A battery is a device which stores energy in a chemical form, and converts it into electrical energy when it is connected to a circuit. The most basic way to do this is to simply connect a conductive wire between the positive and negative terminals of the battery; this will produce a steady stream of electrons (called a current) through the wire from the chemical reaction in the battery. Before we get to deep into how a battery is made, there are a few definitions that may help you understand the concepts behind batteries.

Batteries and Cells

Technically, a 'Battery' is a collection of 'Cells' connected together to obtain a higher voltage. Something like your standard AA battery is really a 'Cell' (a single electrochemical cell). In common language, even a single cell is however referred to as a battery. The operation of a battery is best understood by looking at looking at what goes on inside an electrochemical cell. The rest of the information in this section will be related to the operation of an electrochemical cell.

An Electrochemical Cell

An electrochemical cell consists of two terminals (or electrodes) suspended in an electrolyte. The terminals are called the anode (-) and the cathode (+).

Terminals (or electrodes): is a conducting material which is used to make contact with a non-metallic part of a circuit (in a cell, the chemical in the cell).

Electrolyte: is a liquid which conducts electricity by allowing charged ions to mover inside it. It also acts as an insulator between the two electrodes to avoid an internal short circuit.

Atoms and Ions

Every atom consists of a very small 'Positively' charged nucleus surrounded by a number of even smaller, 'Negatively' charged particles called electrons. Each of these electrons carry the same amount of 'Negative' charge, and the charge present on the nucleus is equal in size to the total charge of all the electrons in an atom; Atoms therefore, have a neutral charge overall. Atoms become positively or negatively charged by either gaining or loosing electrons, in this case, atoms become ions.

There are a number of different shapes and sizes of battery; here is a list below of the various types:

Cylindrical Cells
Button Cells
Coin Cells
Battery Packs

Example of the build process

Different chemistries, manufacturers and cell sizes determine the way in which a cell is constructed; for ease of description, the following example is of how a standard alkaline (manganese dioxide) cylindrical bobbin cell is made.

Like all cells, alkaline cells contain a cathode, anode and an electrolyte. The cathode is on the outside portion of the cell, and the anode is on the inside portion.

Firstly the steel can casing for the battery is constructed; it is nickel-plated and the inside of the can is coated with a layer of carbon which acts as a contact between the positive pole (cathode) and enables smooth flow of electrons through the battery. The preformed top in the bottom of the can serves as the positive contact.

The cathode is a mixture of manganese dioxide, graphite and an electrolyte. The first process in the manufacture of the battery is to granulate this mixture, leave it to age, and then compact it into a pressed tablet assembly.

These tablets are then inserted into the steel can and become the cathode of the battery. An indentation/grove is made near the top of the steel can and the sealant is placed just above it to protect the battery from leakage.
A special paper soaked in an electrolyte is then inserted into the can to stop the anode and cathode of the battery coming into contact with one another. When the battery is connected, the electrons re-enter the battery and merge with the cathode material. The thus formed ions will then be transported back to the anode, through the separator paper.
The anode is now inserted; the anode is a gel made up of mostly zinc powder and several other materials. This gel is inserted into the steel can against the separator paper.
The battery is then sealed; the seal is made up of a brass pin/nail which acts as the current collector, this leads the electrons from the anode to the external flow. A safety valve (a plastic gasket) is placed above the bottom plate. A steal washer and a metal end cap are the inserted against the indentation formed earlier. The battery is then closed by means of curling the steel can around the items above.
The battery will then be wrapped in a PVC foil with the companies design printed on it. The battery will then be tested and stored in a warehouse ready for packaging or dispatch.