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Car Batteries: How They Work

The lead battery is one of the most important parts of the modern car, and understanding it is crucial to performing a car service. In this article, we’ll provide a brief introduction to how the car battery works and run through a few of the problems that could go wrong with it at any time.

A car battery has two terminals — one is positive and one is negative. These terminals are connected to the car and power a range of your car’s important functions, including:

  • Starting the engine
  • Air conditioning
  • Playing the radio
  • Turning on the headlights
  • Running windscreen wipers

Every car battery is made up of six cells. Each cell possesses two electrodes made of eight overlapping metal plates. These eight overlapping metal plates form what is known as a “grid”, making a total of two grids and 16 plates per cell. It is through these cells that the energy to power your car is produced. But how does it work?

Well, first, let’s recap…

  • A battery is made of six cells
  • Each cell is made of two grids
  • Each grid is made of eight overlapping metal plates

A little bit of chemistry…

It’s all about chemical reactions. One of the grids is positive, while the other is negative. The positive grid is covered in lead oxide and brings electrons into the cell. The negative grid, which is covered in lead, releases the electrons.

The metal plates — remember, eight of them in each grid, 16 in each cell — are soaked in a mixture of water and sulphuric acid. (It’s only about 35 per cent sulphuric acid, but that’s more than enough to burn through clothes and severely burn your skin. It’s a powerful concoction.) This mixture acts as an electrolyte — a substance that conducts electricity.

When the sulphuric mixture reacts with the lead oxide on one grid and the lead on the other, electron particles are released. As they race around the grids, electricity is created. The electrons make their way from the positive grid in the first cell and then out the negative grid, into the next cell. By the time the electrons have passed through all six cells, 12 volts of electricity have been created.

What can go wrong with a car battery?

There are various things that can go wrong with a car battery. If you’re finding that your battery is going dead every morning — and you’re certain you haven’t drained it by leaving your headlights or radio on, for example — then problems may include:

  • Low electrolyte levels (not enough of the sulphuric acid/water mixture in the cells)
  • Dirty or corroded battery terminals (This stops the flow of electricity into the battery in the first place)
  • Deteriorated lead oxide plates (This means the battery needs replacing)

Also, if you turn the key to start the engine but hear nothing but a clicking sound, this means your battery lacks the power to engage the starter motor. This could be due to incomplete charging by the alternator. Dealing with problems with your battery is best left to a qualified mechanic , who has the tools and expertise required to both diagnose and treat the battery problem.

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