a capacitor is specified in Farad (F) (named after Michael Faraday).  A capacitor has the capacistance of 1F when it is charged to 1V in 1s with a current of 1A.

            1 F 1 As/V   or  1 Farad = 1 ampere second per volt.

The stored energy (work W) of a capacitor results from:
             W = 1/2 C U2
The usable energy is derived from the voltage difference at the capacitor in accordance with the following formula:
             Wusable = 1/2 C (U2max - U2min)