The capacitor can not act as a battery because capacitors discharge quickly whereas batteries discharge slowly. In this article, we will understand why can’t a capacitor act as a battery.
Capacitor and Battery are considered electronic devices that store potential energy and releases it when required. We will first look into the major differences that set these two devices apart and also look into the importance of each device based on their functionality, voltage values, charging capacity, cost, sizes, and types. But before that, let’s look into the basics of each of the two devices in the first two sections.
What is a Capacitor?
A capacitor is a passive electronic device that is used to store or release the potential energy that it takes from the electric circuit. This potential or electric energy is stored in the electric field around it. It does not drive or generate electric current or power in the circuit, it can only absorb or release the power in an electric or magnetic field. A capacitor does not require any power to be supplied to it in order to operate, as it is a passive device that provides no amplification or gains to the circuit. A capacitor is constructed by placing two metal plates facing parallel to each other, with a dielectric medium like air, ceramic, plastic, glass, oxide layers, etc.
The capacitor operates by charging and discharging the electric charge or voltage stored in the form of electric energy in its electrostatic field. The capacitor plates store the energy by attracting opposite chargers in the pair of parallel plates during the charging phase, resulting in a voltage spike. But during the discharging process, the electric charges are released, and thus the voltage at the capacitor drops.
What is a Battery?
A battery is an active electronic device that is used for storing chemical energy and then converting it into electrical energy to be supplied as power or current to drive or operate various electronic components in the circuit. A Battery is comprised of three important parts namely – the positive terminal (i.e. the anode), the negative terminal (i.e. the cathode), and an ionized fluid or substance called an electrolyte, which acts as a medium for the flow of electric charges within the battery. Unlike a capacitor, a battery is an active device that generates power and drives the flow of electric charges or current in the circuit.
The battery operates by producing electricity or flow of current in the electronic circuit by means of a chemical reaction called oxidation and reduction reactions that are responsible for generating electrons and driving their movement across the ionized fluid called an electrolyte. The electrons and protons move to electrodes cathode and anode respectively, during the charging and discharging phases, which results in the conversion of chemical energy stored in the battery into electrical energy.
Reasons for capacitor can not function as a battery
The difference between the capacitor and battery is mentioned in the below table. If you see the features of the capacitor and battery, we can not use a capacitor as a battery.
Difference between Capacitor and Battery
The comparison table given below highlights all the key differences between a capacitor and a battery –
| Parameter | Capacitor | Battery |
| Definition | A capacitor is a passive device that only stores and dissipates electric energy in the electric field. | A battery is an active device that converts the chemical energy stored inside it into electric energy to be used by other electronic components in the circuit. |
| Construction | A capacitor is made up of two metallic plates placed parallel to each other with insulating material between them called the dielectric material. | The battery is comprised of three parts namely – cathode, anode, and electrolyte. |
| Working Principle | The capacitor operates on the basis of the electrostatic mechanism, according to which, the capacitor begins storing electric charge in its electric field when it is charged with voltage. | Battery functions based on the oxidation-reduction reaction, that occur during the charging and discharging phases of the circuit, to produce a power supply or electric current to drive the circuit operation. |
| Active/Passive Device | A capacitor is a passive device as it can only store energy in its electrostatic field but cannot produce or generate power or electric current in the circuit. | A battery is an active device as it has the ability to generate electric current flow in the circuit and can also store electric energy. |
| AC and DC Power Affects | A capacitor has the ability to allow the flow of alternating current (AC), but it prohibits the flow of direct current (DC) through it. | A battery can only produce and store direct current (DC). It can neither generate nor take in an alternating power supply. |
| Types | Capacitors can be of different types such as supercapacitors, hybrid capacitors, mica capacitors, ceramic capacitors, etc. | A battery can also be of several types based on its chemical composition such as Nickel metal hybrid battery, Lithium battery, Alkaline battery, Nickel-cadmium battery, etc. |
| Voltage Variations | The voltage across the capacitor increases dramatically during charging and drops rapidly during the discharging phase. | The voltage across the battery remains constant during the discharging process. |
| Density of Energy | The capacitor has comparatively lower energy density as compared to a battery. | The battery has comparatively higher energy density as compared to a capacitor. |
| Polarity of the Device Ends | The polarity of the capacitor plates remains the same during the charging and discharging mechanisms. | The polarity of the battery terminals reverses in the charging and discharging mechanisms. |
| Charging and Discharging Duration | The speed at which the capacitor discharges is very fast, i.e. it takes about 1 to 10 seconds on average. | The speed at which the battery discharges is very slow i.e., it takes on an average of about 20 minutes to 1 hour. |
| Lifespan | The time for which a capacitor lasts or operates is longer than that of a battery, i.e. ranging between 10 to 15 years. | The time for which a battery lasts or operates is shorter than that of a capacitor, i.e., ranging between 5 to 10 years. |
| Expense | The cost of a capacitor is comparatively lesser as compared to that of a battery | A battery is relatively more expensive than a capacitor |
| Applications | Capacitors find their applications in storing memories in large computers, filters, power factor correction, etc. | A battery is used as the main power-generating source to drive various electronic devices such as torches, toys, electric vehicles, etc. |
Can a Capacitor act as a Battery? The answer is No. The reasons for this are very clear in the above table.
Conclusion
In conclusion, both capacitors and batteries are electronic devices that store electric charge in different forms. But besides this, there exist several differences between these two devices such as their working principle, construction, expense, and applications that set them apart. The most prominent difference between them is that a capacitor is a passive device that only stores electric charge, while a battery is an active device that stores and generates electric power to drive the circuit operation.
Looking at the above differences in the construction and applications, the answer to whether a capacitor can act as a battery is a big no.
Thus a normal capacitor can not act as a batter. Yes , a specially developed super capacitor can store the large amount of charge and discharges slowly. It can act as a battery. The more research is going on in the field of super capacitors.