Batteries


A battery or cell is a source of electrical energy. It is a galvanic cell where the chemical energy of the redox reaction is converted into electrical energy. it may have one or more than one cell connected in series or parallel based on output performance requirements. For general purpose use, it should be lightweight and compact in size at the same time it should have a stable output voltage(very less variation in output voltage).

1.1 Primary Batteries

Primary batteries are batteries in which the redox reaction occurs only once and after significant period of time battery becomes useless and cannot be reused again. A dry cell or Leclanche cell is one such example of a primary battery. 


Construction:
1. A zinc container ( also acting as anode)

2. A Graphite (acting as a cathode) surrounded by powdered manganese dioxide and carbon

3. Ammonium chloride (NH4Cl) and zinc chloride (ZnCl2) paste filling the entire volume


Working:

Redox reactions that take place are:

1 At anode side : 

2.At cathode side : 


This cell has a potential of 1.5 V. (approx)


1.2 Secondary Batteries

A secondary cell is a cell which can be used again and again. It can be recharged by passing current through it in the opposite direction. Normally it can undergo a large number of discharging and charging cycles.

A simplest example is a lead storage battery.It is most commonly used in automobiles and invertor applications.




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