Car Batteries Explained

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21/08/2020

It’s a trope no longer seen in movies: a getaway car for robbers, they get in expecting it will start up, but no. Someone gets out and rotates the crank handle three times.

Crank handle?

Back in the good old days, batteries for cars weren’t a thing. Now, they’re indispensable. However, their call of duty is no longer just for starting the engine, there’s audio systems, aircon, and charging ports for smart devices.

But what is a battery, what is a car battery made of?

The most common type of battery found in a car is called a lead-acid battery. A plastic shell holds a mix of an acidic liquid surrounding lead plates, and like every battery, there are positive and negative charges. The positive plate is lead oxide of PbO2, the negative is pure lead, or Pb.

Fluid wise, the plates sit in a mix of sulfuric acid (H2SO4) and distilled water. Newer forms of technology see this as a gel form, and even a woven glass mat.

A common term that’s heard when referring to car batteries is 12V, or 12 volts. This comes from the structure of a battery having six cells made up of the plates, and each cell provides a charge of just over 2V. The total voltage for a fully charged battery is 12.72V.

Battery plate size comes into play when the Cold Cranking Amperage, CCA, is called upon when starting. This goes a long way to explaining the sheer physical size difference in batteries.

Small engine cars don’t need as much “twist” to fire the cylinders into motion nor as much draw upon a battery’s capacity to fuel the cylinders. Look at a large diesel engine or a big V8, and the battery is substantially larger.

The plates in a battery are what make up a part of how a battery works. Imagine a roof with two solar panels next to a roof with twenty two solar panels. Which one has a greater surface area to soak in the solar energy? It’s akin to the plates in a battery, with the greater amount of plates providing more surface area to the acid. The more plates the greater the CCA.

In order to produce the charge required, the lead plates for the negative charge have powdered sulphates added to the mix that makes up a negative plate. Once the plates have had time to dry and cure they are then stacked in rows of positive and negative, with separator plates that allow charge from the positive to negative but also stop the potential for a short circuit.

As a battery discharges its energy to the engine and associated electrics, a car’s alternator, connected to the spinning engine by a belt, then tops up the battery and modern electronics then keep it at around 12 volts.

There are different types of batteries that are intended for different kinds of applications. If you’re unsure about what you need, contact us today. The Garage Miami supplies high quality batteries from suppliers such as Century and the budget conscious Energi Range.

The Garage Miami is your one-stop-shop for Car Batteries and has the Gold Coast’s best deals on wheels and tyres. Give us a call on 07 5572 1711 so we can answer your questions.

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