Cell is an active device which can produce electric current by chemical reaction and vice-versa. A number of a cell arranged in a series or parallel manner is known as a battery. Cells are classified into two categories:
A primary cell is a device in which the chemical reaction isn’t reversible. The chemical reaction is needed for producing an electromotive force and thus delivering the current to the load circuit. During the working of the cells, one or more elements or constituents of the cell are being wasted. After that, the cell can’t be used further. it has a low value of efficiency. Two main defects occur in this type of cells, such as local action and polarisation.
In this category of the cell, we get the Daniell cell, Weston cell, Voltaic cell, Leclanche cell etc. The maintenance cost of this type of cell is very low. The primary cell is of low cost, low eff & low amp-hr capacity. The life of the cell constituents is completely eaten up the formation of plates isn’t necessary.
A secondary cell is a device in which the chemical reaction is made reversible by choosing suitable chemicals. In this type of cell, electrical energy can be stored in the form of chemical energy, which can be converted into electrical energy when required. In this type of cell, the efficiency is high and local action is only the defect. In this category, we get lead-acid cells and alkali cells.
The maintenance cost is also very high. The secondary cell is of higher cost, high efficiency and high amp-hr capacity. Formation of the plates is essential. A lead-acid cell has a life of about 1000-1200 charges and discharges & an alkali cell has a life of about 5 years.