Various Types of Batteries

Batteries can be divided into two major divisions, primary batteries and secondary batteries. A primary battery is one which is disposed off once used and cannot be recharged. Secondary batteries are rechargeable batteries. The charging and discharging can happen many times depending on the battery type. Alkaline batteries, Mercury batteries, Silver-Oxide batteries, and

Zinc carbon batteries are examples of primary batteries whereas Lead-Acid batteries and Lithium batteries fall into the secondary batteries category.

• Alkaline Batteries

  • Alkaline batteries are non-rechargeable and high energy density batteries that are designed for long lasting performance.
  • This battery obtained its name because the electrolyte used in it is alkaline (potassium hydroxide).
  • The typical values of voltage and current supplied by a single alkaline cell are 1.5V and 700mA respectively.
  • Alkaline batteries are the most common type of batteries used in the world. Applications include remote controls, clocks, and radios. Due to high run time these are ideal for digital cameras, hand held games, MP3 players etc.

• Zinc-Carbon Batteries

  • Zinc-Carbon batteries are also known as dry cells which come in a composition of a carbon rod (cathode) packed in a zinc container acting as the anode. The electrolyte is a mixture of ammonium chloride and zinc chloride.
  • The typical voltage value is a little less than 1.5V.
  • These batteries are durable and have longer lives.
  • Zinc-Carbon batteries can be used effectively at moderate temperature but do not work well at low temperatures.
  • These general purpose batteries are available for lower prices. The basic use is in low power drain applications such as flash lights, remote controls, toys, and table clocks.

• Mercury Batteries

  • Mercury batteries are non-rechargeable batteries that contain mercuric oxide with manganese dioxide.
  • They are deep discharge batteries and voltage level does not fall below 1.35V until 5% energy level is reached. These batteries are less popular because of low output voltage. Furthermore, mercury is toxic and can cause hazards for humans.
  • The flat discharge curve makes this battery useful for photographic light meters and electronic devices such as to run the real-time clock of CPU.

• Silver Oxide Batteries

  • Silver oxide batteries are expensive, long life batteries small to large sized primary cells that offer better run time than alkaline batteries.
  • They are usually suitable for powering low-current electrical devices like calculators, iPods, digital diaries, wrist watches, stop watches and artificial pacemakers.
  • They are also used in military and submarine applications.

• Lead-Acid Batteries

  • Lead-acid batteries are the rechargeable kind of batteries invented in the 1980s.
  • These large, heavyweight batteries find the major application in automobiles as these fulfill the high current requirements of the heavy motors.
  • The major application of lead acid battery is in starting, lightning and ignition systems (SLI) of automobiles and portable emergency lights.
  • Its other form, wet cell battery is used as backup power supply for high end servers, personal computers, telephone exchanges, and in off-grid homes with inverters.

• Lithium Batteries

  • Lithium batteries are rechargeable batteries, where lithium in its pure ion compound form is used.
  • Depending on the design and chemical compounds used, lithium batteries can produce voltages from 1.5 Volts to 3.7 Volts. Compared to ordinary zinc–carbon batteries or alkaline batteries, the voltage production of lithium cell is twice.
  • The most common type of lithium battery used in consumer applications uses manganese dioxide as cathode and metallic lithium as anode.
  • Lithium cells can also be used as a replacement of alkaline batteries in many devices, such as cameras and clocks.

Working of Lead-Acid Battery

• The composition of Lead-Acid battery is a combination of Pb (negative) and $PbO_2$ (positive) as electrodes, with $H_2SO_4$ as electrolyte in charged form and $PbSO_4$ and water in discharged form.
• The main active materials of a lead-acid battery are:

1. Lead peroxide $(PbO_2)$ - The positive plate is made of lead peroxide.
2. Sponge Lead (Pb) - The negative plate is made of pure lead in soft sponge condition.
3. Dilute Sulfuric Acid $(H_2SO_4)$ - Dilute sulfuric acid used for lead acid battery has ratio of water : acid =3:1.

