What is an electrochemical double layer capacitor (EDLC)?

Electrochemical double layer capacitors or EDLCs are also known as supercapacitors or ultracapacitors.

No chemical reaction occurs in these capacitors. They store the charge in an electrochemical double layer (known as the Helmholtz layer) where the positive and negative ions in the electrolyte move through the electric field to the corresponding electrode. Because of their lower level of heat generation and longer lifetime, they are more resistant to ageing than lead acid batteries.

EDLCs achieve very high capacitance values, but they are limited to a voltage of 2.7 V. This means that many capacitors have to be connected in series. EDLCs have an energy density around 40 times higher than electrolytic capacitors and are ideal for use as an energy source in buffer modules. Unlike lead acid batteries, they have a high lifetime expectancy similar to that of power supplies and therefore do not need to be replaced during the operating period.

Electrochemical double layer capacitors can be used without problems at temperatures as low as -40°C and, as a result, are ideal for outdoor applications. Because of their very low boiling point, their upper temperature limit is +65°C.