What is Battery-Definition,Types/2021

What is Battery for Students and Children-Basic Knowledge

Definition of Battery

A battery is an electrochemical device that converts chemical energy into electrical energy. It is a combination of two or groups of cells. One of the main advantages of a battery is that it stores energy. A battery may be non-chargeable or rechargeable. Non- Chargeable battery is known as a primary battery and a chargeable battery is known as a secondary battery.

Example-Lead acid batteries, nickel-iron cell/batteries, cadmium batteries, etc.

A battery is a combination of cells. So let us study cells.


A cell is nothing but a single unit and its process is the same as in a battery. It also converts chemical energy into electrical energy. It gives minimum supply voltage. The maximum voltage is 1.5 v to 3 v.

what is battery

Example-cells used in watches, remote control, lamp, clock

Difference between Battery and Cell:-

Battery Cell
1. A battery is a group of two or more two cells. Overall, it is a collection of cells that can be either connected in series or parallel.1. A cell is a single unit.
2. It stores chemical energy and converts stored chemical energy into electrical energy.2. It also stores chemical energy and converts chemical energy into electrical energy
3. A battery has either primary or secondary cells or whether it is non-rechargeable or rechargeable3. A cell is either wet or dry type depending on what electrolyte is used. It can use a single time.
4. A complete storage battery is a combination of cells so it is bigger in size and bulky4. As a cell is a single unit, it is light in weight.
5. A battery can supply power for a long duration5. A cell supplies power for a short duration of time.
6. A battery is mostly used in heavy-duty. It is used in industry for back power as UPS, inverters in households, automobiles, etc6. A cell is used in light loads that require less energy. It is used in watches, torches, clocks, lamps, etc
7. A battery is much more costly7. A cell is cheap in cost


Both in battery or cell, the process is the same and inside it, the phenomenon occurs due to the decomposition of chemical used as electrolyte. So electrolysis can be defined as the chemical decomposition which occurs in electrolysis when an electric current passes through them.

Some important terms used in electrolysis:-


An anode is related to the term in which the plate or electrode is connected to the positive terminal of supply. In other words, an anode is defined as the plate or electrode through which the current enters the electrolyte is known as the anode.


A cathode is defined as the plate or electrode through which the current liberated the electrolyte is known as cathode. In other words, the cathode may be defined as the plate or electrode which is connected to the negative terminal of the supply.


This phenomenon is seen in electrolysis as when current flows through the electrolyte, the electrolyte gets chemically decomposed. This decomposition is split up molecules into two parts known as ions.

These ions are further divided into two parts known as cations and anions.


Ions having a positive charge are known as cation


Ions having negative charges are known as anions.

Electromotive force (emf) of a cell (E)

When the circuit is open then the potential difference between the positive (+ve) and negative plates (-ve) of a battery is called as emf of a battery. It is denoted by E.

A terminal voltage or potential difference of a cell (V)

When the circuit is closed then the potential difference between plates of a positive and negative terminal which causes current flow through the external circuit is called terminal voltage (V).

What is the internal resistance of a cell?

When the electrodes of a battery are connected through an external circuit or load then current not only flows through the external circuit but also flows inside the cells of the battery to complete the circuit. As the current flows through the cell, the electrolyte offers some resistance to the flow of electricity. This is called the internal resistance of a cell.

It depends on the size and spacing of plates and is independent of the current delivered by the cell.

When the size of the plate increases the internal resistance decreases.

If the spacing between plates decreases the internal resistance decreases.

