How is a capacitor different from a battery?

Batteries and condensers seem similar because they store and release electricity. However, there are key differences between them that affect their potential applications due to how they work differently.

A capacitor consists of two or more conductive plates separated by a dielectric. When an electric current enters the condenser, the dielectric stops the flow and accumulates a charge that is stored in an electric field between the plates. Each capacitor is designed to have a particular capacitance (energy storage). When a capacitor is connected to an external circuit, a current will discharge quickly.

In a supercapacitor, there is no dielectric between the plates; rather, there is an electrolyte and a thin insulator like cardboard or paper. When a current is introduced into the supercapacitor, the ions accumulate on each side of the insulator to generate a double charge layer. The supercapacitors are limited to low voltages, but at a very high capacitance, since a high voltage could decompose the electrolyte.


The different types of batteries are distinguished by their chemical composition. The chemical unit, called a cell, contains three main parts; a positive terminal called a cathode, a negative terminal called an anode and the electrolyte. The battery is charged and discharged through a chemical reaction that generates a voltage. The battery can provide a constant DC voltage. In rechargeable batteries, the chemical energy that is converted into electricity can be reversed by using external electrical power to restore the charge.

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