How Does a car batteries work?

 Just like your TV remote or fancy electric toothbrush, your car needs a battery to function. When it dies, your car won’t start, leaving you either stranded or stuck at home. You know your car battery is important, but do you really understand how it powers your engine, lights, and radio? Follow along as we break down the complexities of a battery and explain how car batteries work! If knowledge is power, you’re going to be in great shape.

 

 

What’s a battery?

Before jumping into the complexities of car batteries, let’s look at how batteries in general function. According to the folks at NASA, a battery is “a device that Convert chemical energy into electricity.” Batteries are composed of cells. These cells are what contain the actual energy. They store chemical energy and transform it into electrical energy on command. That’s what powers your devices, from your TV remote to your electric toothbrush.

How do car batteries work?

Most car batteries rely on a lead-acid chemical reaction to get things moving and grooving. These batteries fall into the “SLI” category. SLI stands for “starting, lighting, and ignition.” This type of battery provides short bursts of energy in order to power your lights, accessories, and engine. Once the battery jolts the engine to life, power for the car is supplied by the alternator. Most vehicles come with a generic SLI battery from the factory.

How car batteries work:

1. A typical SLI battery has six cells. Each cell has two plates, or grids: one is made of lead, the other of lead dioxide. Each cell is able to produce about 2-volts of energy. In most car batteries you have six cells, and therefore a 12-volt battery.
2. The plates are submerged in sulphuric acid that triggers a reaction between the two plates. In scientific terms, the acid acts as a catalyst.
3. This acid will trigger a reaction on the lead dioxide plate, causing the plate to produce two things: ions and lead sulphate.
4. The ions produced by the lead dioxide plate react to the adjacent plate to produce hydrogen and lead sulphate.
5. The result is a chemical reaction that produces electrons. The electrons race around the plates and generate electricity. The electricity flows out of the battery terminals to start your engine, turn on your headlights, and play the radio.
6. This chemical reaction is entirely reversible, which is why you can jumpstart your battery and continue to charge it throughout the duration of its life. By applying current to the battery at just the right voltage, lead and lead dioxide will form on the plates and you can reuse your battery, over and over again!

 

 

Battery Voltage

Voltage refers to the amount of electrical potential your battery holds. The standard automotive battery in today’s vehicles is a 12-volt battery. Each battery has six cells, each with 2.1 volts at full charge. A car battery is considered fully charged at 12.6 volts or higher.

When the battery’s voltage drops, even a small amount, it makes a big difference in its performance. The table on the left shows how much energy remains in a battery as the battery voltage reading changes.

Though not fully charged, a car battery is considered charged at 12.4 volts or higher. It is considered discharged at 12.39 volts or less.

Chemical Reaction

Electrical energy in a battery is generated by a chemical reaction. In the case of a lead-acid battery, a mixture of sulfuric acid and water, known as electrolyte, reacts with active material inside the battery.

A battery’s voltage largely depends on the concentration of sulfuric acid. To get a voltage of 12.6 volts or higher, the weight percentage of sulfuric acid should be 35 percent or more.

As a battery is discharged, the reaction between sulfuric acid and active material forms a different compound and the concentration of sulfuric acid declines. Over time, this causes the battery’s voltage to drop. 

 

 

Cranking Power

Vehicle engines require cranking power to start. The power needed depends on many factors, such as engine type, engine size and temperature. Typically, as temperatures drop, more power is needed to start the engine. Cold cranking amps (CCA) is a rating that measures a battery’s cranking power. It refers to the number of amps a 12-volt battery can deliver at 0°F for 30 seconds while maintaining a voltage of at least 7.2 volts. For example, a 12-volt battery with a 600 CCA rating means that at 0°F, the battery will provide 600 amps for 30 seconds without dropping below 7.2 volts.