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Understanding the Working Principle and Uses of a Dry Cell Battery

Dry Cell Battery: Working Principle and Uses
A dry cell battery is a type of chemical battery that uses an electrolyte, which is in the immobilized state. The electrolyte in this cell battery contains very little moisture to allow the passage of current through it. This ScienceStruck post provides the history, definition, composition, uses, and recycling process of the dry cell battery.
Prachi Patkar
Last Updated: Feb 28, 2018
Man Installing Battery Into Lawnmower
Did You Know?
Dry cell battery was being developed in the year 1887 by a scientist named Karl Gassner of German origin. This device was later patented in the year 1982.
Before we begin with understanding the composition and working of a dry cell battery, it is important to understand what a battery is. A battery is a device or an instrument that yields electricity by undergoing certain chemical reactions.

Unlike the wet cell batteries, the dry cell batteries are non-rechargeable. The dry cell battery as the name suggests doesn't carry any type of liquid. Instead it contains a paste which acts as the electrolyte. The cell battery consists of a paste because it is thicker in consistency and thus, will not spill. This battery electrolyte contains little moisture, just enough to allow current to flow through it. Read further to know more about the dry cell battery in detail.
How Does a Dry Cell Battery Work?
The role of any battery is to convert chemical energy to electrical energy. Dry cell battery is a voltage-producing battery, containing the electrolyte chemical in the form of a thick paste. It produces voltage of about 1.5 volts. According to science, an electrode is a conductor used in a battery to run the circuit. It can have positive or negative charge.
Diagram of a Dry Cell Battery
Diagram of a Dry Cell Battery
In the above diagram (which represents the parts of a dry cell battery), the zinc casing provides enclosing to the electrolyte and the cathode as a whole. Ammonium chloride is the electrolyte used in this type of battery. Just ahead of the electrolyte lies manganese dioxide separated from the electrolyte by a separator or partitioning. At the center of the cell battery lies a carbon rod, which is the cathode. Zinc casing is considered as the anode.
Now that we know about the structure and parts of the dry cell battery, let us understand its working. Every portion of the battery device has chemical reactions occurring in it. While a reduction reaction occurs at the carbon electrode, oxidation occurs at the zinc casing, which is the anode. The chemical reactions that define the entire energy generation process are as follows:
The ammonium ion from ammonium chloride reacts with two electrons to produce ammonia and hydrogen gas.

2NH4 (aq) + 2e- ➜ 2NH3 (g) + H2 (g)

The manganese dioxide near the cathode reacts with the hydrogen gas liberated to form Manganese(III) oxide and water.

2MnO2 (s) + H2 (g) ➜ Mn2O3 (s) + H2O (l)

Combining equation I and II we get,

2NH4 (aq) + 2MnO2 (s) + 2e- ➜ Mn2O3 (s) + 2NH3 (g) + H2O (l)

The half-reaction occurring at the zinc anode is:

Zn (s) ➜ Zn2+ + 2e-

Combining all the above equations we get,

Zn (s) + 2MnO2 (s) + 2NH4 (aq) ➜ Mn2O3 (s) + H2O (l) + Zn2 + 2NH3 (g)

Due to these reactions, chemical energy gets converted into electrical energy. This energy then flows from the battery to the connected device through the outer circuit.

Note:
1) Zinc chloride can be used as a substitute to ammonium chloride.
2) Carbon is sometimes used as an addition to manganese dioxide.
Dry cell battery is available in a variety of sizes such as AA, AAA, C, D, and 9 volts. Its use depends primarily on its size. While the small-sized batteries are used for watches or calculators, the comparatively bigger-sized ones are used in radios and flashlights. Besides the commonly used zinc-carbon battery, other examples of dry cell batteries are PP3 batteries (also known as transistor radio battery), Lithium-Ion, Nickel/Cadmium, and Nickel Metal Hydride batteries.
Testing a Dry Cell Battery
Multimeter and AA battery
Things you need:
• Multimeter
• AA battery

1) Multimeter should be set to read the voltage.
2) The red probe tip should be touched to the top of the battery, whereas that of the black probe should be touched to the bottom of the battery.
3) The multimeter should display the voltage reading of 1.5 volts. If it does, it indicates that the battery is in a good condition. Even a slight variation indicates that the battery needs to be replaced.
Uses
Remote control batteries
➢ The batteries larger in size are used in flashlights, remote controls, radios, etc. The ones that are smaller in size are used in wrist watches, video games, calculators, hand-held electronic devices, etc.
Wrist watch batteries
➢ They are used in small motors (mainly hard disks, wheelchairs, etc) and large motors (mainly marine, automotive, etc).
Advantages of a Dry Cell Battery
➢ They have lower prices as compared to the wet cell batteries.

➢ The electrolyte being a thick paste is free from movement. Thus, these batteries last longer.

➢ Their most important advantage is their small size and compact shape. This makes them portable and apt for small-sized devices.

➢ They do not contain liquid electrolytes. This makes them have lighter weights than their wet cell counterparts.

➢ They do not pose any threat to the environment as they do not contain any substance having a corrosive nature.
Recycling Process
Dry cell batteries are of primary and secondary types. While the primary ones cannot be replenished by charging, the secondary can be charged. Thus, the primary must be disposed off when they cease to work. Although they are not known to be hazardous to the nature, their disposal must be done in the right way. The alkaline batteries can be disposed along with the regular trash. Another very pertinent solution to this problem can be resorting to the use of secondary dry cell batteries. This will allow recharging and reusing the batteries, thus, reducing the junk.
Although dry batteries have relatively low charge-producing capacity, they find a number of uses in smaller devices requiring less power. And as the proverb goes In unity lies strength, a number of dry cell batteries coupled together provide larger amount of voltage.