• The lead acid storage battery is formed by dipping lead peroxide plate and sponge lead plate in dilute sulfuric acid. A load is connected externally between these plates.
• In diluted sulfuric acid the molecules of the acid split into positive hydrogen ions (H+) and negative sulfate ions $(SO_4^{2−})$. The hydrogen ions when reach at $PbO_2$ plate, they receive electrons from it and become hydrogen atom which again attack PbO2 and form PbO and $H_2O$ (water). $$PbO_2+2H -→PbO+H_2 O$$
• This PbO reacts with $H_2 SO_4$ and forms $PbSO_4$ and $H_2O$ (water). $$PbO+ H_2 SO_4 -→PbSO_4+H_2 O$$
• $SO_4^{2−}$ ions are moving freely in the solution so some of them will reach to pure Pb plate where they give their extra electrons and become radical $SO_4$. As the radical $SO_4$ cannot exist alone it will attack Pb and will form $PbSO_4$. As H+ ions take electrons from $PbO_2$ plate and $SO_4^{2−}$ ions give electrons to Pb plate, there would be an inequality of electrons between these two plates. Hence there would be a flow of current through the external load between these plates for balancing this inequality of electrons. This process is called discharging of lead acid battery.
• Then the load is disconnected and we connect $PbSO_4$ covered $PbO_2$ plate with positive terminal of an external DC source and $PbO_2$covered Pb plate with negative terminal of that DC source. During discharging specific gravity of sulfuric acid solution falls due to formation of water during reaction at $PbO_2$ plate. But there is still sulfuric acid existing in the solution. This sulfuric acid also remains as H+ and $SO)4^{2−}$ ions in the solution. Hydrogen ions (cation) being positively charged, move to the electrode (cathode) connected with negative terminal of the DC source. Here each H+ ion takes one electron from that and becomes hydrogen atom. These hydrogen atoms then attack $PbSO_4$ and form lead and sulfuric acid. $$PbSO_4+2H-→ Pb+ H_2 SO_4$$
• $SO_4^{2−}$ ions (anions) move towards the electrode (anode) connected with positive terminal of DC source where they give up their extra electrons and become radical $SO_4$. This radical SO4 cannot exist alone hence reacts with $PbSO_4$ of anode and forms lead peroxide $(PbO_2)$ and sulfuric acid $(H_2SO_4)$. $$PbSO_4+2H_2+SO_4 -→ PbO_2+ 2H_2 SO_4$$
• Hence by charging the lead acid storage battery cell, Lead sulfate of anode gets converted into lead peroxide. Lead sulfate of cathode is converted to pure lead. Terminal potential of the cell increases. Specific gravity of sulfuric acid increases.

The battery is the main part of the electrical system in an automobile. Without battery, engine cannot be started with the starting motor. Since it serves as reverse source of electricity to operate whole of the electrical equipment. The battery is storage of energy. It gets electrical energy from dynamo. This electrical energy is converted into chemical energy & stored in the battery. This energy can be made available at any time.

The type of batteries are following:
i) lead-acid battery
ii) Alkaline battery
a). Nickel iron type b). Nickel cadmium type
iii) Zinc air battery
iv)ZEBRA battery
v) Sodium Sulphur battery

Lead-acid battery :
There are few cells in the lead acid battery. Each cell contains lead plates. The negative plate is spongy lead. It is gray in colour. The positive plate is lead peroxido which is brown in colour. These plates are kept immersed in dilute sulphuric acid. There are separators to keep the positive & negative plates apart. These separators are made of a non conducting porous material & prevent short circuits.
The chemical reaction takes place between the three chemicals in the battery. In presence of $H_SO_4$, the electrons from one group of plate collect on the other group of plate. This flow of electrons is continuing until there is insufficient imbalance of electron to create a 2 volts between the terminal of the battery cell. If two terminals are connected by a circuit the electron will flow. After a certain amount of current has been withdrawn, the battery is discharged or dead. When it is discharged, it is not capable of delivering any additional current. It is then charged. The chemical reaction takes place while the battery is charged & discharged:

$\,\,\,\,\,\,\,\,PbO_2\hspace{0.5cm}+\hspace{0.5cm}2H_2SO_4\hspace{0.5cm}+\hspace{0.5cm}Pb \,\,\,\hspace{0.5cm}-\gt\hspace{0.5cm}\,\,\,\hspace{0.5cm}PbSO_4\hspace{0.5cm}+\hspace{0.5cm}2H_2O\hspace{0.5cm}+\hspace{0.5cm}PbSO_4\hspace{0.5cm}+\hspace{0.5cm}Q$

$lead\,peroxide \,\,\,\, sulphuric\, acid \,\,\,\, \,\,\,\,\,\ lead \,\,\,\, \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, lead\, sulphate \,\,\,\,\,\,\,\,\,\,\,\, water \,\,\,\,\,\,\,\,\,\,\,\, lead\, sulphate \,\,\,\,\,\ Energy$

During discharging_of_battery, the sulphuric acid $H_2SO_4$ is split into hydrogen $H_2$ & sulphate $SO_4$. The hydrogen literate at the lead oxide (PbO) which combine with part of sulphuric acid to form lead sulphate$(PbSO_4)$.

The sulphate is liberated at the spongy lead plates(Pb) & combine with them to form lead sulphate $(PbSO4)$. During this process the electrolyte become dilute because of the absorption of $SO4$ by the sponge lead plates. When battery is charged , the chemical reaction shown above become reverse. The lead sulphate on the plate again converts to lead peroxide & the lead sulphate on the other plate is reduced to spongy lead Pb. Thus three electrolyte becomes concentrated because of increase in $H2SO4.$ Thus, the battery converts electrical energy into chemical during charging & chemical energy into electrical energy during discharging.