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.There are many types of batteries those we are used very widely.

A. Primary Cells

B. Secondary Cells

C. Fuel cells

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A. Primary cell :- primary cell are those becomes dead after some time, and

cannot be used again. Two common example of this types are 'dry and mercury'

cell.

1. Dry cell :- The dry cell, commonly used in transistors and clocks. It consists of 

a cylindrical zinc container which acts as the anode. These cells have voltage in

the range 1.25v to1.50v . However , they do not have a long life.

2. Mercury Cell :- this is a newer type of dry cell which has found use in low

current devices such as hearing aids and watches. These cells voltage 1.35v

throughout its life.

B. Secondary cell :-

1. Lead storage batteries :- This is one of the most common batteries used in the

generally used in the automobiles and investors. A 12v lead storage battery is

generally used which consists of 6 cell each producing 2v.

Note:- (1) in a automobile when it is running , electrical energy is produced in the

alternator which keeps on charging the battery

>Lithium batteries :- Now a days ,use of rechargable lithium batteries is

becomes more common because of their light weight.

C. Fuel cell :- this cell used as the primary source of electrical energy on the

appolo noon flights. The weight of the fuel sufficied . For example :- for 11 daysin space was approximantly 200 kg.

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Advantage of fuel cell :-

1. The continuous supply , such cells never becomes dead. Such is usually

operated at a temperature of 70-140 .

2. They do not cause any pollution problem unlike thermal plants which burn

fossi fuel like coal, gas, oil, etc.

3. The fuel cells are expected to have an efficiency of 100%

I think that Secondary and fuel are we have mostly used in daily life.

A mercury battery (also called mercuric oxide battery, or mercury cell) is a non-rechargeable electrochemical battery, a primary cell. Due to the content of  mercury, and theresulting environmental concerns, the sale of mercury batteries is banned in many countries.Both ANSI and IEC have withdrawn standards for mercury batteries. Mercury batteries weremade in button types for watches, hearing aids, and calculators, and in larger forms for other applications.

History

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The mercury oxide-zinc battery system was known more than 100 years ago [1]  but did not become widely used until 1942, when Samuel Ruben developed a balanced mercury cellwhich was useful for military applications such as metal detectors, munitions, and walkie-talkies.[2] The battery system had the advantages of long shelf life (to 10 years) and steadyvoltage output. After the Second World War the battery system was widely applied for small

electronic devices such as cardiac pacemakers and hearing aids. Mercury oxide batteries weremade in a range of sizes from miniature button cells used for  hearing aids and electric wristwatches, cylindrical types used for portable electronic apparatus, rectangular batteries usedfor transistor radios,[3] and large multicell packs used for industrial applications such as radioremote control for overhead crane systems. In the United States, mercury oxide batteries weremanufactured by the P. R. Mallory and Co Inc, (now Duracell), and Union CarbideCorporation (whose battery division is now called Energizer Holdings).

[edit] ChemistryMercury batteries use either pure mercuric oxide or a mix of mercuric oxide with manganesedioxide as the cathode. Mercuric oxide is a non-conductor so some graphite is mixed with it;

the graphite also helps prevent collection of mercury into large droplets. The anode is madeof zinc and separated from the cathode with a layer of paper or other porous material soakedwith electrolyte. During discharge, zinc oxidizes to zinc oxide and mercuric oxide getsreduced to elemental mercury. A little extra mercuric oxide is put into the cell to preventevolution of hydrogen gas at the end of life. Mercury batteries are very similar to silver-oxide

 batteries.[2]

The overall reaction is: [2]

Sodium hydroxide or  potassium hydroxide are used as an electrolyte. Sodium hydroxide cellshave nearly constant voltage at low discharge currents, making them ideal for  hearing aids,calculators, and electronic watches. Potassium hydroxide cells, in turn, provided constantvoltage at higher currents, making them suitable for applications requiring current surges, e.g.

 photographic cameras with flash, and watches with a backlight. Potassium hydroxide cellsalso have better performance at lower temperatures. Mercury cells have very long shelf life,up to 10 years.[2]

A different form of mercury battery uses mercuric oxide and cadmium. This has a muchlower terminal voltage around 0.9 volts and so has lower energy density, but it has anextended temperature range, in special designs up to 180 C.[2] A 12 volt battery of this typewas formerly used for residential smoke detectors, where the two-step voltage characteristicgave a useful warning for replacement. [4]

[edit] Electrical characteristicsMercury batteries using mercury( II) oxide cathode have a very flat discharge curve, holdingconstant 1.35 V (open circuit) voltage until about the last 5% of their lifetime, when their voltage drops rapidly. The voltage remains within 1% for several years at light load, and over a wide temperature range, making mercury batteries useful as a reference voltage inelectronic instruments and in photographic light meters. Mercury batteries with cathodesmade of a mix of mercuric oxide and manganese dioxide have output voltage of 1.4 V andmore sloped discharge curve. [2]

[edit] Product banThe 1991 European commission directive 91/157, when adopted by member states,

 prohibited the marketing of certain types of batteries containing more than 25 milligrams of 

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mercury, or, in the case of  alkaline batteries, more than 0.025 % by weight of mercury. In1998 the ban was extended to cells containing more than 0.005% by weight of mercury. [5]

In the United States, in 1992 the state of  New Jersey prohibited sales of mercury batteries. In1996 the United States Congress passed the Mercury-Containing and Rechargeable BatteryManagement Act that prohibited further sale of mercury-containing batteries unless

manufacturers provided a reclamation facility, effectively banning the sale. [6]

[edit] SubstitutesThe ban on sale of mercury oxide batteries caused numerous problems for photographers,whose equipment frequently relied on their advantageous discharge curves and long lifetime.Alternatives used are zinc-air batteries, with similar discharge curve, high capacity, but muchshorter lifetime (a few months) and poor performance in dry climates, alkaline batteries withvoltage widely varying through their lifetime, and silver-oxide batteries with higher voltage(1.55 V) and very flat discharge curve, making them possibly the best, though expensive,replacement. Special adapters with a voltage dropping germanium diode are available, toadapt silver oxide batteries for use in older equipment designed for mercury batteries, such as

cameras and light meters which require a stable, exact voltage.

[edit] References