How Does A Lead Acid Battery Work?


3 Answers

Rajesh Shri Profile
Rajesh Shri answered
A lead acid battery works on the principle of a chemical reaction to produce voltage and current. The process occurs in the following manner: a lead acid battery consists of lead electrodes immersed in a diluted solution of sulphuric acid known as an electrolyte. The electrodes are of two types, the positive electrode being composed of lead dioxide while the negative electrode comprising of soft spongy lead.

A chemical reaction takes place within the battery in which the lead combines with sulphate ions in the solution to produce lead sulphate and free electrons. If a wire is connected between the two terminals the electrons flow to the positive end setting up the flow of current where another reaction is induced which results in the combining of lead dioxide, hydrogen and sulphate ions from the electrolyte and the free electrons produce more lead sulphate and water. Thus the electrolyte slowly gets converted in to water as the battery is discharged while the lead plates get converted in to lead sulphate. The reaction is however reversible and both plates can be regenerated by way of charging.

A load is connected mid way between the battery terminals and a voltage of about 2 volts can be obtained in a conventional single unit of a lead acid battery.
thanked the writer.
Anonymous commented
I got another question related to this one. Without the external wire, why wont the free electrons react with the Hydrogen ions in the electrolyte to form Hydrogen gas? This question arise after reading an article below.

"Probably the simplest battery you can create is called a zinc/carbon battery. By understanding the chemical reaction going on inside this battery, you can understand how batteries work in general.

Imagine that you have a jar of sulfuric acid (H2SO4). Stick a zinc rod in it, and the acid will immediately start to eat away at the zinc. You will see hydrogen gas bubbles forming on the zinc, and the rod and acid will start to heat up. Here's what is happening:

The acid molecules break up into three ions: two H+ (hydrogen) ions and one SO4--(sulfate) ion.
The zinc atoms on the surface of the zinc rod lose two electrons (2e-) to become Zn++ ions.
The Zn++ ions combine with the SO4-- ion to create ZnSO4 (zinc sulfate), which dissolves in the acid.
The electrons from the zinc atoms combine with the hydrogen ions in the acid to create H2 molecules (hydrogen gas). We see the hydrogen gas as bubbles forming on the zinc rod.
If you now stick a carbon rod in the acid, the acid does nothing to it. But if you connect a wire between the zinc rod and the carbon rod, two things change:

The electrons flow through the wire and combine with hydrogen on the carbon rod, so hydrogen gas begins bubbling off the carbon rod.
There is less heat. You can power a light bulb or similar load using the electrons flowing through the wire, and you can measure a voltage and current in the wire. Some of the heat energy is turned into electron motion"
Anonymous Profile
Anonymous answered
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