Cells connected in series:-

Consider there are a number of cells having emf E1, E2, E3….., Internal resistance of cells are r1,r2,r3,…, cells are connected through an external circuit is R, and a current flowing through the circuit is I


The total emf of the cells is nE, the Total internal resistance is nr then the resultant current flowing is

I=Total emf/total resistance= nE /(R+nr)

Cells connected in parallel

If m similar cells are connected in parallel then total emf =E, as in parallel emf is the same i.e. E

I=E /(r/m) +R= mE /(r+mR)

A mixed combination of the cells

I=nE/R+ (nr/m) =m nE/ (m r+n r), for maximum current m R=n r

Types of Battery and Applications

Basically, batteries can be divided into two parts primary cell or primary battery and secondary cell or secondary battery. But depending on the application they are further divided into

1. Used in Households:batteries are used as cameras, torches, clocks, remote control, mobiles, etc. These are further subdivided into:-

(a) Rechargeable:-nickel-iron cell, Cadmium battery, lithium-ion cell

(b) Non-rechargeable:-zinc-carbon cells, silver oxide, and alkaline these come under dry cells.

2. Industrial batteries:these batteries are used for heavy-duty. These are used as backup power in case of ac supply fails.

Nickel iron and Wet cadmium (Ni-Cd) under this category

3. Used in Vehicles:Lead-acid battery is mostly used for this purpose. These batteries are used to power vehicles, buses, cars, boats,s, etc.

Lead-acid batteries are used in the industry for diesel generators and other purposes.

Lead-acid battery

A lead-acid battery comes under the category of a secondary battery. It is rechargeable. A complete storage battery is a combination of cells. Each cell consists of a number of plates having positive and negative plates. All positive plates are soldered to one terminal known as a positive terminal and all negative plates are soldered to another terminal known as a positive terminal.

what is battery

They are assembled so that each positive plate is interlinked between negative plates. As the negative and positive plates are kept very close to each other, there are chances of an increasing tendency of short circuits. For avoiding short circuits wooden, glass, or rubber are used as separators between each positive and negative plate.

Internal short circuits may also occur due to the accumulation of active material at the bottom of the cells. To avoid this considerable space is allowed between plates.

For lead-acid cell electrolyte used is a dilute solution of sulphuric acid. In a lead-acid battery, three parts of water to one part of sulphuric acid are used.

Some standard data for lead-acid cell

  1. The specific gravity of the initial charge of the cell is 1250.
  2. When the cell is fully charged specific gravity of the cell is from 1260 to 1280.
  3. On load, when a cell is discharged, the voltage is 1.9 V
  4. On load, the fully charged cell has a voltage of 2.1 V

The specific gravity of a battery is measured by Hydrometer .

During charging

  1. It becomes dark chocolate brown in color (PbO2) at the anode and the cathode terminal becomes a grey lead metallic lead.
  2. Due to the consumption of water, the specific gravity of sulphuric acid (H2SO4) is increased
  3. Voltage increased
  4. Energy is absorbed.

During discharging

  1. Both anode and cathode become lead sulfate (PbSO4) which is whitish in color
  2. Due to the formation of water, the specific gravity of the acid decreased.
  3. The voltage of the cell decreases.
  4. Energy is released from the cell.

Care should be taken while using a lead-acid battery

  1. Must not keep it in discharged condition for a long time.
  2. Must maintain the level of electrolyte and it should always be 2 cm above the top of the plate in each cell.
  3. Add distilled water from time to time so that the evaporation of electrolytes should be compensated.
  4. It must be kept in clean and dry condition.
  5. During charging keep the vent plug in loose condition for passing out of the evolved gases, if any.
  6. Do not use naked flame near the battery it must be avoided.


Both have capacities measured in ampere-hours (Ah).

Meaning of Ah

It represents the current released or drawn during discharging or charging at a certain time.

Let us understand it

Suppose the load is connected to the battery having a full load is 50 amperes and a battery capacity is a 100-ampere hour (Ah). It means its charging and discharging time is 2 hours.

Or, 100 Ah =50 amp x h

Or h= 100/50=2 Hours


Ampere hour efficiency= (Rate of discharging current/Rate of charging current) X 100


AH efficiency= (amp. hrs on discharge /amp.hrs. on charge) x 100

Its efficiency normally lies between 90 to 95 %.


Battery and cells are mostly used today in every task. These play a vital role in Households, Industries, automobiles, etc. These are some of the most inventions for human life.

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