Difference Between a Battery and a Capacitor

byAbhishek Vaishnav

A battery or A Capacitor are both energy storage elements. But, they are indeed very different.

  1. A battery stores energy in form of chemical energy, where as the capacitor uses electrostatic field.
  2. A battery generally has a better energy density, which means you could store more energy per volume.
  3. Capacitors although are superior when it comes to internal resistance, which implies they can supply a lot more current, but for a shorter duration of time .
  4. A battery generally maintains a constant voltage across its terminals, the voltage goes down only when it is almost or completely discharged. where as in capacitor, the moment you start sourcing current, the voltage drops.
  5. A capacitor can be used for filtering applications.
  6. A battery ALWAYS has a polarity.
Battery 

  • Definition-
 Battery stores potential energy in the form of chemical energy which is later converted to the electric energy.
  • Construction-
 Battery has three parts known as Cathode (positive (+ve), Anode (Negative (-ve) and Separator (known as electrolyte).
  • Function-
Batteries provide energy to the connected circuits. i.e. Battery generates electrons and charge.
  • Working Principle-
Battery works based on chemical reaction called oxidation-reduction reaction.
  • Operation-
 Battery Generate Electrons.
  • Types-
Battery types are Alkaline, Lithium Cells, Silver Oxide Cells, Zinc Air Cells, Zinc Carbon, Lead Acid, Lithium Ion (Li-ion), Nickel Metal Hydride (Ni-MH), Nickel Cadmium (Ni-Cd) etc.
  • Type of Device-
Battery is an Active Component.
  • AC & DC Usage-
Battery is used to provide DC supply.
  • Voltage Behavior-
A battery provides almost constant voltage while discharging.
  • Potential Difference (P.d)-
Constant
  • Charging and Discharging-
The Charging and Discharging time of a Battery is slow i.e. 10 – 60+ minutes.

Capacitor

  • Definition-
A Capacitor stores the potential energy in the form of eclectic field (electrostatic field) and release to the circuit as electric energy.

  • Construction-
Capacitor is a simple two terminal device Terminals are metallic plates and there is a dielectric material (insulator) between them. .
  • Function-
Capacitors draw, store and release the energy. i.e. Capacitor only stores charged electrons.
  • Working Principle- 
When voltage applied across the capacitor terminals, It starts to store energy in it.
  • Operation-
Capacitor Store Electrons.
  • Types-
Electrolytic, Electrostatic, Electrostatic, Electrochemical, Super Capacitor, Hybrid Super Capacitors, Ceramic Capacitors, Film Capacitors, Tantalum, Integrated Capacitor.
  • Type of Device-
Capacitor is a Passive Component.
  • AC & DC Usage-
Capacitor blocks DC supply and pass the AC supply.
  • Voltage Behavior-
A Capacitor discharging voltage quickly decreased. i.e. discharge rate is very fast.
  • Potential Difference (P.d)-
Increases exponentially
  • Charging and Discharging-
Charging and Discharging time of a Capacitor is very fast i.e. 1-10 seconds.

Similarities:-
  1. Both the electrical components can generate potential difference across another electrical component say resistor.
  2. They are used to store energy which can be tapped by connecting them in a closed circuit.
Differences:-
  1. Potential difference generated by a battery is constant, whereas, that generated by a charged capacitor changes exponentially with time.
  2. Though both the components are used to store energy, they achieve it in different ways being, battery stores electrical energy in the form of chemical energy, whereas, a capacitor stores it in the form of magnetic field.
  3. While charging a battery the polarity of the circuit must be reverse of that while using it, whereas, while charging a capacitor the polarity must be the same as it should be while using it.


Battery is an active device, which provides power / energy to a circuit. Capacitor is a passive component. However both if these store energy. Let us compare their usage for energy storage.
Battery is an electrochemical device for energy storage. It uses electrical energy while charging for reactions in chemicals stored in it to form new chemicals. When discharging, the chemical reactions proceed in reverse direction. Both charge/ discharge processes involve chemical reactions, which take energy , and thus there is loss of energy in both operations . This energy usable is much below the energy spent in charging the battery. Conversion efficiency is thus lower than 90 per cent. Lead acid battery efficiency is typically 65 %, while Li-ion battery has conversion efficiency of 80 %.
Capacitor, on the other hand, stores energy in electric field as electric charge for a given voltage. Energy is absorbed as electrical energy, and when needed , is drawn as electrical energy. No conversion in other form of energy is involved. So efficiency of capacitor can go over 98 %. Supercapacitors thus store large amount of energy this way , with a round trip efficiency of over 98 percent.
One other major difference—
Battery voltage is more or less constant during its user from fully charged conditions till is ready to be charged again. Capacitor, since energy stored depends on voltage, will have its voltage going down as its energy is being used up. So while using ultracapacitors for energy, we have booster circuits which keep output voltage constant for load despite falling capacitor voltage.
Difference Between a Battery and a Capacitor






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