Car Batteries: Structure, Function, and Capacity

What is a Car Battery?

The battery is a crucial power supply component in a vehicle. It provides the necessary electrical current to the starter motor, enabling the engine to start. Think of it like a water pump in a water circuit: the pump forces water through pipes to consumers. When the pump sends more water than is consumed, the excess goes into a reservoir, which can then supply consumers. Similarly, a battery provides a consistent power supply, preventing shocks or fluctuations.

Most cars use lead-acid batteries, which convert chemical energy into electrical energy through a process called electrolysis.

Electrolysis Explained

If you immerse two electrodes in distilled water and connect them to a power source with a lamp, the lamp won't light, indicating no current flow. However, if you add salt to the water, the lamp will light up, and its intensity will increase with the salt concentration. An electrolyte is an aqueous solution that allows electrical current to pass through it, causing a chemical reaction.

Battery Structure

A battery consists of a multi-compartment box, often made of acid-resistant ebonite. Each compartment, or cell, contains a series of plates. These plates are constructed using a lead-antimony alloy frame in the shape of a grid, filled with active material.

• Positive Plates: The active material is lead peroxide.
• Negative Plates: The active material is spongy lead.

The grid distributes the current uniformly across the plate. Positive plates are connected via a bridge, and negative plates are connected similarly. Insulators or separators are placed between adjacent positive and negative plates to prevent electrical contact.

Battery Capacity

Battery capacity refers to the amount of energy it can store or deliver when fully charged. It is measured in ampere-hours (Ah).